EIGHT-HOUR OZONE ATTAINMENT PLAN 

FOR SAN DIEGO COUNTY 

May 2007

SAN DIEGO COUNTY 

AIR POLLUTION CONTROL DISTRICT 

10124 OLD GROVE ROAD 

SAN DIEGO, CA 92131
EIGHT-HOUR OZONE ATTAINMENT PLAN 

FOR SAN DIEGO COUNTY 

TABLE OF CONTENTS 

PAGE

1.0 INTRODUCTION AND OVERVIEW ............................................................................. 1-1

1.1 Background ..................................................................................................................................1-1 

1.1.1 What is Ozone?...................................................................................................................1-1 

1.1.2 Health and Welfare Effects.................................................................................................1-2 

1.1.3 Federal Ozone Air Quality Standards .................................................................................1-2 

1.1.4 Ozone Designation Status...................................................................................................1-3 

1.2 Emission Sources .........................................................................................................................1-4 

1.3 Emission Control Efforts..............................................................................................................1-4 

1.4 Ozone Air Quality Improvement..................................................................................................1-5 

1.4.1 Most Improved in the Nation..............................................................................................1-6 

1.4.2 Transported Pollution .........................................................................................................1-7 

1.5 Attainment Planning Requirements..............................................................................................1-7 

1.5.1 2006 Appeals Court Decision and Implications .................................................................1-8 

1.5.2 Subpart 1/Basic Nonattainment Area Requirements...........................................................1-8 

1.5.3 Subpart 2/Moderate Nonattainment Area Requirements ..................................................1-10 

1.5.4 Attainment Finding Versus Attainment Demonstration ...................................................1-11 

2.0 EMISSION INVENTORIES AND TRENDS................................................................... 2-1

2.1 Inventory Development Process...................................................................................... 2-1

2.2 Inventories for 2002 Base Year and 2008 Attainment Year.........................................................2-1 

2.3 Long-Term Emission Trends........................................................................................................2-2 

2.4 Emission Budgets .........................................................................................................................2-4 

2.4.1 On-Road Motor Vehicle Emission Budgets for Transportation Conformity......................2-4 

2.4.2 Military Growth Increment for General Conformity ..........................................................2-5

2.5 Pre-Baseline Banked Emission Credits ........................................................................................2-6

3.0 EMISSION CONTROL STRATEGY .............................................................................. 3-1

3.1 Summary ......................................................................................................................................3-1 

3.2 Existing Control Strategy .............................................................................................................3-1 

3.2.1 State and Federal Control Programs ...................................................................................3-1

3.2.2 Local Control Measures......................................................................................................3-5 

3.3 Additional New Control Measure – Low VOC Solvent Cleaning ...............................................3-7 

3.4 Reasonably Available Control Measures (RACM) ......................................................................3-7 

3.4.1 RACM Requirements..........................................................................................................3-7 

3.4.2 Identifying Potential RACM for Stationary Sources ..........................................................3-8 

3.4.3 Identifying Potential RACM for Transportation Sources.................................................3-10 

3.4.3.1 Implementation Status of Transportation Control Measures...................................3-12 

3.4.3.2 Emission Reduction Potential of Transportation Control Measures .......................3-16 

3.4.4 RACM Analysis................................................................................................................3-16 

Eight-Hour Ozone Attainment Plan
4.0 ATTAINMENT DEMONSTRATION.............................................................................. 4-1

4.1 Background ..................................................................................................................................4-1 

4.2 Results ..........................................................................................................................................4-2 

4.3 Modeled Attainment Test.............................................................................................................4-2 

4.3.1 Episodes..............................................................................................................................4-2

4.3.2 Model-Predicted 2008 Design Value..................................................................................4-4 

4.4 Weight of Evidence Demonstration .............................................................................................4-4

4.4.1 Weight of Evidence Analyses Involving Modeling Results ...............................................4-5 

4.4.1.1 Unmonitored Area Analysis......................................................................................4-5 

4.4.1.2 Modeled Ozone Exposure Reduction Metric ............................................................4-6 

4.4.2 Air Quality Trends Data......................................................................................................4-7 

4.4.2.1 Eight-Hour Ozone Design Values Trends Statistical Analyses.................................4-7 

4.4.2.2 Graphical Air Quality Trends Analyses ..................................................................4-11 

4.4.3 Meteorological Representativeness of Recent Years........................................................4-11 

4.4.4 Emission Trends................................................................................................................4-12 

4.4.5 Shortened Ozone Season...................................................................................................4-13 

4.5 Conclusion..................................................................................................................................4-14 

5.0 CONTINGENCY MEASURES......................................................................................... 5-1

ATTACHMENTS

Attachment A  Emission Inventories for 2002 and 2008 ................................................. A-1 

Attachment B  Planned Military Projects Subject to General 

Conformity.............................................................................................................................B-1 

Attachment C  Pre-Baseline Banked Emission Credits ....................................................C-1 

Attachment D  Analyses of Potential Additional Stationary Source Control Measures.. D-1 

Attachment E  Calculation of Cumulative Potential Emission 

Reductions for Possible Reasonably Available Control 

Measures....................................................................................................E-1 

Attachment F  Graphical Air Quality Trends Analyses ...................................................F-1 

Attachment G  Meteorological Representativeness of Recent Years .............................. G-1 

Attachment H  Meteorological and Photochemical Modeling for the San Diego County 

2007 Eight-Hour Ozone State Implementation Plan................................ H-1 

Eight-Hour Ozone Attainment Plan
1.0 Introduction and Overview

1.0 INTRODUCTION AND OVERVIEW

Federal clean air standards have been established for common outdoor air pollutants, including 

ozone, to protect public health and the environment from the harmful effects of air pollution. These 

standards, called National Ambient Air Quality Standards (NAAQS), are established by the U.S. 

Environmental Protection Agency (EPA) pursuant to requirements of the federal Clean Air Act 

(CAA).1 Each area of the nation with air pollution levels violating a NAAQS must be designated 

by EPA as a “nonattainment area” for that pollutant. Each nonattainment area must submit a “State 

Implementation Plan” (SIP) outlining the combination of local, State, and federal actions and 

emission control regulations necessary to bring the area into attainment as expeditiously as 

practicable. 

San Diego County is currently designated a Nonattainment Area for the eight-hour ozone NAAQS. 

By June 15, 2007, the San Diego County Air Pollution Control District (APCD) must submit to 

EPA, through the California Air Resources Board (ARB), a SIP identifying control measures and 

associated emission reductions as necessary to demonstrate attainment by June 15, 2009. This 

Eight-Hour Ozone Attainment Plan addresses and complies with these requirements. 

1.1 BACKGROUND 

1.1.1 What is Ozone?

Ozone is a corrosive gas composed of three oxygen atoms linked together. Ozone exists in two 

layers of the atmosphere. It occurs naturally in the stratosphere (upper atmosphere) where it 

absorbs and provides a protective shield against the sun’s damaging ultraviolet radiation. Ozone 

also exists in the troposphere (lower atmosphere), even near ground level, as a result of various 

human activities. “Ground level” ozone—the subject of this Attainment Plan—is an air pollutant 

that can damage living tissue and break down certain materials. 

Ozone is not usually emitted directly into the air, but at ground level is formed by chemical 

reactions of “precursor” pollutants—oxides of nitrogen (NOx) and volatile organic compounds 

(VOC)—in the presence of ultraviolet radiation (strong sunlight). NOx and VOC emissions are 

mostly the result of various human activities such as fossil fuel combustion and solvent use. 

However, there are also natural sources of VOC emissions (such as trees) and NOx emissions (such 

as forest fires). Consequently, there are natural background levels of ozone, at levels shown to be 

well tolerated. 

Ozone levels are usually higher during the spring and summer months. Abundant sunshine 

promotes ozone formation and warm weather increases VOC emissions (an ozone precursor) from 

fuel and solvent evaporation. Additionally, warm weather is often associated with stable 

atmospheric conditions and an inversion layer2 in the lower atmosphere, reducing dispersion of 

ozone. 

 

1 Federal Clean Air Act requirements are codified, as amended, in the U.S. Code at 42 U.S.C. Sections 7401, et seq. 

2 An inversion layer is a stable layer of the atmosphere, which does not allow for upward air motion. An inversion 

often acts like a cap on the atmosphere, trapping air pollution below it. 

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1.0 Introduction and Overview

Concentrations of ozone are not uniform; the amount of ozone in the lower atmosphere varies by 

hour, day, and place. Ozone molecules in urban areas persist for less than a day, with 

concentrations usually peaking in mid to late afternoon, after exhaust fumes from morning 

commutes have had time to react fully in the sunlight. By early evening, ozone production drops as 

the sunlight's intensity decreases and exhaust fumes from evening commutes react with and break 

down most of the remaining ozone. This entire cycle repeats itself the following day. 

1.1.2 Health and Welfare Effects

A significant body of research has shown that exposure to unhealthful levels of ozone can cause 

lung and airway inflammation, significant decreases in lung function and capacity, and other 

respiratory symptoms such as cough and pain when taking a deep breath. Ozone exposure is a 

particular threat during the summer ozone season for people working, exercising, or playing 

outdoors or who already have respiratory problems. Long-term exposure to moderate levels of 

ozone may cause permanent changes in lung structure, leading to premature aging of the lungs and 

worsening of chronic lung disease. 

Plants and crops are also impacted by ground level ozone, slowing plant growth and increasing 

susceptibility to disease, pests, and harsh weather. The reduced yield hurts the agricultural and 

forest industries. 

Scientific and medical research continue to uncover new information on the effects of ozone air 

pollution. The California Air Resources Board has prepared a summary of recent research and 

findings, available on their website at www.arb.ca.gov/research/health/fs/PM-03fs.pdf. 

1.1.3 Federal Ozone Air Quality Standards

Eight-Hour Ozone NAAQS. The eight-hour ozone NAAQS was established by EPA in 1997.3 It 

is attained when the “three year average” of the “annual fourth highest daily maximum” eight-hour 

average ozone concentration—called the “design value”—is no greater than 0.084 parts per million 

(ppm) at each EPA-approved ozone air quality monitor in the region. The “three-year average” and 

“annual fourth highest daily maximum” are statistical values that provide stability to the standard, 

moderating the influence of extreme meteorological conditions (over which an area has no control) 

that could cause the region’s ozone compliance status to vacillate between attainment and 

nonattainment despite ongoing emission reductions. 

One-Hour Ozone NAAQS. A one-hour ozone NAAQS (0.12 ppm) was established by EPA in 

1979.4 This ozone standard was attained in San Diego County in 2001,5 the culmination of decades 

of emission reduction efforts. Attainment was achieved despite substantial growth in the region’s 

population and motor vehicle fleet, clearly demonstrating that emission control efforts in San Diego 

County are working. (Refer to Section 1.4 for additional information on emissions and regional 

growth trends.) One-hour ozone attainment was achieved by reducing emissions of ozone 

precursors NOx and VOC, setting the stage for continuing efforts to attain the more healthprotective eight-hour ozone NAAQS. 

 

3 Federal Register, Volume 62, Page 38856 (62 FR 38856). 

4 44 FR 8202. 

5 67 FR 65043. 

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1.0 Introduction and Overview

The one-hour ozone NAAQS was revoked by EPA, effective June 15, 2005.6 Although the onehour standard has been phased out, associated emission control requirements in place on the date of 

revocation continue to apply pursuant to anti-backsliding provisions of the CAA (Section 172(e)). 

1.1.4 Ozone Designation Status

The region’s air quality designations for the NAAQS (attainment, nonattainment, or unclassifiable) 

are listed in federal regulation.7 San Diego County was designated a Nonattainment Area for the 

eight-hour ozone NAAQS, effective June 15, 2004, based on ozone air quality measurements over 

the 2001-2003 three-year period.8 At that time, the region’s nonattainment status was further 

categorized by EPA as “Basic,” a category of eight-hour ozone nonattainment areas whose one-hour 

ozone design values meet the former one-hour ozone NAAQS. 

Boundaries of Nonattainment Area. The outer boundaries of the San Diego Nonattainment Area 

are contiguous with the boundaries of San Diego County, as illustrated in Figure 1-1. 

FIGURE 1-1 

San Diego Nonattainment Area Boundaries 

For the Eight-Hour Ozone NAAQS 

<http://www.epa.gov/ozonedesignations/areamaps/SanDiego.pdf> 

 

6 70 FR 44470. 

7 40 CFR 81.305, “Designation of Areas for Air Quality Planning Purposes – California.” 

8 69 FR 23858. 

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1.0 Introduction and Overview

Tribal Nations. The Campo, Cuyapaipe, La Posta, and Manzanita Indian Reservations (near the 

southeast corner of the county) are excluded from San Diego’s Nonattainment Area designation, 

and are designated as Attainment Areas. In fact, pursuant to federal requirements, none of the 

region’s Tribal Nations are regulated by the District and their ozone status does not affect this 

Eight-Hour Ozone Attainment Plan, which applies to non-tribal land only. 

1.2 EMISSION SOURCES

Ground level ozone is formed by complex chemical reactions of NOx and VOC emissions in the 

presence of sunlight. NOx is emitted mostly from sources of fossil fuel combustion, including 

motor vehicles, other mobile sources (such as ships, trains, and aircraft), power plants, and piston 

engines. VOC emissions are released from fuel combustion as well as fuel and solvent evaporation. 

Sources of VOC emissions include motor vehicles, gas stations, chemical plants, factories, landfills, 

and consumer and commercial products. (Natural sources of VOC and NOx emissions also exist, as 

indicated in Section 1.1.1.) 

The percentage contribution of ozone-forming emissions by manmade source type in San Diego 

County is presented in Figure 1-2. Mobile sources, which are under State and federal jurisdiction, 

produce over three-quarters of ozone-forming emissions regionwide. Stationary industrial facilities 

and consumer and home products contribute to a lesser extent. A complete inventory of emission 

sources in San Diego County is presented in Section 2.0 (Emission Inventories and Trends) and 

Attachment A. 

FIGURE 1-2 

Manmade Sources of Ozone-Forming Emissions 

(VOC+NOx) 

San Diego County, 2002 Base Year 

Based on ARB SIP emissions inventory. 

1.3 EMISSION CONTROL EFFORTS 

Air quality control in California is a shared responsibility among local, State, and federal agencies. 

Local air districts regulate emissions from non-mobile (stationary) sources, such as stationary 

Eight-Hour Ozone Attainment Plan Page 1-4
1.0 Introduction and Overview

industrial and commercial sources, and some area-wide sources such as coatings and industrial 

solvents. At the State level, ARB adopts measures to reduce emissions from on-road motor 

vehicles, off-road vehicles and equipment, fuels, and consumer products. At the national level, 

EPA regulates off-road equipment and inter-state sources such as ships, trains, aircraft, and out-ofstate vehicles. 

APCD—in collaboration with federal, State, and local agencies and the citizens, businesses, and 

civic groups of San Diego County—has worked hard to efficiently and cost-effectively reduce 

ozone precursor emissions from nearly every source to ensure cleaner air for all San Diegans. 

Summaries of State and federal control programs and associated regulations are presented in 

Section 3.2.1. The District has adopted dozens of emission control rules addressing all significant 

stationary source categories in San Diego County (see Section 3.2.2). These rules implemented 

previous local planning efforts to attain the NAAQS (such as for the former one-hour ozone 

standard), coupled with State requirements for adopting every feasible control measure for sources 

under District jurisdiction. As a result of shared efforts, San Diego’s motor vehicles, power plants, 

factories, gas stations, engines, paints, and solvents are among the cleanest in the nation. 

Total regionwide NOx and VOC emissions have been reduced 32% and 46% respectively over the 

1990-2005 period (see Section 2.0, Emission Inventories and Trends).9 Further, ongoing 

implementation of existing rules and regulations will continue reducing total regionwide ozone 

precursor emissions for the foreseeable future, as future-year requirements become effective and as 

new lower-emitting sources replace older, higher-emitting sources at the end of their useful lives. 

Because ozone-precursor control efforts in the region are working effectively and will continue to 

provide emission benefits, and because San Diego County’s ozone air quality is now close to 

attaining the eight-hour ozone NAAQS (see Sections 1.4 and 4.4), the strategy to attain as 

expeditiously as practicable relies heavily on the existing District, State, and federal programs and 

regulations. The Emission Control Strategy is discussed in detail in Section 3.0. 

1.4 OZONE AIR QUALITY IMPROVEMENT 

The District operates an extensive air monitoring network, continuously monitoring ambient levels 

of ozone (and many other air pollutants) at numerous sites throughout the region (Figure 1-3) in 

compliance with federal requirements.10 Data generated at these monitors are used to define the 

nature and severity of ozone and to determine NAAQS attainment status in San Diego County. 

 

9 Based on ARB SIP emissions inventory, Version 1.06. 

10 40 CFR Part 58, “Ambient Air Quality Surveillance.” 

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1.0 Introduction and Overview

FIGURE 1-3 

Ozone Monitor Locations in San Diego County 

1.4.1 Most Improved in the Nation

Although the eight-hour ozone NAAQS was not established until 1997, monitoring data since 1990 

show a long-term trend toward attainment even while the region experienced substantial growth in 

population and vehicle miles traveled, as illustrated in Figure 1-4. Improvements in ozone air 

quality generally track with reductions in ozone-forming emissions, providing more evidence that 

emission control programs are successful. In fact, in 2005 the region distinguished itself as the 

most improved metropolitan area in the nation for reduction in exceedances of the eight-hour ozone 

NAAQS between 1990 (96 exceedances) and 2004 (eight exceedances). Only one monitoring 

location (Alpine) has violated the eight-hour ozone standard since 1998. 

FIGURE 1-4 

Emissions and Growth Trends in San Diego County 

0

20

40

60

80

100

199019921994199619982000200220042006

Vehicle Miles Traveled

(millions/day)

Countywide Population

(100,000's)

Ozone Forming Emissions

(tons/day/10)

Days Over Federal 8-Hour

Ozone Standard

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1.0 Introduction and Overview

1.4.2 Transported Pollution

San Diego’s ozone air quality problem is complicated by transported air pollution from the South 

Coast Air Basin, located immediately north and upwind of San Diego County.11 South Coast 

suffers the worst ozone problem in the nation, notwithstanding tremendous ozone air quality 

improvement over the past two decades. This transported air pollution, over which the District has 

no control, often increases ozone concentrations measured downwind at San Diego’s monitoring 

sites. Since 2003, transport has played a significant role in all of the county’s exceedances of the 

eight-hour ozone NAAQS, as determined by meteorological analyses of ozone exceedances. 

Transported air pollution from South Coast to San Diego follows several different known routes: 

1. Transport Aloft. Ozone is transported aloft from South Coast when winds from the north 

move ozone trapped aloft within the inversion layer southward into San Diego County. This 

transported ozone aloft most often impacts the Alpine monitoring site, in the inland foothills 

at an elevation of approximately 2,000 feet. The Alpine monitor is the only monitoring site 

in San Diego County with eight-hour ozone design values exceeding the NAAQS. 

2. Coastal Transport. Coastal transport can occur when relatively mild Santa Ana winds 

blowing toward the southwest push South Coast’s air pollution over the ocean, and the sea 

breeze transports air pollution onshore into San Diego County, impacting the coastal 

monitoring sites. 

3. Inland Transport. Inland transport can occur when air pollution from South Coast’s inland 

areas blows into San Diego County generally along the Interstate 15 freeway corridor. 

Importantly, the South Coast Air Quality Management District (SCAQMD) has implemented an 

effective emissions control program resulting in a long-term trend of emission reductions and ozone 

air quality improvement in the South Coast region. In turn, this has led to a reduction in air 

pollution transported to San Diego. 

Substantial emission reductions occurring in San Diego County coupled with a reduction in 

transported air pollution from South Coast provided for attainment of the former one-hour ozone 

NAAQS in San Diego County. Similarly, as previously illustrated in Figure 1-4, substantial 

progress has already been achieved in San Diego toward attaining the more stringent eight-hour 

ozone NAAQS. Nevertheless, transported air pollution will continue to play a substantial role in 

the region’s ability to expeditiously attain and maintain the ozone NAAQS. 

1.5 ATTAINMENT PLANNING REQUIREMENTS 

EPA promulgated Phase 1 of its eight-hour ozone implementation rule in April 2004, establishing 

the nonattainment classification scheme and attainment dates for nonattainment areas.12 EPA 

followed up its Phase 1 ozone implementation rule with a final (Phase 2) rule in November 2005, 

 

11 The South Coast Air Basin includes Orange County and the metropolitan portions of Los Angeles, Riverside, and 

San Bernardino Counties. 

12 69 FR 23951. 

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1.0 Introduction and Overview

specifying the planning and emission control requirements regions must address in their 

implementation plans.13 

Pursuant to EPA’s Phase 1 eight-hour ozone implementation rule, all Basic Nonattainment Areas—

including San Diego County—are subject to the general planning and emission control 

requirements of Subpart 1 (of Part D of Title I) of the CAA. These Subpart 1 requirements are 

discussed in detail in Section 1.5.2 below. Basic Nonattainment Areas are not subject to the 

additional, more prescriptive requirements of Subpart 2, which were originally established for the 

former one-hour ozone NAAQS. 

1.5.1 2006 Appeals Court Decision and Implications

Several parties have filed lawsuits challenging various elements of EPA’s ozone implementation 

rules. During development of this Attainment Plan, a federal Appeals Court vacated (voided) 

EPA’s Phase 1 ozone implementation rule.14 The Appeals Court disagreed with EPA applying 

Subpart 1 to all eight-hour ozone nonattainment areas that have attained the former one-hour ozone 

NAAQS, and indicated that some such areas (possibly including San Diego County) must also be 

subject to Subpart 2 requirements. The Appeals Court remanded the matter back to EPA. 

However, the Department of Justice (on behalf of EPA) and other parties have appealed the 

Decision. 

Implications. The Appeals Court Decision calls into question whether San Diego County will 

remain a Subpart 1/Basic Nonattainment Area or be classified in the future under Subpart 2. 

Regardless, most of the stringent Subpart 2 emission control requirements are already met in San 

Diego County pursuant to backsliding prohibitions for the former one-hour ozone NAAQS. These 

requirements, plus additional Subpart 2 requirements that would possibly apply, are discussed in 

Section 1.5.3. 

Resolution of the legal issues associated with EPA’s ozone implementation rules will take many 

months, if not years. In the meantime, the District is proceeding with this Eight-Hour Ozone 

Attainment Plan to ensure compliance with the June 15, 2007, submittal deadline (which was not 

vacated by the Appeals Court) and continued ozone air quality improvement in the San Diego 

region. However, additional or revised ozone planning efforts may be required in the future upon 

resolution of the legal issues associated with EPA’s ozone implementation rules. 

1.5.2 Subpart 1/Basic Nonattainment Area Requirements

Subpart 1, Basic Nonattainment Area requirements are fully addressed in this Attainment Plan, 

pursuant to CAA Section 172 and EPA’s previously issued Phase 1 and Phase 2 ozone 

implementation rules. Major requirements are summarized below. 

An Emission Inventory (Section 2.0) is a comprehensive tabulation of pollutants emitted into the 

air as a result of various activities, organized by emission source category. This Eight-Hour Ozone 

Attainment Plan includes updated inventories of ozone precursor emissions, VOC and NOx, for the 

 

13 70 FR 71612. 

14 U.S. Court of Appeals for the District of Columbia Circuit, Case No. 04-1200, South Coast Air Quality Management 

District v. Environmental Protection Agency; decided December 22, 2006. 

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1.0 Introduction and Overview

2002 base year (the year from which future-year inventories are projected)15 and the 2008 

attainment year, representative of a typical summer weekday. Section 2.0 also identifies Emission 

Budgets for transportation and general conformity purposes. 

The Emission Control Strategy (Section 3.0) identifies a comprehensive group of stationary and 

mobile source control measures to lead the region into eight-hour ozone attainment as expeditiously 

as practicable. The Emission Control Strategy provides for a demonstration of attainment within 

five years (June 15, 2009) of the nonattainment designation (June 15, 2004). Therefore, pursuant to 

EPA’s Phase 2 implementation rule, Basic Nonattainment Area requirements for Reasonably 

Available Control Technology (RACT) are fulfilled by the control measures relied on in the 

Attainment Demonstration.16 Similarly, the requirement for Reasonable Further Progress (RFP) is 

fulfilled because all necessary emission reductions will be achieved by the beginning of the 2008 

attainment year.17 Therefore, no separate discussions are needed in this Eight-Hour Ozone 

Attainment Plan to address RACT and RFP requirements. However, additional RACT and RFP 

requirements would apply if the region is subsequently classified as a Subpart 2 Nonattainment 

Area under any rule revisions EPA may be required to issue responding to the court order (see 

Section 1.5.3). 

An analysis of Reasonably Available Control Measures (RACM, Section 3.4) is presented 

pursuant to federal requirements to determine whether additional technologically and economically 

feasible control measures could advance the ozone attainment date by one or more years. The 

stringency and comprehensiveness of currently adopted control requirements on emission sources in 

San Diego County significantly reduces the availability of potential new measures that could 

provide additional emission reductions to advance the attainment year. The RACM analysis 

demonstrates there are no additional economically and technologically feasible control measures 

(alone or in conjunction with others) that could advance the attainment year from 2008 to 2007. 

An Attainment Demonstration (Section 4.0) was developed pursuant to federal requirements, 

using photochemical air quality simulation modeling and other approved analytical techniques 

(collectively called “Weight of Evidence”) to demonstrate the ability of the Emission Control 

Strategy (Section 3.0) to provide for eight-hour ozone attainment as expeditiously as practicable. 

Ozone nonattainment areas are required to model attainment in the ozone season18 prior to the 

area’s attainment date.19 For San Diego County, the demonstrated “attainment year” is 2008, 

representing the first full ozone season prior to the June 15, 2009, attainment date. 

Contingency Measures (Section 5.0) are required, pursuant to CAA Section 172(c)(9), to be 

implemented in the event of failure to achieve RFP milestones or failure to attain the NAAQS by 

 

15 EPA established 2002 as the emission inventory base year for eight-hour ozone planning purposes. See “2002 Base 

Year Emission Inventory SIP Planning: 8-hr Ozone, PM2.5 and Regional Haze Programs,” Lydia Wegman, Director, 

Air Quality Standards and Strategy Division, November 18, 2002 

(www.epa.gov/ttnchie1/eidocs/2002baseinven_102502new.pdf). 

16 40 CFR 51.912(c)(1). 

17 40 CFR 51.910(b)(2)(i). 

18 San Diego’s ozone season (when eight-hour ozone exceedances can be expected) has long been specified in federal 

regulation (40 CFR Part 58, Appendix D, section 2.5) as January through December. However, based on eight-hour 

ozone levels in recent years, the region’s ozone season is more likely May through September (see Section 4.4.5). 

Regardless, for purposes herein, the full ozone season remains January through December. 

19 40 CFR 51.908(d). 

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1.0 Introduction and Overview

the attainment deadline. The Contingency Measures requirement is intended to ensure emission 

reduction progress continues while the failure is being corrected. 

Typically, contingency measures are held in reserve and implemented only if required. However, 

California's stringent emissions control program and on-going emissions reduction trend create a 

unique situation, allowing this Attainment Plan to identify several mobile source control regulations 

as contingency measures that will be implemented regardless of contingency measure requirements. 

These measures provide additional emission reductions, beyond those relied on in the Attainment 

Demonstration. 

New Source Review (NSR) rules are required by the CAA. For purposes of implementing the 

eight-hour ozone NAAQS, the NSR rules must have applicability thresholds and offset ratios at 

least as stringent as mandated in the CAA for the nonattainment area’s classification. Since San 

Diego County was designated under Subpart 1 as a Basic Nonattainment Area, the mandated 

applicability threshold for VOC and NOx emissions is 100 tons per year, and the mandated offset 

ratio is at least 1-to-1. If in the future the area were classified Moderate under Subpart 2 (see 

Section 1.5.3), the same 100 tons per year threshold would apply, but the mandated offset ratio 

would be 1.15-to-1. 

The District’s current NSR rules (Rules 20.1 – 20.4) were adopted in 1998 when San Diego County 

was classified as a Serious Nonattainment Area for the one-hour ozone NAAQS, but they have not 

yet been approved into the SIP. The offset applicability threshold in the current NSR rules is 50 

tons per year and the offset ratio is 1.2-to-1. In the District’s EPA-approved NSR rules (adopted in 

1979) that are included in the federally enforceable SIP, the offset applicability threshold is 100 

tons per year and the offset ratio is 1.2-to-1. The District’s NSR rules (both versions) also require 

Lowest Achievable Control Technology and other requirements mandated for nonattainment areas. 

Thus, both versions of the District’s NSR rules fulfill the eight-hour ozone requirements, whether 

San Diego County remains under Subpart 1 or is classified Moderate under Subpart 2. 

1.5.3 Subpart 2/Moderate Nonattainment Area Requirements

Current Subpart 2 requirements are also addressed in this Attainment Plan, in the event the region 

would be classified as a Subpart 2 nonattainment area under an EPA rule revision. Based on the 

region’s 2003 eight-hour ozone design value (0.093 ppm), Moderate Nonattainment Area 

requirements would likely apply under this scenario. 

Importantly, Subpart 2 requirements have long been implemented in San Diego County pursuant to 

the region’s former status as Subpart 2/Serious Nonattainment Area for the one-hour ozone 

NAAQS.20 These requirements continue to be implemented in the region and are required under 

federal anti-backsliding provisions, and include the following: 

1. Enhanced vehicle inspection and maintenance program [CAA Section 182(c)(3)]; 

2. Stage II gasoline vapor recovery [CAA Section 182(b)(3)]; 

 

20 Subpart 2/Serious Nonattainment provisions were fully satisfied in San Diego County pursuant to the 1994 OneHour Ozone Attainment Plan, approved by EPA (62 FR 1150). Compliance with Subpart 2 was reaffirmed by EPA 

when redesignating the region to a Maintenance Area for one-hour ozone (68 FR 13653). 

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1.0 Introduction and Overview

3. Reformulated gasoline [CAA Section 211(k)]; 

4. New Source Review regulations for new or modified major stationary sources of VOC or 

NOX, including an offset ratio of 1.2:1 [CAA Section 182(c)(10)]; 

5. Reasonably Available Control Technology for existing major stationary sources of NOx 

[CAA Section 182(f)]; 

6. Periodic emissions inventory and source emission statement regulations [CAA Section 

182(a)(3)]; and 

7. Enhanced ambient monitoring [Photochemical Assessment Monitoring Stations (PAMS), 

CAA Section 182(c)(1)]. 

Limited Further Requirements Under Subpart 2. If in the future San Diego County were to be 

classified by EPA as a Subpart 2/Moderate Nonattainment Area, at least two additional SIP 

submittal requirements could apply in addition to those already implemented in the region. 

1. Reasonably Available Control Technology [CAA Section 182(b)(2)]: In a separate SIP 

submittal, a Subpart 2 region must newly reevaluate and assure RACT requirements are met 

for each applicable category of stationary sources of VOC and NOx.21 

2. Reasonable Further Progress [CAA Section 182(c)(2)(b)]: Newly classified Moderate areas 

may be required to submit new RFP demonstrations. 

These detailed RACT and RFP requirements do not apply to this Attainment Plan because it is 

prepared pursuant to Subpart 1 requirements. If EPA subsequently classifies San Diego County 

under Subpart 2, then reasonable deadlines for compliance with additional requirements will be 

specified by EPA. 

1.5.4 Attainment Finding Versus Attainment Demonstration

The Attainment Demonstration required to be included in this Attainment Plan differs from an 

“attainment finding” that EPA must issue after an area has actually attained the NAAQS. This 

Attainment Demonstration is a prediction of clean air quality in the forecasted attainment year 

(2008). An attainment finding is an after-the-fact determination that the NAAQS has been attained. 

An actual attainment finding must be based on three consecutive years of ambient ozone monitoring 

data. An actual attainment finding in 2008 for San Diego County, based on the 2006-2008 

three-year period, is not anticipated due to higher eight-hour ozone levels that occurred during a 

record-breaking heat wave in 2006.22. Nevertheless, pursuant to federal requirements, an 

 

21 RACT compliance options for Subpart 2 areas include (1) certifying that ongoing RACT rules for one-hour ozone 

implementation represent RACT for eight-hour ozone purposes; or (2) making a new RACT determination and any 

associated rule revisions. 

22 See Attachment G for a discussion of unusual meteorological conditions in 2006 that led to higher eight-hour ozone 

levels. 

Eight-Hour Ozone Attainment Plan Page 1-11
1.0 Introduction and Overview

Attainment Demonstration for 2008 is not required to present three years of ambient ozone data 

(2006–2008) that provide for attainment in the attainment year (2008).23 Rather, areas must 

demonstrate that the attainment year itself (2008) is anticipated to be a “clean” year with respect to 

eight-hour ozone levels, with a prediction of three or fewer exceedances of the NAAQS at each 

monitor in that year.24 

The air quality simulation modeling runs predict 2008 ozone concentrations of 0.086 ppm, just 

slightly higher than the 0.085 ppm level representing the standard. However, statistical air quality 

trends analyses included in the Weight of Evidence demonstration indicate that historical eight-hour 

ozone design values at the Alpine monitoring site have been decreasing at a rate that would lead to 

attainment years ranging from 2006 to 2008. Thus, the Weight of Evidence predicts 2008 to be a 

clean year. 

If, as predicted, 2008 proves to be a “clean year” for eight-hour ozone levels in San Diego County 

(as occurred in 2004, with just two exceedances measured at Alpine), then the region will qualify 

for a one-year attainment date extension provided under CAA Section 172(a)(2)(C), extending the 

three-year attainment period to 2007-2009. Further, if high ozone concentrations were to occur in 

2007 that prevent actual attainment in the 2007-2009 timeframe, but 2009 itself is a “clean year,” 

then a second one-year extension would be available, and attainment must then be achieved based 

on the 2008-2010 three-year period. Thus, a “2008 attainment demonstration” corresponds to a 

forecast of clean years in 2008 and 2009 and actual attainment based on either the 2007-2009 or 

2008-2010 three-year period. 

 

23 66 FR 57163; 71 FR 52678-79. 

24 The Attainment Demonstration’s focus on a single attainment year, rather than on a three-year attainment period, is 

consistent with federal requirements to achieve all necessary emission reductions by the beginning of the attainment 

year, not three years prior to the area’s attainment date. This approach is also a function of how the photochemical air 

quality simulation model operates, predicting air quality for one year. 

Eight-Hour Ozone Attainment Plan Page 1-12
2.0 Emission Inventories and Trends

2.0 EMISSION INVENTORIES AND TRENDS 

2.1 INVENTORY DEVELOPMENT PROCESS 

Emission inventories, projections, and trends in this Eight-Hour Ozone Attainment Plan are based 

on the latest Ozone SIP Planning Emission Projections compiled and maintained by ARB.1 

Supporting data were developed jointly by stakeholder agencies, including ARB, the District, 

SCAQMD, the Southern California Association of Governments (SCAG), and the San Diego 

Association of Governments (SANDAG). Each agency plays a role in collecting and reviewing 

data as necessary to generate comprehensive emission inventories. The supporting data include 

socio-economic projections, industrial and travel activity levels, emission factors, and emission 

speciation profiles. 

ARB compiles annual statewide emission inventories in its emission-related information database, 

the California Emission Inventory Development and Reporting System (CEIDARS). Emission 

projections for past and future years were generated using the California Emission Forecasting 

System (CEFS), developed by ARB to project emission trends and track progress towards meeting 

emission reduction goals and mandates. CEFS utilizes the most current growth and emissions 

control data available and agreed upon by the stakeholder agencies to provide comprehensive 

projections of anthropogenic (human activity-related) emissions for any year from 1975 through 

2030. 

Local air districts are responsible for compiling emissions data for all point sources and many 

stationary area-wide sources. For mobile sources, CEFS integrates emission estimates from ARB’s 

EMFAC2007 and OFFROAD models. SCAG and SANDAG incorporate data regarding highway 

and transit projects into their Travel Demand Models for estimating and projecting vehicle miles 

traveled (VMT) and speed. ARB’s on-road emissions inventory in EMFAC2007 relies on these 

VMT and speed estimates. To complete the inventory, estimates of biogenic (naturally occurring) 

emissions are developed by ARB using the Biogenic Emissions Inventory Geographic Information 

System (BEIGIS) model. 

2.2 INVENTORIES FOR 2002 BASE YEAR AND 2008 ATTAINMENT YEAR 

Detailed inventories (by source category) of ozone-precursor emissions (VOC and NOx) for the 

2002 base year and 2008 attainment year are presented in Attachment A and illustrated in 

Figure 2-1. Because San Diego’s ozone air quality is often affected by emissions from the South 

Coast Air Basin (see Section 1.4.2), both an inventory of San Diego-only emissions and an 

inventory of combined San Diego plus South Coast emissions are presented. The latter scenario is a 

general indicator of progress for the South Coast-San Diego transport couple. 

 

1 Version 1.06 Rf#980. 

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2.0 Emission Inventories and Trends

FIGURE 2-1 

Ozone Precursors Emissions in San Diego County 

and South Coast Air Basin 

0

200

400

600

800

1000

1200

1400

2002

SD

VOC

2008

SD

VOC

2002

SD 

NOx

2008

SD 

NOx

2002

SD+SC

VOC

2008

SD+SC

VOC

2002

SD+SC

NOx

2008

SD+SC

NOx

tons per day

Offroad

Onroad

Areawide

Stationary

SD = San Diego Air Basin; SC = South Coast Air Basin 

Source: ARB SIP emissions inventory. 

2.3 LONG-TERM EMISSION TRENDS 

Projected emission reduction trends in San Diego County for VOC and NOx are illustrated in 

Figures 2-2 and 2-3, respectively. A 30-year time period, looking back to 1990 and forward to 

2020, is presented. Only currently adopted emission control regulations are reflected in future year 

projections. The resulting data are disaggregated for onroad, offroad, areawide, and stationary 

source emissions. 

As new lower-emitting motor vehicles (required by State regulations) gradually replace used, 

higher-emitting vehicles, the share of VOC and NOx emissions from motor vehicles is projected to 

drop. Stationary source control measures continue to hold stationary source emissions relatively 

constant despite economic growth. Nevertheless, although not reflected in the figures, future 

ongoing implementation of the every-feasible-control-measure requirement of State law will likely 

provide further reductions in emissions as additional cost-effective control technologies become 

available. 

Eight-Hour Ozone Attainment Plan Page 2-2 
2.0 Emission Inventories and Trends

FIGURE 2-2 

Volatile Organic Compounds Emissions Trend in San Diego County 

0

50

100

150

200

250

300

350

400

1990199119921993199419951996199719981999200020012002200320042005200620072008200920102011201220132014201520162017201820192020

tons per day

Offroad

Onroad

Areawide

Stationary

Source: ARB SIP emissions inventory. 

FIGURE 2-3 

Oxides of Nitrogen Emissions Trend in San Diego County 

0

50

100

150

200

250

300

350

1990199119921993199419951996199719981999200020012002200320042005200620072008200920102011201220132014201520162017201820192020

tons per day

Offroad

Onroad

Areawide

Stationary

Source: ARB SIP emissions inventory. 

Eight-Hour Ozone Attainment Plan Page 2-3 
2.0 Emission Inventories and Trends

2.4 EMISSION BUDGETS 

2.4.1 On-Road Motor Vehicle Emission Budgets For Transportation Conformity

The federal transportation conformity regulation2 requires the Eight-Hour Ozone Attainment Plan 

to specify on-road motor vehicle emission budgets for the 2008 Attainment Year.3 The 2008 

Attainment Year emission budgets will also apply to all post-2008 future transportation conformity 

analysis years, as authorized in the federal transportation conformity rule.4

TABLE 2-3 

On-Road Motor Vehicle Emission Budgets in San Diego County 

For 2008 and Subsequent Years 

(tons per day) 

Pollutant 2008 and Subsequent Years 

VOC 53 

NOx 98 

Note: Emission budgets are based on ARB’s EMFAC2007 model 

with ARB off-model adjustments and reflect “summer day.” 

The emission budgets presented in Table 2-3 represent the on-road motor vehicle emission levels 

projected for 2008, as determined by ARB using ARB’s EMFAC2007 on-road motor vehicle 

emissions estimation model and adjusted by ARB to reflect recently adopted emission control 

programs not reflected in EMFAC2007 and other corrections. 

Minor budget adjustments were made to account for imprecision in the on-road motor vehicle 

emissions modeling process.5 The emission budgets are expressed as whole numbers, and therefore 

on-road motor vehicle emission estimates should be rounded to whole numbers (in tons per day) 

using standard rounding conventions (.49 rounds down; .50 rounds up) prior to being compared to 

emission budgets for transportation conformity determinations. 

 

2 40 CFR 93 (“Determining Conformity of Federal Actions to State or Federal Implementation Plans”). 

3 40 CFR 93.118 (“Criteria and Procedures: Motor Vehicle Emissions Budget”). 

4 40 CFR 93.118(b)(2). 

5 To establish the emission budgets, the 2008 on-road motor vehicle emissions estimates were adjusted by rounding up to the next

whole number (tons per day), and adding one. This same adjustment procedure was previously used in the approved One-Hour 

Ozone Maintenance Plan. 

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2.0 Emission Inventories and Trends

2.4.2 Military Growth Increment for General Conformity

The federal general conformity regulation6 and corresponding District Rule 15017 require federal 

agencies proposing major federal actions to make a determination that proposed actions will 

conform to the applicable SIP. Specifically, proposed federal actions may not cause or contribute to 

a NAAQS violation or interfere with the purposes of an applicable SIP. A method for 

demonstrating conformity is forecasting and accounting for reasonably anticipated emissions from 

future actions by federal agencies in the applicable SIP (attainment or maintenance plan).8

The Department of the Navy (DoN) previously developed, for inclusion in the One-Hour Ozone 

NAAQS Maintenance Plan (2002), a projection of future mobile source emissions from anticipated 

military actions that may occur during the twenty-year maintenance period.9 The NOx emission 

projections for the Maintenance Plan included a Military Growth Increment of 11.4 tons per day. 

The ongoing reduction in total regionwide NOx emissions outweighs projected growth in NOx 

emissions from military activity. Consequently, the Military Growth Increment of NOx emissions 

in the Maintenance Plan did not jeopardize ongoing maintenance of the one-hour ozone standard. 

Further, no growth is anticipated in mobile source VOC emissions from future military activities. 

Rather, VOC reductions from the proposed actions are anticipated. 

However, in recognition of the need for further reductions in ozone-precursor emissions to provide 

for expeditious attainment of the more stringent eight-hour ozone NAAQS, the District has 

reevaluated whether and what size of a military-growth NOx emissions increment can be 

accommodated in this Eight-Hour Ozone Attainment Plan. DoN has requested a reduced increment 

of 2.3 tons per day of NOx emissions (see Attachment B) be included in this Attainment Plan to 

account for those projects that DoN has planned for implementation during the period in which this 

Attainment Plan is the applicable SIP (prior to attainment and subsequent replacement of this SIP 

by a new maintenance plan). The 2.3 tons per day of NOx emissions would result from plans to 

replace older aircraft at Miramar and Camp Pendleton with new advanced-technology aircraft that 

produce higher NOx emissions but lower VOC emissions, as well as plans for home-porting a new 

shallow-water combat ship at Naval Station San Diego. For perspective, military aircraft and ship 

activities over and offshore of San Diego County currently emit approximately 10 tons per day of 

NOx. 

Attachment B presents preliminary schedules for implementation of the planned military projects 

through 2015. For purposes of analyzing the potential impact of these projects on 2008 ozone 

attainment, total emissions from full implementation of these projects were assumed to occur in 

2008. The analysis indicates that the emissions growth allowance requested by the military can be 

accommodated without jeopardizing the demonstration of eight-hour ozone attainment by the 2008 

deadline.10 Consequently, a growth allowance of 2.3 tons per day of NOx emissions is incorporated 

in this Eight-Hour Ozone Attainment Plan. 

 

6 40 CFR 51, subpart W (“Determining Conformity of General Federal Actions to State or Federal Implementation Plans). 

7 APCD Rule 1501, “Conformity of General Federal Actions,” fully approved by EPA on April 23, 1999 (64 FR 19916). 

8 40 CFR 51.858(a)(1). 

9 “Navy/Marine Corps Mobile Source Emissions Growth Projection and SIP Planning,” Department of the Navy, San Diego County, California, June 

6, 2002. 

10 Comparison of modeling 2008 with and without the planned military projects indicates the combination of NOx emission increases and VOC 

decreases associated with the projects would result in slightly lower ozone concentrations by a small fraction of a part per billion. 

Eight-Hour Ozone Attainment Plan Page 2-5 
2.0 Emission Inventories and Trends

2.5 PRE-BASELINE BANKED EMISSION CREDITS 

The District’s federally mandated New Source Review Rules require new and modified major 

stationary sources that increase emissions in amounts exceeding specified thresholds to provide 

emission reduction offsets to mitigate the emissions growth. Emission reduction offsets represent 

either on-site emission reductions or the use of banked emission reduction credits (ERCs), which 

are voluntary, surplus emission reductions previously achieved and registered with the District for 

future use as offsets. As a result of offset requirements, there should be no net effect on emission 

inventories from future construction or modification of major sources; in other words, associated 

emission increases that otherwise would be added to the inventory are effectively canceled out by 

reductions of other emissions that are in the inventory. The “no net effect on the inventory” result 

from new or modified major sources holds true only if the emissions that are reduced to provide 

offsets remain in the inventory. 

To ensure construction or modification of major sources has no net effect on emission inventories 

used for demonstrating eight-hour ozone attainment, banked ERCs derived from pre-2002 emission 

reductions—which otherwise would not be included as emissions in the baseline and subsequent 

inventories—must be added back into the inventories as if these emission were still in the air, 

pursuant to federal requirements.11 Accordingly, Attachment C presents the pre-baseline ERCs 

currently in the District’s credit bank that have been added to the 2008 Attainment Year Emissions 

Inventory. 

 

11 FR 70 71676. 

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3.0 Emission Control Strategy

3.0 EMISSION CONTROL STRATEGY 

3.1. SUMMARY 

Over the past two decades, ozone air quality in San Diego County has improved significantly (see 

Sections 1.4 and 4.4) due to comprehensive control strategies implemented to reduce pollution from 

mobile and stationary emission sources. Those controls were primarily designed to address the 

former one-hour ozone NAAQS. However, ongoing controls and reductions in peak ozone levels 

have also substantially reduced eight-hour average ozone such that the region is now close to 

attaining the eight-hour ozone NAAQS. Further, existing District, State, and federal regulations 

will provide additional reductions in ozone precursors for the foreseeable future (see Sections 2.3 

and 4.4.4 for emission trends). Given the success of the existing comprehensive regulatory 

program, the Emission Control Strategy for this Eight-Hour Ozone Attainment Plan relies primarily 

on ongoing implementation of existing District, State, and federal regulations to attain the eighthour ozone NAAQS as expeditiously as practicable. These currently adopted regulations are 

referred to as the “Existing Control Strategy,” which is described in Section 3.2 

This Attainment Plan also reflects two additional stationary source control rules being submitted 

into the SIP, collectively providing an estimated 2.4 tons per day of VOC reduction between 2002 

and 2008. First, the newest version of Rule 67.0 (Architectural Coatings) is being submitted into 

the SIP along with this Attainment Plan (see Section 3.2.2). Second, a new additional control 

measure (Low VOC Solvent Cleaning) is planned to be implemented in 2008 (see Section 3.3). 

3.2 EXISTING CONTROL STRATEGY 

3.2.1 State and Federal Control Programs

The California ARB is responsible for controlling emissions from mobile sources (except where 

federal law preempts ARB’s authority) and consumer products, developing fuel specifications, 

adopting statewide control measures for air toxics, and establishing gasoline vapor recovery 

standards and certifying vapor recovery systems. ARB has regulated mobile sources since the 

1960s and consumer products since the early 1990s, and has added to and significantly tightened 

those regulations many times over the years. 

The State Department of Pesticide Regulation (DPR) is responsible for control of agricultural, 

commercial and structural pesticides. The State Bureau of Automotive Repair (BAR) runs the 

State’s Smog Check programs to identify and repair higher polluting cars. 

EPA is authorized to control emissions from mobile sources, including sources under exclusive 

federal jurisdiction (such as interstate trucks, some farm and construction equipment, locomotives, 

aircraft, and marine vessels based in the U.S.). International organizations develop standards for 

aircraft and marine vessels that operate outside the U.S. Federal agencies have the lead role in 

representing the U.S. in the process of developing international standards. 

Control measures implemented by State and federal agencies pursuant to California’s 1994 Ozone 

SIP (addressing the former one-hour ozone NAAQS) are presented in Table 3-1. In 2003, ARB 

Eight-Hour Ozone Attainment Plan Page 3-1 
3.0 Emission Control Strategy

identified another series of new statewide mobile and area source control measures to achieve 

further progress in ozone air quality. These measures are listed in Table 3-2. 

The existing State and federal emission control regulations will continue providing significant 

emission reductions through the coming decade as the regulations are fully implemented. From 

2002 to 2008, these regulations will reduce daily ozone precursor emissions in San Diego County 

by more than 70 tons, as presented in Table 3-3. 

TABLE 3-1 

State and Federal Control Measures Adopted Since 1994 Ozone SIP 

Responsible 

Agency Adopted 

Defined Measures in 1994 Ozone SIP

M1: Light-duty vehicle scrappage ARB 1998 

M2: Low Emission Vehicle II program ARB 1998 

M3: Medium-duty vehicles ARB 1995 

M4: Incentives for clean engines (Moyer Program) ARB 1999 

M5: California heavy-duty diesel vehicle standards ARB 1998 

M6: National heavy-duty diesel vehicle standards U.S. EPA 1998 

M7: Heavy-duty vehicle scrappage ARB Replaced with M17

M17: In-use reductions from heavy-duty vehicles ARB No 

M8: Heavy-duty gasoline vehicle standards ARB 1995 

M9: CA heavy-duty off-road diesel engine standards ARB 2000 

M10: National heavy-duty off-road diesel engine stds U.S. EPA 1998 

M11: CA large off-road gas/LPG engine standards ARB 1998 

M12: National large off-road gas/LPG engine stds U.S. EPA 2002 

M13: Marine vessel standards U.S. EPA 1999 

M14: Locomotive engine standards U.S. EPA 1997 

M15: Aircraft standards U.S. EPA No 

M16: Marine pleasurecraft standards U.S. EPA 1996 

CP2: Consumer products mid-term measures ARB 1997/1999 

CP3: Aerosol paint standards ARB 1995/1998 

Enhanced I/M (Smog Check II) BAR 1995 

DPR-1: Emission reductions from pesticides DPR Voluntary 

Adopted measures not originally included in 1994 Ozone SIP

Clean fuels measures ARB Multiple 

Marine pleasurecraft (reductions beyond M16) ARB 1998/2001 

Motorcycle standards ARB 1998 

Urban transit buses ARB 2000 

Enhanced vapor recovery program ARB 2000 

Medium/heavy-duty gasoline standards (beyond M8) ARB 2000 

2007 heavy-duty diesel truck standards (beyond M5 and M6) ARB/U.S. EPA 2001 

Small off-road engine standard revisions ARB 1998 

Source: “2003 State and Federal Strategy for the California State Implementation Plan,” ARB, September 2003. 

Eight-Hour Ozone Attainment Plan Page 3-2 
3.0 Emission Control Strategy

TABLE 3-2 

State Measures Identified in the 2003 Ozone SIP 

Strategy 

(Agency) Name Adoption 

Years 

Implementation 

Years 

LT/MEDDUTY-1 

(ARB) 

Replace or Upgrade Emission Control 

Systems on Existing Passenger Vehicles – 

Pilot Program 

2005 2007-2008 

LT/MEDDUTY-2 

(BAR) 

Improve Smog Check to Reduce Emissions 

from Existing Passenger and Cargo Vehicles 2002-2005 2002-2006 

ON-RD 

HVY-DUTY1 

(ARB) 

Augment Truck and Bus Highway 

Inspections with Community-Based 

Inspections 

2003 2005 

ON-RD 

HVY-DUTY2 

(ARB) 

Capture and Control Vapors from Gasoline 

Cargo Tankers 2005 2006-2007 

ON-RD 

HVY-DUTY3 

(ARB) 

Pursue Approaches to Clean Up the Existing 

and New Truck/Bus Fleet 2003-2006 2004-2010 

OFF-RD CI-1 

(ARB) 

Pursue Approaches to Clean Up the Existing 

Heavy-Duty Off-Road Equipment Fleet 

(Compression Ignition Engines) – Retrofit 

Controls 

2004-2008 2006-2010 

OFF-RD CI-2 

(ARB) 

Implement Registration and Inspection 

Program for Existing Heavy-Duty Off-Road 

Equipment to Detect Excess Emissions 

(Compression Ignition Engines) 

2006-2009 2010 

OFF-RD 

LSI-1 

(ARB) 

Set Lower Emission Standards for New OffRoad Gas Engines (Spark Ignited Engines 

25 hp and Greater) 

2004-2005 2007 

OFF-RD 

LSI-2 

(ARB) 

Clean Up Off-Road Gas Equipment Through 

Retrofit Controls and New Emission 

Standards (Spark-Ignition Engines 25 hp and 

Greater) 

2004 2006-2012 

SMALL 

OFF-RD-1 

(ARB) 

Set Lower Emission Standards for New 

Handheld Small Engines and Equipment 

(Spark Ignited Engines Under 25 hp such as 

Weed Trimmers, Leaf Blowers, and 

Chainsaws) 

2003 2005 

SMALL 

OFF-RD-2 

(ARB) 

Set Lower Emission Standards for New NonHandheld Small Engines and Equipment 

(Spark Ignited Engines Under 25 hp such as 

Lawnmowers) 

2003 2007 

MARINE-1 

(ARB) 

Pursue Approaches to Clean Up the Existing 

Harbor Craft Fleet – Cleaner Engines and 

Fuels 

2003-2005 2005 

MARINE-2 

(ARB) 

Pursue Approaches to Reduce Land-Based 

Port Emissions – Alternative Fuels, Cleaner 

Engines, Retrofit Controls, Electrification, 

Education Programs, Operational Controls 

2003-2005 2003-2010 

Eight-Hour Ozone Attainment Plan Page 3-3 
3.0 Emission Control Strategy

Strategy 

(Agency) Name Adoption Years 

Implementation 

Years 

FUEL-1 

(ARB) 

Set Additives Standards for Diesel Fuel to 

Control Engine Deposits 2006-2009 2006-2010 

FUEL-2 

(ARB) 

Set Low-Sulfur Standards for Diesel Fuel for 

Trucks/Buses, Off-Road Equipment, and 

Stationary Engines 

2003 2006 

CONS-1 

(ARB) Set New Consumer Products Limits for 2006 2003-2004 2006 

CONS-2 

(ARB) 

Set New Consumer Products Limits for 

2008-2010 2006-2008 2008-2010 

FVR-1 

(ARB) 

Increase Recovery of Fuel Vapors from 

Aboveground Storage Tanks 2003 2007 

FVR-2 

(ARB) 

Recover Fuel Vapors from Gasoline 

Dispensing at Marinas 2006-2009 2006-2010 

FVR-3 

(ARB) 

Reduce Fuel Permeation Through Gasoline 

Dispenser Hoses 2004 2007 

PEST-1 

(DPR) Implement Existing Pesticide Strategy --- 1996-2010 

Potential Range for Defined Near-Term State Measures 

Minimum Commitment via Adoption 2003-2006 

LONG-TERM 

STRATEGY 

(ARB) 

Lead Multi-Agency Effort (State, federal and 

local) and Public Process Beginning in 2004 

to Identify and Adopt Long-Term Measures 

2007-2009 2010 

Source: “2003 State and Federal Strategy for the California State Implementation Plan,” ARB, Sept 2003. 

TABLE 3-3 

2002-2008 San Diego County Emissions Reductions from 

Existing State and Federal Control Programs 

(tons per day) 

Source Category VOC Reductions NOx Reductions 

Consumer Products 2 -- 

Onroad Motor Vehicles 26 28 

Commercial Boats <1 2 

Recreational Boats 1 0 

Res/Ind/Const Equipment 2 7 

Farm Equipment <1 1 

Gasoline Cans 2 -- 

Pesticides <1 -- 

TOTAL 34 38 

Source: ARB SIP emissions inventory, Version 1.06. 

Eight-Hour Ozone Attainment Plan Page 3-4 
3.0 Emission Control Strategy

3.2.2 Local Control Measures

The District is primarily responsible for controlling emissions from stationary and areawide sources 

(with the exception of consumer products and pesticides) through rules and permitting programs. 

Examples of stationary and areawide sources include industrial sources such as factories, power 

plants, and chemical plants; commercial sources such as gas stations, dry cleaners, and paint spray 

booth operations; and residential sources such as water heaters, furnaces, and house paints. The 

District implements these control measures through adoption of rules, permits, inspections and 

testing of a wide variety of stationary sources. In addition, local transportation agencies are 

responsible for developing and implementing transportation control measures aimed at reducing 

vehicle activity and associated emissions. 

Existing District Rules. The District has already adopted rules to control almost all stationary 

source categories in San Diego County, as presented in Table 3-4 for NOx rules and Table 3-5 for 

VOC rules. Most of these rules were fully implemented and achieved their emission reductions 

before the 2002 base year for this Eight-Hour Ozone Attainment Plan. Enforcement of these rules 

continues, but they can not be considered as “control measures” for this Attainment Plan because 

they will not provide new additional emission reductions.1 

TABLE 3-4 

Existing District Rules to Control NOx Emissions 

Rule

Number Title

SIP 

Approval 

Date 

68 Fuel-Burning Equipment-Oxides of Nitrogen 04/09/1996 

69 Electrical Generating Steam Boilers, Replacement Units and New Units Not In SIP* 

69.2 Industrial & Commercial Boilers Process Heaters & Steam Generators 02/09/1996 

69.3 Stationary Gas Turbine Engines 06/17/1997 

69.3.1 Stationary Gas Turbine Engines – Best Available Retrofit Control Technology Not In SIP* 

69.4 Stationary Reciprocating Internal Combustion Engines 01/04/2006 

69.4.1 Stationary Reciprocating Internal Combustion Engines– Best Available Retrofit Control 

Technology Not In SIP* 

69.5 Natural Gas-Fired Water Heaters Not In SIP* 

69.6 Natural Gas-Fired Fan-Type Central Furnaces Not In SIP* 

* The District has adopted and implemented additional rules pursuant to California’s stringent requirements for Best 

Available Retrofit Control Technology (BARCT). The District’s BARCT rules have not been submitted into the SIP 

because they are not required by federal law and are not credited as control measures in this Eight-Hour Ozone 

Attainment Plan. 

 

1 For purposes of this Emission Control Strategy section, the term “control measure” refers to new rules and regulations 

that are submitted into the SIP and provide new additional emission reductions (not previously accounted for) beyond 

the 2002 base year.

Eight-Hour Ozone Attainment Plan Page 3-5 
3.0 Emission Control Strategy

TABLE 3-5 

Existing District Rules to Control VOC Emissions 

Rule

Number Title

SIP 

Approval 

Date 

61.0 Definitions Pertaining to the Storage and Handling of Organic Compounds 09/13/1993 

61.1 Receiving and Storing Volatile Organic Compounds at Bulk Plants and Bulk Terminals 08/08/1995 

61.2 Transfer of Organic Compounds Into Mobile Transport Tanks 08/26/2003 

61.3 Transfer of Volatile Organic Compounds Into Stationary Storage Tanks 06/30/1993 

61.3.1 Transfer of Gasoline Into Stationary Underground Storage Tanks Not In SIP*

61.4 Transfer of Volatile Organic Compounds Into Vehicle Fuel Tanks 05/13/1993 

61.4.1 Transfer of Gasoline From Stationary Underground Storage Tanks Into Vehicle Fuel Tanks Not In SIP*

61.5 Visible Emission Standards for Vapor Control Systems 04/14/1981 

61.7 Spillage of Volatile Organic Compounds 03/11/1998 

61.8 Certification Requirements for Vapor Control Equipment 03/11/1998 

66 Organic Solvents 08/11/1998 

67.0 Architectural Coatings 03/27/1997 

67.1 Alternative Emission Control Plans 03/27/1997 

67.2 Dry Cleaning Equipment Using Petroleum-Based Solvent 03/27/1997 

67.3 Metal Parts and Products Coating Operations 11/14/2003 

67.4 Metal Container, Metal Closure and Metal Coil Coating Operations 11/03/1997 

67.5 Cutback and Emulsified Asphalt 03/27/1997 

67.6 Solvent Cleaning Operations 12/13/1994 

67.7 Cutback and Emulsified Asphalts 03/27/1997 

67.9 Aerospace Coating Operations 08/17/1998 

67.10 Kelp Processing and Bio-Polymer Manufacturing 06/22/1998 

67.11 Wood Products Coating Operations Not In SIP*

67.11.1 Large Wood Products Coating Operations 06/05/2003 

67.12 Polyester Resin Operations 03/27/1997 

67.15 Pharmaceutical & Cosmetic 03/27/1997 

67.16 Graphic Arts Operations 03/27/1997 

67.17 Storage of Materials Containing Volatile Compounds 03/27/1997 

67.18 Marine Coating Operations 03/27/1997 

67.19 Coatings and Printing Inks Manufacturing Operations 05/26/2000 

67.20 Motor Vehicle and Mobile Equipment Refinishing Operations Not In SIP*

67.21 Adhesive Materials Application Operations Not In SIP*

67.22 Expandable Polystyrene Foam Products Manufacturing Operations Not In SIP*

67.24 Bakery Ovens 03/27/1997 

* The District has adopted and implemented additional California BARCT rules that have not been submitted into the 

SIP because they are not required by federal law and are not credited as control measures in this Eight-Hour Ozone 

Attainment Plan. 

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Existing District Control Measure - Architectural Coatings. The District adopted the current 

version of Rule 67.0 (Architectural Coatings) in December 2001. It requires phased 

implementation of more stringent VOC content limits for certain coating categories that were 

implemented in 2003 and 2004. The rule provides an estimated 1.4 tons per day of additional VOC 

emission reductions. 

Since the recently implemented provisions of the Architectural Coatings Rule provided emission 

reductions after the 2002 baseline, the rule is considered a control measure for this Eight-Hour 

Ozone Attainment Plan. This version of the rule has not yet been submitted into the SIP. 

Consequently, it is being submitted into the SIP along with this Eight-Hour Ozone Attainment Plan.

3.3 ADDITIONAL NEW CONTROL MEASURE – LOW VOC SOLVENT CLEANING

The District is adopting a new control measure, as reflected in this Eight-Hour Ozone Attainment 

Plan, to reduce the VOC content of solvents used in cold solvent cleaning operations, effective in 

2008. The control measure will replace current District Rule 67.6 (Solvent Cleaning Operations) 

with two new rules, Rule 67.6.1 (Cold Solvent Cleaning and Stripping Operations) and Rule 67.6.2 

(Vapor Degreasing Operations), which are being adopted simultaneously with this Eight-Hour 

Ozone Attainment Plan. Proposed new Rule 67.6.1 will require that each solvent utilized in a cold 

solvent cleaning operation must have a VOC content of 50 grams per liter of material or less, in 

addition to other requirements. Proposed new Rule 67.6.2 will apply to vapor degreasing 

operations, with requirements that are generally identical to those in current Rule 67.6. 

When new Rule 67.6.1 is implemented in Spring 2008, San Diego County cold solvent cleaningrelated VOC emissions are projected to drop by approximately 1 ton per day relative to the 2002 

baseline. Because these emission reductions are not fully achieved before January 2008 (the 

beginning of the first full ozone season prior to the June 15, 2009, attainment deadline), they are not 

reflected in the Attainment Demonstration (Section 4.0), which shows attainment with the Existing 

Control Strategy. Nevertheless, the rule is identified as an additional control measure in this 

Attainment Plan to assist in reducing ozone concentrations in 2008 to below the level of the eighthour ozone NAAQS. 

3.4. REASONABLY AVAILABLE CONTROL MEASURES (RACM)

3.4.1. RACM Requirements

An analysis of Reasonably Available Control Measures (RACM) must demonstrate that the SIP 

provides for attainment as expeditiously as practicable.2 Demonstrating attainment as expeditiously 

as practicable is a two-step process. First, an initial control strategy is developed that can 

demonstrate attainment by the earliest year that is preliminarily considered to be feasible within the 

statutory maximum attainment deadline.3 The RACM analysis is then conducted as a second step, 

in which additional technologically and economically feasible potential control measures (that were 

not included in the initial control strategy) must be considered to determine if there is any 

 

2 CAA Section 172(c)(1). 

3 As a Subpart 1/Basic Nonattainment Area for eight-hour ozone, San Diego’s maximum attainment deadline is June 

15, 2009, plus up to five additional years, if necessary. 

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combination of additional control measures that could provide sufficient additional emission 

reductions in time to advance the attainment date by one or more years. The additional feasible 

control measures are determined to be “reasonably available” and must be included in the SIP only 

if implementing the measures can advance the attainment year. 

To be able to advance the attainment year, potential control measures must meet two pre-requisites. 

First, each control measure must be implemented in time to provide the intended emission 

reductions by the beginning of the ozone season of the earlier—i.e., advanced—attainment year. 

Second, the cumulative emission reduction potential (in that advanced attainment year) of all the 

candidate measures together would need to be sufficient to advance the attainment year. As 

discussed below, the stringency and comprehensiveness of the Existing Control Strategy, and the 

already early year forecast to reach attainment (2008), limits or eliminates the feasibility of 

additional measures that can satisfy these criteria. Specifically, such measures would have to 

advance attainment to 2007, the current year. 

3.4.2 Identifying Potential RACM for Stationary Sources

Identifying additional control measures for consideration as potential RACM is challenging in San 

Diego County because, in response to stringent requirements of State law, the District is already 

required to adopt every feasible control measure as expeditiously as practicable. Consequently, as 

previously presented in Table 3-4 for NOx and Table 3-5 for VOC, the District has already adopted 

rules to control almost all significant stationary source categories in the county. Most rules have 

been submitted into the SIP to fulfill federal requirements for Reasonably Available Control 

Technology (RACT). However, because California State law requires Best Available Retrofit 

Control Technology (BARCT) which is more stringent than RACT, the District has also adopted 

additional BARCT rules that have not been submitted into the SIP because they are not required by 

federal law or regulation. The District’s existing BARCT rules can not be considered as potential 

RACM because they have already been implemented and would not provide new additional 

emission reductions that could advance the attainment year. Nevertheless, those additional BARCT 

rules have already achieved emission reductions that contribute to the forecast of an early 

attainment year. 

The District has relied on an ongoing control measure evaluation process required under State law 

to identify potential RACM. Specifically, California local air districts must triennially update their 

air quality plans to achieve State ozone standards to include “every feasible control measure.” Each 

district is required to consider, for each emission source category, whether adopting some or all of 

the requirements of the most stringent adopted rule in the State for that source category would be 

feasible within that district. 

The District’s current review of the most stringent rules identified 17 source categories (listed in 

Table 3-6) for which the most stringent rules in the State contain more stringent requirements than 

San Diego APCD rules. Table 3-6 also indicates the implementation period, in years, that would be 

necessary to fully realize the emission reductions if the rules were locally adopted. The one- to 

three-year implementation periods indicated for the VOC control measures, and the two- to 25-year 

implementation periods for the NOx control measures, represent the time necessary to obtain lower 

emitting materials, install control equipment, or replace existing units at the end of their useful 

lives. Thus, even if all measures were adopted concurrent with this Attainment Plan in 2007 (which 

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3.0 Emission Control Strategy

is not feasible due to the lead time necessary for rule development and adoption), the reductions 

could not be fully realized before the beginning of 2007. Consequently, those measures are not 

available for advancing the attainment year to 2007. 

An analysis of each of the potential control measures identified in Table 3-6 is presented in 

Attachment D. 

TABLE 3-6 

Stationary Source Categories for Which More Stringent 

Control Requirements Have Been Adopted by Another District 

Control Measure 

Other 

District 

Rule 

Number* 

San Diego 

Rule Number 

Estimated 

Emission 

Reduction 

Potential 

(Tons/Day) 

Implementation 

Period (Years) Pollutant

Low VOC Solvent Cleaning SC 1122 67.6 1 1 VOC 

Architectural Coatings SC 1113 67.0 5 1 VOC 

Automotive Refinishing ARB SCM 67.20 1 2 VOC 

Adhesive and Sealant Applications SC 1168 67.21 1.4 1 VOC 

Solvent Wipe Cleaning Operations SC 1171 Various Rules 0.57 1 VOC 

Wood Products Coating Operations SC 1136 67.11-67.11.1 0.25 2 VOC 

Graphic Arts SC 1130 67.16 0.23 1 VOC 

High Emitting Spray Booth Facilities SC 1132 Various 

Coating Rules 0.15 2 VOC 

Petroleum Storage Tanks SC 1178 61.1 0.03 3 VOC 

Mobile Transport Tanks Loading SJV 4621 61.2 0.02 1 VOC 

Food Products Manufacturing/Processing SC 1131 No comparable 

rule 0.02 2 VOC 

Polyester Resins Operations SC 1162 67.12 0.02 1 VOC 

Equipment Leaks BA 8-18 Various Rules <0.02 1 VOC 

Aerospace Manufacturing Operations SC 1124 67.9 <0.01 1 VOC 

Industrial, Commercial, and Institutional 

Boilers SJV 4306 69.2 0.1 2 NOx 

Small Boilers and Large Commercial Water 

Heaters 

SC 1146.1 

& 1146.2 

No comparable 

rule 0.3 25** NOx 

Residential Water Heaters SC 1121 69.5 1.5 10** NOx 

*SC = South Coast air district; ARB = Air Resources Board; BA = Bay Area district; SJV = San Joaquin Valley district; 

SCM = Suggested Control Measure 

 **Emissions reductions would occur gradually, as new low-emitting units replace existing higher-emitting units at the end 

of their useful lives.

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3.4.3 Identifying Potential RACM for Transportation Sources

Potential RACM also include Transportation Control Measures (TCMs), which are strategies to 

reduce motor vehicle trips, vehicle miles traveled, or vehicle idling and associated air pollution. 

Table 3-7 lists the 16 TCMs identified in CAA Section 108(f) and their implementation status in 

San Diego County. A discussion of each TCM, further describing the status of implementation, 

follows Table 3-7. 

As indicated, 13 of the 16 TCMs have been implemented, including transit and traffic flow 

improvements, ridesharing, high occupancy vehicle (HOV) lanes, pedestrian-only streets, control of 

extended idling, and 7 other measures. The agencies responsible for developing and implementing 

these TCMs include the San Diego Association of Governments (SANDAG, the transportation 

planning agency for the San Diego region) and other State and local agencies as appropriate. 

Five of the implemented TCMs—TCMs 1, 3, 5, 8, and 10—were included in the 1982 SIP Revision 

for San Diego County.4 Descriptions herein of any ongoing implementation beyond 1982 SIP 

commitments does not constitute submittal of additional implementation commitments into the SIP. 

Submittal of additional TCM commitments into the SIP would be required only if the TCMs meet 

the RACM qualifications specified in Section 3.4.1. TCMs that have already been implemented can 

not provide new additional emissions reductions in 2007 that could advance the attainment year 

from 2008 to 2007. Therefore, they can not be considered RACM and consequently are not 

required to be submitted into the SIP. 

Table 3-7 and the subsequent discussion also address the three TCMs that have not been 

implemented in San Diego County and the reasons for non-implementation. These measures 

address trip-reduction ordinances, peak-period vehicle restrictions, and vehicle emissions in 

extremely cold environments. 

 

4 In the 1982 SIP, TCMs 3 and 8 (see Table 3-7) were combined into one comprehensive TCM, the “Ridesharing” 

TCM. 

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TABLE 3-7 

Transportation Control Measures listed in Clean Air Act Section 108(f) 

Implementation Status in San Diego County 

Transportation Control Measures Implemented In 1982 SIP 

1. Programs for improved public transit Yes Yes 

2. Restriction of certain roads or lanes to, or construction of such roads or lanes 

for use by, passenger buses or high occupancy vehicles Yes 

3. Employer-based transportation management plans, including incentives Yes Yes 

4. Trip-reduction ordinances 

 *Adopted in 1994, but rescinded in 1995 when federal and State laws were 

 amended eliminating the mandate for such measures

No* 

5. Traffic flow improvement programs that achieve emission reductions Yes Yes 

6. Fringe and transportation corridor parking facilities serving multiple 

occupancy vehicle programs or transit service Yes 

7. Programs to limit or restrict vehicle use in downtown areas or other areas of 

emission concentration particularly during periods of peak use No 

8. Programs for the provision of all forms of high-occupancy, shared-ride 

services Yes Yes 

9. Programs to limit portions of road surfaces or certain sections of the 

metropolitan area to the use of non-motorized vehicles or pedestrian use, 

both as to time and place 

Yes 

10. Programs for secure bicycle storage facilities and other facilities, including 

bicycle lanes, for the convenience and protection of bicyclists, in both public 

and private areas 

Yes Yes 

11. Programs to control extended idling of vehicles Yes 

12. Programs to reduce motor vehicle emissions, consistent with Title II, which 

are caused by extreme cold start conditions Not Applicable 

13. Employer-sponsored programs to permit flexible work schedules Yes 

14. Programs and ordinances to facilitate non-automobile travel, provision and 

utilization of mass transit, and to generally reduce the need for singleoccupant vehicle travel, as part of transportation planning and development 

efforts of a locality, including programs and ordinances applicable to new 

shopping centers, special events, and other centers of vehicle activity 

Yes 

15. Programs for new construction and major reconstructions of paths, tracks or 

areas solely for the use by pedestrian or other non-motorized means of 

transportation when economically feasible and in the public interest 

Yes 

16. Program to encourage the voluntary removal from use and the marketplace 

of pre-1980 model year light duty vehicles and pre-1980 model light duty 

trucks 

Yes 

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3.4.3.1 Implementation Status of Transportation Control Measures (TCM) 

TCM 1 – Improved Public Transit

The Transit measure commitments included in the 1982 SIP were fully implemented by 1995. 

Transit improvements have continued since that time, as follows. Bus revenue miles5 in San Diego 

County increased 7% from 1995 to 2005, totaling nearly 28 million miles. In the last five years, the 

County’s two largest transit providers have redirected service from low-ridership to high-ridership 

routes. Further, rail transit services, including the San Diego Trolley6 and the Coaster7 commuter 

rail service, have grown by nearly 42% since 1997, reaching over 8.2 million revenue car miles by 

2005. The six-mile extension of the San Diego Trolley, from Qualcomm Stadium in Mission 

Valley to San Diego State University and La Mesa, opened in 2006. Additionally, construction 

began in 2004 on the 22-mile Sprinter Rail Line, connecting Oceanside to Escondido, and it is 

scheduled to begin revenue service in December 2007. 

Notwithstanding these important improvements, it should be understood that the region’s generally 

low-density land use pattern currently does not support extensive deployment of fixed-rail rapid 

transit modes that could provide faster travel times that are more comparable to the personal 

automobile. The San Diego region’s existing transit network, although extensive, is mostly 

composed of lower-speed transit modes (such as conventional transit buses) that are appropriate for 

the lower-density land use levels that exist. The region’s transit strategy, articulated in SANDAG’s 

Regional Comprehensive Plan, is to increase land use densities and transit ridership in town centers 

and particular corridors. In most parts of the region, this system will take several decades to 

mature. 

SANDAG’s Regional Transportation Plan (RTP), MOBILITY 2030, envisions adding a new transit 

mode called Bus Rapid Transit (BRT). BRT would utilize a new class of coaches to provide shorter 

travel times and more convenience than current conventional buses, offering service more similar to 

light rail, but using the streets. Improved travel times will be accomplished by utilizing High 

Occupancy Vehicle lanes and transit prioritizing schemes for traffic signals. 

TCM 2 – High Occupancy Vehicle (HOV) Lanes

Currently, three freeways (I-5, I-15, and SR 54) in the San Diego region have HOV lane segments. 

HOVs are also provided with preferential lanes at 62% of the 276 metered on-ramps, and there is a 

buses-only lane at the SR-163 on-ramp from downtown San Diego. The RTP calls for the 

development of a more robust HOV/Managed Lanes network, as follows: 

● Managed lane facilities on: 

− I-5 from I-805 to Vandegrift Blvd; 

− I-15 from SR 163 to SR 78; 

− I-805 from SR 905 to I-5; 

− SR 52 from I-15 to SR 125. 

 

5 Revenue (car) miles are the total distance that a fleet travels while available for passenger service. 

6 The San Diego Trolley is a 54-mile light rail transit system serving southern San Diego County. 

7 The Coaster is a 42-mile passenger rail line between Oceanside and Downtown San Diego that began service in 1996. 

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● One HOV lane in each direction on: 

− I-5 from SR 905 to I-805; 

− I-8 from SR 125 to 2nd Street; 

− SR 52 from I-805 to I-15; 

− SR 54/SR 125 from I-5 to SR 94; 

− SR 56 from I-5 to I-15; 

− SR 78 from I-5 to I-15; 

− SR 94/125 from I-5 to I-8. 

● Direct HOV to HOV connectors are included at the following freeway interchanges: 

− I-5 to I-805: North to North & South to South; 

− I-15 to SR 78: East to South & North to West; 

− I-15 to SR 94: South to West & East to North; 

− I-805 to SR 52: West to North & South to East. 

Managed lanes will provide priority to HOVs such as carpools and vanpools, regular transit 

services, and a BRT system. Excess capacity in these lanes will be "sold" to solo drivers for a fee, 

similar to the current FasTrak program on I-15. The managed lanes will be separated from the 

general purpose lanes by a barrier with access provided at several locations through openings in the 

barrier. 

TCM 3 – Employer-Based Transportation Management Plans 

In the 1982 SIP, the Employer-Based Transportation Management Plans measure (TCM 3) was 

combined with the Shared-Ride Services measure (TCM 8) to form a more comprehensive measure, 

the “Ridesharing” TCM. The Ridesharing TCM commitments included in the 1982 SIP were fully 

implemented by 1988. 

Traffic Abatement Plan requirements of APCD Rule 132 were included as part of the Ridesharing 

TCM. Pursuant to federal requirements for abating air pollution emergency episodes,8 employerbased Traffic Abatement Plan measures are triggered by ozone levels exceeding 0.35 ppm. No 

ozone concentrations of this level or higher have been recorded in San Diego County since 1979. 

TCM 4 – Trip-Reduction Ordinances 

A regional trip-reduction ordinance was adopted by APCD as part of the 1994 Ozone SIP, but was 

rescinded in 1995 when federal and State laws were amended eliminating the mandate for such 

measures based on public opposition. (It should be noted that this TCM focuses on addressing 

weekday commute trips, whereas San Diego’s exceedances of the eight-hour ozone NAAQS occur 

disproportionately more frequently on weekends (see Section 4.3.1). 

TCM 5 – Traffic Flow Improvements to Reduce Emissions 

Traffic Flow Improvements mostly consist of traffic signal improvements to reduce idling and 

associated emissions. The Traffic Flow Improvements TCM commitments included in the 1982 

SIP were fully implemented by 1990. 

 

8 40 CFR 51.150 et seq. 

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Further implementation of the Traffic Flow Improvements TCM continues. All federally funded 

traffic signal projects selected with the federal transportation funding program (TEA-21) have been 

implemented (117 projects). SANDAG’s 2006 Regional Transportation Improvement Program 

(RTIP) contains $19.7 million in traffic flow improvements, including eight traffic signal projects 

(two highway, six local). 

TCM 6 – Park-and-Ride Facilities

Currently, there are 66 park-and-ride lots in the San Diego region, with 4,049 spaces available. 

More lots are anticipated as funding becomes available. In addition, transit parking at commuter 

rail stations has been developed and is currently available at six stations, with 6,300 spaces 

available. The San Diego Trolley also provides parking at over half (28) of its stations, with 9,700 

confirmed spaces and an undetermined amount of shared-use parking. The future Sprinter rail line 

will offer parking at 13 stations accommodating 1,500 parking spaces. 

TCM 7 – Peak-Period Vehicle Restrictions in Downtown Areas 

This measure is feasible only in high-density portions of compact metropolitan areas with an 

extensive transit system. Given the San Diego region’s historically low-density land use pattern, 

and therefore longer transit travel times, this measure is not yet feasible. However, SANDAG’s 

Smart Growth Incentive Program provides funding to cities for infrastructure projects which 

enhance alternatives to driving in higher density areas. (It should be noted that this TCM focuses 

on addressing peak-period (weekday) trips, whereas San Diego’s exceedances of the eight-hour 

ozone NAAQS occur disproportionately more frequently on weekends (see Section 4.3.1)). 

TCM 8 – Shared-Ride Services 

As mentioned above, in the 1982 SIP, TCM 8 was combined with TCM 3 in a “Ridesharing” TCM. 

The Ridesharing TCM commitments included in the 1982 SIP were fully implemented by 1988. 

Further implementation of Shared-Ride Services TCM continues. SANDAG and APCD are 

partners in the support of RideLink (www.ridelink.org), the regional transportation assistance 

program, charged with providing shared ride services and education to employers and individuals 

on all ridesharing and biking options. Example services include: 

• Carpool Ride Matching Service – computerized ride-matching. 

• Guaranteed Ride Home Service – qualifying ride sharers are provided with three vouchers 

per year for $3 taxi fares or 24-hour rental cars to travel home to address a personal 

unscheduled event. 

• Promotion of Teleworking and Alternative Work Schedules (see TCM 13) – RideLink 

works with employers and employees to create programs for offering alternative work 

arrangements (such as flex time and teleworking) to reduce commute trips and peak hour 

traffic congestion. 

• Park and Ride Programs (see TCM 6) – Caltrans and other agencies provide park and ride 

facilities, which are promoted by RideLink. 

• Vanpool Program – SANDAG operates a Regional Vanpool Program, funded in part by The 

District’s Vehicle Registration Fund. As of November 1, 2006, 537 vanpools were 

operating in the San Diego region carrying more than 4,600 passengers daily, a 19% 

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3.0 Emission Control Strategy

increase over 2005 levels. Vanpools are anticipated to grow at 6 net vanpools per month. 

Additional vanpools are anticipated as additional funding becomes available. 

TCM 9 – Road Surface Restrictions for Motor Vehicles in Metro Areas

Numerous examples of road surface restrictions exist in the San Diego region. In downtown San 

Diego, C Street is limited to the Trolley and pedestrian use, and a block of B Street was closed and 

transformed into the Civic Center Concourse. In Old Town San Diego State Historical Park, 

portions of San Diego Avenue, Calhoun Street, and Mason Street have been restricted to pedestrianonly use. In Balboa Park, the eastern end of El Prado is also restricted to pedestrian-only use. 

North of Sorrento Valley, a segment of Sorrento Valley Road is closed to traffic and reserved for 

bicycle and pedestrian uses. This measure is also implemented on a limited or recurring temporary 

basis for certain recreational areas, weekly farmer’s markets, and yearly festivals/street fairs. 

TCM 10 – Bicycle Facilities 

The Bicycling TCM commitments included in the 1982 SIP were fully implemented by 1995. 

However, further implementation of the Bicycling TCM continues. The bikeway system currently 

includes 1,136 miles of bikeways in the San Diego region, consisting of Class I (exclusive bicycle 

path separated from roadway), Class II (striped on-street bicycle lane), and Class III (shared with 

motor vehicles) facilities. Additionally, front-mounted bike racks are available on nearly all transit 

buses. SANDAG maintains a system of 580 bicycle lockers throughout the region available for 

commuters at transit centers and park-and-ride facilities. 

TCM 11 – Idling Controls 

ARB has adopted diesel-fueled vehicle idling limitation programs focusing on school buses 

(www.arb.ca.gov/toxics/sbidling/sbidling.htm), trucks (www.arb.ca.gov/msprog/truck-idling/truckidling.htm), and locomotives (www.arb.ca.gov/railyard/ryagreement/ryagreement.htm). More 

information is available on ARB’s website at the specified web addresses. 

TCM 12 – Vehicle Cold Start Emissions in Extreme Cold Conditions

This measure is not applicable due to the mild climate in the San Diego region. 

TCM 13 – Flexible Work Schedules 

This measure has been implemented by the RideLink program, as previously identified under TCM 

8. (See www.ridelink.org/Employer_Services/Alternative_Schedules.asp) RideLink staff work 

with employers and employees to create programs for offering alternative work arrangements (such 

as flex time and teleworking) to reduce commute trips and peak hour traffic congestion. 

TCM 14 – Programs and Ordinances Facilitating Non-Automotive Travel 

This measure has been implemented in San Diego via the Regional Comprehensive Plan (RCP), 

adopted by SANDAG, which emphasizes greater reliance on non-automotive travel through 

increased development densities, more mass transit usage, and increased bicycling and walking for 

transportation. Pursuant to the RCP, SANDAG has designated existing and potential Smart Growth 

Areas, and provides funding incentives for local jurisdictions to increase densities and provide for 

mixed uses and additional transit, bicycling and walking facilities in these areas. The largest city in 

the region, the City of San Diego, is in the final stages of adopting a general plan revision consistent 

with this approach. Developers in the region have responded to these policies, and to market forces, 

by initiating a number of large-scale smart growth developments ultimately representing over 

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40,000 new housing units. Additionally, thousands of new units have been added to existing 

communities well-served by transit and amenable to non-motorized travel. 

Additionally, in 2004, voters extended the region’s half-cent sales tax ordinance for transportation 

(“TransNet”), and added additional funding categories, including the Smart Growth Incentive 

Program, and transit, bicycling, and pedestrian improvements. The ordinance requires routine 

accommodation of these modes for all TransNet-funded local roadway projects. 

TCM 15 – Paths or Areas Encouraging Non-Motorized Travel 

The San Diego region has implemented an extensive network of bicycling facilities, many of which 

also serve pedestrians. Additionally, three regional, multi-use trails are still under development—

the Bayshore Bikeway (26 miles around the San Diego Bay), the Inland Rail Trail (22 miles from 

the Escondido Transit Center to the Oceanside Transit Center), and the Coastal Rail Trail (44 miles 

from northern Oceanside to downtown San Diego). These three trails are expected to be used by 

commuters as well as recreational users. Additionally, due to land use plans, regional transportation 

funding formulas, and the nature of the housing market, a number of new smart growth 

developments have been built which include paths and trails that encourage non-motorized travel 

(see TCM 14). 

TCM 16 – Removal of Older, Higher-Polluting Light Duty Vehicles 

Under a program administered by the District using Vehicle Registration Fee funds, a total of 4,277 

older vehicles were permanently retired through 2005, resulting in an estimated reduction of 470 

tons of ozone-precursor emissions. Further, a State-run vehicle retirement program continues, 

administered by the California Department of Consumer Affairs’ Bureau of Automotive Repair 

(www.smogcheck.ca.gov/stdpage.asp?Body=/Consumer/cap_program.htm). 

3.4.3.2 Emission Reduction Potential of Transportation Control Measures

Trip Reduction Ordinances alone (TCM 4) have been estimated to reduce on-road vehicle emissions 

by less than 2%.9 That analysis also estimated that all other TCMs combined would not be more 

effective than Trip Reduction Ordinances (i.e., would not provide combined emission reductions 

exceeding 2%). 

Consequently, it is assumed that the maximum emission reduction potential of implementing all 

unimplemented TCMs (TCMs 4, 7, and 12) would be 2% of on-road vehicle emissions. Projected 

on-road motor vehicle emissions in San Diego County in 2008 are 51 tons per day of VOC and 102 

tons per day of NOx (see Table A-1 in Attachment A). Therefore, the maximum emissions 

reduction potential of implementing all unimplemented TCMs, assuming a 2% reduction in on-road 

emissions, is an estimated 1 ton per day reduction of VOC emissions and 2 tons per day reduction 

of NOx emissions. 

3.4.4 RACM Analysis 

To determine whether additional control measures could advance the attainment year, the additional 

emission reduction increment that would be necessary to advance the attainment year must be 

 

9 “Transportation Control Measures for the Air Quality Plan,” San Diego Association of Governments, 1992. 

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estimated. The potential total emission reductions that could be provided by the additional control 

measures can then be compared to the necessary emission reduction increment to determine 

whether implementing the additional control measures could advance the attainment year. 

Pollutant transport from the South Coast Air Basin contributes significantly to ozone exceedances 

in the San Diego nonattainment area (see Section 1.4.2). Due to the effects of the transport 

contribution, the emission reduction increment that would be necessary from sources within San 

Diego County to advance the attainment year will be greater (to compensate for transport 

emissions) than if ozone exceedances were caused solely by local emissions. Thus, for purposes of 

this RACM analysis, emissions contributing to San Diego’s eight-hour ozone nonattainment are 

assumed to be the total of emissions from San Diego County and South Coast combined. 

The increment of additional emission reductions that would be necessary in 2007 to advance the 

attainment year from 2008 to 2007 is the amount by which total contributing emissions projected 

for 2007 are greater than projected emissions for 2008 (preliminarily considered to be the earliest 

attainment year). For San Diego and South Coast combined, projected 2007 emissions are greater 

than 2008 emissions by 44 tons per day of VOC and 58 tons per day of NOx (see Table 3-8). Thus, 

44 tons per day of additional VOC reductions and 58 tons per day of additional NOx reductions 

would be necessary in 2007 to advance the attainment year from 2008 to 2007. 

As shown in Table 3-8, San Diego County-only emissions in 2007 are projected to be higher than 

2008 by about 5 tons per day of VOC and 6 tons per day of NOx. Consequently, in the rarer 

circumstances where exceedances of the eight-hour ozone NAAQS are caused solely by local San 

Diego County emissions, 5 tons per day of additional VOC reductions and 6 tons per day of 

additional NOx reductions would be necessary in 2007 to advance the attainment year from 2008 to 

2007. 

TABLE 3-8 

Projected Total Daily Emissions in 2007 versus 2008 

VOC Emissions (tons per day) NOx Emissions (tons per day) 

Region* 2007 2008 Difference 2007 2008 Difference 

SD plus SC 862 818 44 1090 1032 58 

SD Only 173 168 5 201 195 6 

*SD = San Diego Air Basin; SC = South Coast Air Basin 

Source: ARB SIP emissions inventory. 

Due to the long lead time required for rule or program development, adoption, and implementation, 

none of the control measures listed in Tables 3-6 (stationary source measures) and 3-7 

(transportation source measures) could be implemented by the beginning of 2007. Consequently, 

none of those measures are considered “reasonably available” to advance the attainment year from 

2008 to 2007. Furthermore, even if the measures in Tables 3-6 and 3-7 could be implemented in 

time, these measures would cumulatively provide less than 11 tons per day of VOC reductions and 

less than 4 tons per day of NOx reductions.10 This is less than the additional emission reduction 

 

10 The indicated maximum emission reduction potential is derived by summing the reductions listed in Table 3-6 and 

the values presented in Section 3.4.3.2. The calculations are presented in Attachment E. 

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3.0 Emission Control Strategy

increments that would be necessary to advance the attainment year for both the San Diego-only and 

South Coast plus San Diego scenarios. Consequently, those measures would not be considered 

reasonably available and are not required to be included in the SIP. 

Nevertheless, as discussed in Section 3.3, the District is currently planning to adopt the Low VOC 

Solvent Cleaning control measure, to be implemented in 2008, to satisfy State requirements for 

every feasible control measure and to assist in reducing ozone concentrations in 2008 to below the 

level of the eight-hour ozone NAAQS. 

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4.0 Attainment Demonstration

4.0 ATTAINMENT DEMONSTRATION 

4.1 BACKGROUND 

The Attainment Demonstration summarizes the results of photochemical air quality simulation 

modeling and supplemental Weight of Evidence analyses to demonstrate that the Emission Control 

Strategy (Section 3.0) to reduce ozone-precursor emissions is sufficient to provide for attainment of 

the eight-hour ozone NAAQS in San Diego County as expeditiously as practicable, pursuant to 

CAA requirements. The Attainment Demonstration was developed pursuant to EPA’s Guidance on 

the Use of Models and Other Analyses in Attainment Demonstrations for the eight-hour Ozone 

NAAQS (October 2005). 

Ozone formation in the atmosphere is a complex photochemical process, and sophisticated 

photochemical air quality simulation modeling is a valuable tool to help predict the amount of 

precursor emission reductions needed to provide for attainment of the eight-hour ozone NAAQS. 

The air quality model is computer-driven and simulates weather patterns, emissions, and 

photochemical processes in the atmosphere to predict future ozone levels in the region. 

As with other predictive tools, photochemical air quality simulation modeling has inherent 

uncertainties and can not be expected to produce absolutely accurate results. Such models require 

detailed three-dimensional and time-varying inputs of emissions and meteorological data for the 

days being considered. Limitations in these inputs, as well as limitations in the model’s 

formulations for simulating photochemical reactions, pollutant dispersion, and deposition lead to 

uncertainties in model predictions.1

To address the inherent modeling uncertainties, EPA Guidance established comprehensive 

procedures for demonstrating attainment of the eight-hour ozone NAAQS. These procedures differ 

in two major ways from past attainment demonstrations for the former one-hour ozone NAAQS. 

1. The new Modeled Attainment Test is based on relative, rather than absolute, use of the 

modeling results. That is, the test relies on the ability of the photochemical modeling system to 

simulate the change in ozone due to emission reductions, rather than considering the modeling 

results to represent exact values for future-year ozone concentrations. Specifically, the model is 

run for both the 2002 baseline conditions and future 2008 scenario. The results of the baseline 

and future scenario model runs are compared to derive “Relative Response Factors,” which 

predict the relative reduction in ozone concentrations between 2002 and 2008 resulting from 

control strategy implementation in the future year. The Relative Response Factors are then 

applied to monitored base-year (2002) design values to produce predicted future-year (2008) 

design values. The Modeled Attainment Test is “passed” if the predicted future-year design 

values at each site are below 85 parts per billion (ppb).2 The future-year design value 

represents the fourth highest eight-hour average ozone concentration in the forecast attainment 

year. 

 

1 According to EPA’s Guidance document, past modeling analyses have shown that future ozone design value uncertainties of 2 to 4

parts per billion can result from use of alternate, yet equally appropriate, emissions inputs, chemical mechanisms, and meteorological 

inputs. 

2 Equivalent to 0.085 parts per million. Eight-hour ozone levels are usually identified in terms of parts per million (ppm), as

reflected in Sections 1 through 3. However, EPA guidance uses parts per billion (ppb) for purposes of discussing photochemical air 

quality simulation modeling. Accordingly, ozone concentrations are identified in ppb for purposes of this Section 4.0. 

Eight-Hour Ozone Attainment Plan Page 4-1 
4.0 Attainment Demonstration

2. In recognition of the inherent uncertainties (described above) in the Modeled Attainment 

Test, the Attainment Demonstration must also include a Weight of Evidence Demonstration 

incorporating a variety of statistical and other analyses—such as monitored air quality and 

emissions trends and meteorological analyses—that provide additional persuasive support to a 

conclusion that the Control Strategy is sufficient to provide for timely attainment. Further, as 

specified in EPA Guidance, in areas where the Modeled Attainment Test is narrowly failed—

that is, showing future-year design values above 85 but below 88 ppb—the Weight of Evidence 

Demonstration can be used to demonstrate timely attainment. 

4.2 RESULTS 

As discussed in detail below, the Modeled Attainment Test predicts a 2008 Design Value in San 

Diego County of 86 ppb, which narrowly exceeds the attainment threshold of less than 85 ppb, but 

is well within the allowable range (less than 88 ppb) for demonstrating expeditious attainment with 

supplemental Weight of Evidence analyses. Pursuant to EPA Guidance, this Attainment 

Demonstration incorporates a supplementary Weight of Evidence Demonstration. The resulting 

evidence indicates that the Emission Control Strategy is adequate to reduce ozone concentrations to 

below the level of the eight-hour ozone NAAQS by the statutory attainment deadline of June 15, 

2009. 

4.3 MODELED ATTAINMENT TEST 

The Modeled Attainment Test predicts whether or not estimated ozone design values in the air basin 

in 2008 (the first full ozone season prior to the June 15, 2009, attainment deadline), under 

meteorological conditions similar to those simulated in the model, will be less than or equal to the 

concentration level specified in the ozone NAAQS. Specifically, if estimates of 2008 future-year 

ozone concentrations are predicted to be below 85 ppb, then the Modeled Attainment Test is 

satisfied. 

The Modeled Attainment Test is site-specific and, therefore, must be performed for each monitoring 

site in the nonattainment area. In San Diego County, only the Alpine monitoring site violates the 

eight-hour ozone NAAQS. The Alpine monitoring site is located in the inland foothills at an 

elevation of approximately 2,000 feet. Other monitoring sites in the county have occasionally 

recorded exceedances of the eight-hour ozone NAAQS, but not frequently enough to violate the 

standard. 

The 2002 baseline ozone design value used in the Modeled Attainment Test is the average of the 

design values for 2002 (based on 2000-2002 data), 2003 (2001-2003 data), and 2004 (2002-2004). 

EPA recommends averaging the three design values to smooth the impact of weather-related 

variability and provide a more representative air quality baseline. For the Alpine monitoring site, 

the 2002 baseline ozone design value equates to 92.3 ppb. 

4.3.1 Episodes

The Modeled Attainment Test itself must also account for day-to-day variability of meteorology. 

Several different “episode” days, with representative high eight-hour ozone concentrations, must be 

Eight-Hour Ozone Attainment Plan Page 4-2 
4.0 Attainment Demonstration

modeled to incorporate a variety of meteorological conditions that are conducive to producing high 

ozone concentrations in the area. EPA Guidance recommends modeling ten or more episode days if 

possible, but at least five episode days must be modeled. 

As discussed below, six days from two different episodes are reflected in the Modeled Attainment 

Test for this Attainment Demonstration. The selected episodes were drawn from the 1997 Southern 

California Ozone Study (SCOS97). SCOS97 was an intensive comprehensive air quality and 

meteorological data gathering effort, which involved supplemental monitoring sites for ozone and 

its precursors and meteorological parameters, as well as aircraft-based monitoring. The episodes 

were selected from the SCOS97 period because the richer database from SCOS97 provides the 

more detailed three-dimensional time-varying data needed for developing and evaluating adequate 

air quality simulation modeling applications. 

San Diego County experienced a substantial drop in ozone exceedances in the year of the field 

study, 1997. Nevertheless, the District was able to derive two relatively high-ozone episodes from 

the SCOS97 database, as described below. These two episodes provide a sufficient number of 

episode days (six) for modeling purposes. 

August 4-7, 1997 (Local Plus Transport), is an ozone episode where both local contributions and 

transport from the South Coast Air Basin (to the north) contributed to ozone exceedances in San 

Diego County. The highest eight-hour averaged ozone concentration measured at an EPA-approved 

official monitor was 87 ppb at Alpine on August 5. 

September 27-28, 1997 (Weekend), is a weekend episode. Exceedances of the ozone standard on 

weekends are important in San Diego County. In 2006, 57% of the days with exceedances of the 

eight-hour ozone NAAQS were on Saturday or Sunday. Both local sources and transport 

contributed to the exceedances during this episode. Eight-hour average ozone levels did not reach 

85 ppb at EPA-approved monitors during this episode. The highest eight-hour average ozone 

concentration at Alpine during this episode was 83 ppb on September 28. 

Ramp-Up Days. Pursuant to EPA Guidance, additional “ramp-up” days (August 3, September 25-

26) just prior to the selected episodes were included in the modeling to allow the modeling system 

to fully initialize and stabilize before simulating the episode days of concern. As specified by EPA, 

the modeled results for ramp-up days were excluded from the calculation of relative response 

factors. 

EPA further recommends that the episode days have 2002 model-predicted concentrations of 

85 ppb or more, although including episode days with lower concentrations of at least 70 ppb is 

acceptable. Due to 1997 being such a clean year, only three of the episode days have 2002 modelpredicted concentrations greater than 85 ppb. However, all six episode days have 2002 modelpredicted concentrations of at least 70 ppb. 

Detailed documentation of the photochemical modeling performance evaluation and the 2002 baseyear and 2008 attainment-year simulation modeling are presented in Attachment H. The modeling 

protocols are in Attachment I. 

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4.0 Attainment Demonstration

4.3.2 Model-Predicted 2008 Design Value

EPA Guidance specifies the following steps for calculating the Relative Response Factor. 

1. Identify the model-predicted daily maximum eight-hour ozone concentration representing 

the monitoring site for each episode day for 2002 and 2008. 

2. Calculate the average of the model-predicted eight-hour ozone concentrations over all the 

episode days for 2002 and 2008. 

3. Calculate the 2002-to-2008 Relative Response Factor by dividing the 2008 averaged modelpredicted eight-hour ozone concentration by the 2002 averaged model-predicted eight-hour 

ozone concentration. 

The Model-Predicted 2008 Design Value is then calculated by multiplying the 2002-to-2008 

Relative Response Factor by the actual monitored 2002 baseline design value, which is 92.3 ppb at 

the Alpine site. EPA Guidance specifies that the Model-Predicted 2008 Design Value is truncated 

to the whole ppb value prior to being compared to the eight-hour ozone NAAQS. Calculations of 

the Model-Predicted 2008 Design Value at the Alpine Monitoring Site are presented in Table 4-1. 

TABLE 4-1 

Calculation of Model-Predicted 2008 Design Value at Alpine Monitoring Site 

(parts per billion) 

Date 2002 2008 RRF* Baseline 2008 

Predicted 

August 4 75.1 71.4 0.951 92.3 87 

August 5 92.5 87.1 0.942 92.3 86 

August 6 106.7 100.4 0.941 92.3 86 

August 7 91.8 86.2 0.939 92.3 86 

September 27 72.8 68.1 0.935 92.3 86 

September 28 73.7 68.3 0.927 92.3 85 

6-Day Average of Aug 4,5,6,7,Sep 27,28 85.4 80.3 0.940 92.3 86 

*RRF = Relative Response Factor 

The Modeled Attainment Test predicts a 2008 Design Value of 86 ppb, which is narrowly higher 

than the attainment threshold of below 85 ppb. However, due to inherent modeling uncertainties as 

described above, this Attainment Demonstration incorporates a supplementary Weight of Evidence 

Demonstration that persuasively demonstrates, based on a preponderance of all available evidence, 

that the Existing Control Strategy is sufficient to reduce ozone concentrations in the area to below 

the level of the eight-hour ozone NAAQS by the 2008 attainment year. 

4.4 WEIGHT OF EVIDENCE DEMONSTRATION 

Pursuant to EPA Guidance, a Weight of Evidence Demonstration includes a variety of statistical 

and other analyses that provide additional persuasive support to a conclusion that the Control 

Strategy is sufficient to provide for timely attainment. This Weight of Evidence Demonstration 

Eight-Hour Ozone Attainment Plan Page 4-4 
4.0 Attainment Demonstration

includes additional modeling results, statistical air quality trends analyses, graphical air quality 

trends analyses, and meteorological analyses of both a recent “clean year” (2004, with eight-hour 

ozone levels below the level of the NAAQS) and the unusually hot and high ozone season in 2006. 

Results of each analysis have been considered in concert, along with results of the Modeled 

Attainment Test, to determine that the Existing Control Strategy is sufficient to reduce ozone 

concentrations throughout the county to below the level of the eight-hour ozone NAAQS by 2008, 

thus providing a demonstration of attainment by the June 15, 2009, statutory deadline. 

4.4.1 Weight-of-Evidence Analyses Involving Modeling Results

Pursuant to EPA Guidance, this Weight of Evidence Demonstration incorporates several analyses 

involving modeling results beyond those considered in the Modeled Attainment Test. The 

supplemental modeling analyses include: 

1. Consideration of model-predicted future ozone concentrations in areas not near a monitor. 

2. Modeled Ozone Exposure Reduction Metric. 

4.4.1.1 Unmonitored Area Analysis 

The Modeled Attainment Test is designed to focus on monitoring sites and thus does not consider 

future ozone concentrations in areas that are not near a monitor. To address this possible 

discrepancy, EPA Guidance recommends a procedure for predicting future ozone concentrations in 

areas that are not near a monitor. The focus of the recommended procedure is to identify areas 

where the model predicts ozone concentrations significantly higher than those predicted near a 

monitor. 

As can be seen in Table 4-2, the maximum 2008 eight-hour ozone concentration predicted within 

San Diego County was near the Alpine monitoring site on four of the six episode days. On the 

other two episode days, the maximum 2008 eight-hour concentration in the county is only about 2 

ppb greater than the concentration predicted for the Alpine monitoring site. Consequently, the 

modeling indicates that Alpine adequately represents the maximum eight-hour ozone concentrations 

predicted within San Diego County. Therefore, no additional analyses are needed to address areas 

away from a monitor. 

Eight-Hour Ozone Attainment Plan Page 4-5 
4.0 Attainment Demonstration

TABLE 4-2 

Comparison of Maximum Predicted 2008 Ozone Concentration in San Diego County to 

Concentration Predicted Near Alpine Monitoring Site 

(parts per billion) 

Episode Day Countywide Maximum Near Alpine Monitoring Site 

August 4 73.7 71.4 

August 5 88.6 87.1 

August 6 100.4 100.4 

August 7 86.2 86.2 

September 27 68.1 68.1 

September 28 68.3 68.3 

4.4.1.2 Modeled Ozone Exposure Reduction Metric 

EPA Guidance identifies various optional metrics that can be considered as part of a Weight of 

Evidence Demonstration. One such metric—percent change in total amount of ozone ≥ 85 ppb 

within the nonattainment area—addresses both the frequency and magnitude of eight-hour ozone 

nonattainment and was evaluated. This metric is defined as the change between 2002 and 2008 in 

the sum total (in ppb), over all grid cells3 within the nonattainment area and for all hours of the 

episode days, of the amount by which the modeled ozone concentration in each grid cell exceeds 

85 ppb. Three of the six episode days (August 4, September 27-28) modeled for San Diego County 

do not have 2002 base-year modeled ozone levels exceeding 85 ppb, and therefore a modified 

metric using a 70 ppb minimum threshold (in lieu of 85 ppb) was applied to assess the modeled 

reductions in unhealthful ozone exposure on those three episode days.4 

The final EPA Guidance does not specify a minimum percent reduction in the metric to support a 

Weight of Evidence Demonstration of attainment. An early draft version of the Guidance (1999) 

indicates “[a]n 80% reduction in this measure may be regarded as an example of a ‘large’ 

reduction.” Since the final EPA Guidance does not specify a suggested benchmark level, this 

Weight of Evidence Demonstration does not strictly rely on an 80% reduction level as a threshold 

for evaluating the modeling, but does indicate how many of the modeling days exceed an 80% 

reduction level. 

As shown in Tables 4-3 and 4-4, more than 80% reduction in the ozone exposure metric was 

predicted on five of the six modeled episode days, with a greater than 50% reduction on the 

remaining day, reflecting substantial reductions in ozone exposure and supporting this Weight of 

Evidence demonstration. 

 

3 For modeling purposes, San Diego County was divided into 5-kilometer squares, called grid cells. 

4 70 ppb is consistent with the minimum level for selecting episode days (see Section 4.3.1), and is also the level of the 

California State eight-hour ozone standard. 

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4.0 Attainment Demonstration

TABLE 4-3 

Total Eight-Hour Averaged Ozone Above 85 ppb 

Aggregated Over All Grid Cells in San Diego County 

For the August 5-7 Ozone Episode Days 

Date 2002 Simulation 

(ppb) 

2008 Simulation 

(ppb) 

Change in Metric 

(ppb) 

Percent 

Change 

August 5 2383 104 -2279 -96% 

August 6 3698 1764 -1934 -52% 

August 7 328 5 -323 -98% 

TABLE 4-4 

Total Eight-Hour Averaged Ozone Above 70 ppb 

Aggregated Over All Grid Cells in San Diego County 

For the August 4 and September 27-28 Ozone Episode Days 

Date 2002 Simulation 

(ppb) 

2008 Simulation 

(ppb) 

Change in Metric 

(ppb) 

Percent 

Change 

August 4 1068 75 -993 -93% 

Sept 27 65 0 -65 -100% 

Sept 28 468 60 -408 -87% 

4.4.2 Air Quality Trends Data 

This element of the Weight of Evidence Demonstration includes five statistical analyses of EightHour Ozone Design Values, which indicate ozone levels can be expected to be reduced to below 85 

ppb by 2008. Numerous graphical analyses illustrating the continuing downward trends in ozone 

and precursor concentrations are also presented. 

4.4.2.1 Eight-Hour Ozone Design Values Trends Statistical Analyses 

The District performed several air quality trends statistical analyses of the monitored eight-hour 

ozone design values at the Alpine monitoring site (the only site at which violations of the eight-hour 

ozone NAAQS have been observed), using a variety of ozone data samples reflecting different 

groups of years. The best-fit trend line through each data sample was calculated, and the formula 

for that trend line was used to extrapolate the trend line to determine a projected attainment year 

based on that sample. 

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4.0 Attainment Demonstration

The first sample reflects all years in ARB’s monitored air quality database, 1977-2006. (See Figure 

4-1 below.) Based on this sample, attainment would be projected to occur in 2007 with an 

extrapolated ozone design value of 84.8 ppb. 

FIGURE 4-1 

 

A more optimistic sample providing a slightly steeper trend line, starting with the 1980 peak and 

ending with the 2005 low value (Figure 4-2), projects attainment in 2006 with an extrapolated 

ozone design value of 84.7 ppb. 

FIGURE 4-2 

 

Eight-Hour Ozone Attainment Plan Page 4-8 
4.0 Attainment Demonstration

A more conservative sample providing a flatter trend line (Figure 4-3), starting in 1997 and 

ending in 2006, projects attainment in 2008 with an extrapolated ozone design value of 83.4 ppb. 

FIGURE 4-3 

Eight-Hour Ozone Attainment Plan Page 4-9 
4.0 Attainment Demonstration

To obtain another perspective on ozone air quality trends, regression analyses were performed 

relating the eight-hour ozone design values to their associated ozone precursor emissions (VOC 

+ NOx) for 1990 through 2006. Figures 4-4 and 4-5 illustrate that precursor emissions correlate 

highly with measured ozone design values. In Figure 4-4, considering precursor emissions from 

within San Diego County only, the best-fit regression line projects attainment in 2006 with a 

regression-projected ozone design value of 84.7 ppb. 

Eight-Hour Ozone Attainment Plan Page 4-10 
4.0 Attainment Demonstration

Lastly, using the combined emissions from both the San Diego and upwind South Coast air districts 

(Figure 4-5) yields a similar but more optimistic result, with a regression-projected 2006 ozone 

design value of 83.7 ppb. 

The high R2

 values (0.87 to 0.96) identified in Figures 4-1 through 4-5 indicate the data within each 

graph are well correlated and each air quality trend line has excellent predictive value. These 

statistical analyses provide strong evidence that the Existing Control Strategy will reduce ozone 

levels to below the level of the eight-hour ozone NAAQS by the 2008 attainment year. 

4.4.2.2 Graphical Air Quality Trends Analyses 

A discussion of 20 additional figures, providing a more in-depth review of long-term trends of 

monitoring data for ozone and ambient concentrations of ozone precursors, is presented in 

Attachment F. 

4.4.3. Meteorological Representativeness of Recent Years

In 2004, the Alpine monitor recorded only two exceedances of the eight-hour ozone NAAQS, and 

the fourth highest eight-hour concentration was 0.083 ppm, below the level of the standard. In 

2005, the standard was exceeded five times and the fourth highest eight-hour concentration was 

0.087 ppm, just slightly exceeding the level of the standard. However, due to a record-breaking 

Eight-Hour Ozone Attainment Plan Page 4-11 
4.0 Attainment Demonstration

heat wave, in 2006 the standard was exceeded 14 times and the fourth highest eight-hour 

concentration was 0.094 ppm. Attachment G presents a detailed meteorological analysis of those 

three years (2004, 2005, and 2006), and concludes that the “clean” year 2004 had typical 

meteorology similar to 2005, and thus could be expected to recur during the attainment period. 

Conversely, 2006 was quite anomalous and similar conditions are unlikely to recur in the near 

future. 

4.4.4 Emission Trends

Ozone precursor emissions are projected to continuously reduce through 2020 due to existing, 

ongoing emission control regulations. Figure 4-6 presents San Diego County emission trends for 

the ozone precursors VOC plus NOx, based on currently adopted emission control regulations. 

Figure 4-7 presents combined emission trends for both San Diego County and the South Coast air 

districts to reflect all emissions contributing to San Diego County’s ozone concentrations. These 

continuous improvement trends provide corroborative evidence of the adequacy of the Emission 

Control Strategy to provide for timely attainment (and maintenance) of the eight-hour ozone 

NAAQS in San Diego County. 

Figure 4-6 

San Diego County Emissions Trends

0

100

200

300

400

500

600

700

1990

1992

1994

1996

1998

2000

2002

2004

2006

2008

2010

2012

2014

2016

2018

2020

tons per day

VOC NOx VOC+NOx

Source: ARB SIP emissions inventory, Version 1.06. 

Eight-Hour Ozone Attainment Plan Page 4-12 
4.0 Attainment Demonstration

Figure 4-7 

San Diego + South Coast Emissions Trends

0

500

1000

1500

2000

2500

3000

3500

4000

4500

1990

1992

1994

1996

1998

2000

2002

2004

2006

2008

2010

2012

2014

2016

2018

2020

tons per day

VOC NOx VOC+NOx

Source: ARB SIP emissions inventory, Version 1.06. 

4.4.5 Shortened Ozone Season 

EPA has identified San Diego County (and all of California) as having a 12-month ozone season, 

meaning that ozone levels at any time of year have been capable of exceeding the eight-hour ozone 

NAAQS. However, as presented in Figure 4-8, over the years the length of the ozone season 

(number of days) has been shortening, beginning later and ending earlier. Since 2001, there have 

been no exceedances of the eight-hour ozone NAAQS at the Alpine monitoring site before May or 

after October. The shortening of the ozone season provides additional positive evidence of the 

adequacy of the Emission Control Strategy to provide for timely attainment. 

Eight-Hour Ozone Attainment Plan Page 4-13 
4.0 Attainment Demonstration

Figure 4-8 

ALP 8-Hr Ozone Season: 1980 - 2006

0

30

60

90

120

150

180

210

240

270

300

330

360

19801982198419861988199019921994199619982000200220042006

Year

Julian Dates

First Exceedance Date Last Exceedance Date

4.5 CONCLUSION 

Pursuant to Clean Air Act requirements and EPA Guidance, the District has conducted numerous 

and diverse analyses—including the Modeled Attainment Test, the Unmonitored Area Analysis, 

and several analyses of air quality, emissions, and meteorological data—to judge whether timely 

attainment of the eight-hour ozone NAAQS in San Diego County is likely. The results of the 

Weight-of-Evidence analyses, on balance, provide persuasive support to a conclusion that the 

Existing Control Strategy is sufficient to reduce ozone concentrations throughout San Diego County 

to below the level of the eight-hour ozone NAAQS by the 2008 ozone season. Accordingly, 

attainment by the statutory deadline of June 15, 2009, has been demonstrated. 

Eight-Hour Ozone Attainment Plan Page 4-14 
5.0 Contingency Measures

5.0 CONTINGENCY MEASURES

Contingency Measure requirements are not included by EPA in the Code of Federal Regulations, 

but are discussed in section IV.F. of the preamble of the Final Rule to Implement the 8-Hour Ozone 

National Ambient Air Quality Standard. Areas are required to adopt contingency measures to be 

implemented in the event of failure to meet a RFP milestone or to attain the eight-hour ozone 

NAAQS. It should be noted that the CAA requires States to identify contingency measures that will 

go into effect without further action on the part of the State or EPA. 

Since existing mobile source control measures are projected to continue providing additional 

significant emission reductions for many years beyond the 2008 attainment date as newer vehicles 

enter the fleet, this Eight-Hour Ozone Attainment Plan relies on the continuing emission reductions 

from those existing mobile source control measures to fulfill the Contingency Measures 

requirement. These measures will continue to be implemented regardless of the air basin’s 

attainment status in 2009. 

As indicated in Table 5-1, existing mobile source control regulations will continue reducing San 

Diego County total VOC emissions between 2008 and 2012 by about 2% per year and NOx 

emissions by about 3% per year. Such continuing emission reductions are ample to ensure 

reasonable further progress will continue to be achieved in the event that the area would fail to 

attain the eight-hour ozone NAAQS by the attainment deadline. 

TABLE 5-1 

Projected VOC and NOx Emissions 2008-2012 

(tons per day) 

VOC NOx 

2008 2009 2010 2011 2012 2008 2009 2010 2011 2012

Stationary Sources 31.7 32.2 32.8 33.3 33.9 10.4 10.5 11.0 11.0 11.0 

Areawide Sources 36.3 36.6 36.9 37.2 37.6 1.8 1.8 1.8 1.8 1.8 

Onroad Mobile Sources 51.1 47.9 44.9 42.5 40.2 96.8 92.0 87.0 81.5 75.6 

Offroad Mobile Sources 48.5 46.9 45.6 44.3 43.2 85.8 84.3 82.7 82.1 81.4 

Total 167.6 163.7 160.2 157.4 154.8 194.8 188.6 182.4 176.4 169.9 

Reduction 4.0 3.4 2.8 2.6 6.1 6.2 6.0 6.6 

Percent Reduction 2.4% 2.1% 1.8% 1.6% 3.1% 3.3% 3.3% 3.7% 

Columns may not sum exactly to totals due to rounding. 

Source: ARB SIP emissions inventory. 

Eight-Hour Ozone Attainment Plan Page 5-1 
Attachment A Emission Inventories for 2002 and 2008 

A-1 

ATTACHMENT A 

EMISSION INVENTORIES FOR 2002 AND 2008 

Table A-1 

Emission Inventory of Ozone Precursors in San Diego County 

(tons per day) 

 VOC VOC NOx NOx 

SOURCE CATEGORY 2002 2008 2002 2008

Electric Utilities 0.43 0.70 2.42 3.58 

Cogeneration 1.75 1.84 2.70 2.83 

Manufacturing And Industrial 0.07 0.07 1.05 1.11 

Food And Agricultural Processing 0.02 0.01 0.12 0.10 

Service And Commercial 0.16 0.17 0.99 1.01 

Other (Fuel Combustion) 0.18 0.14 1.44 1.25 

Sewage Treatment 0.04 0.05 0.06 0.07 

Landfills 1.66 1.83 0.17 0.19 

Incinerators 0.00 0.00 0.00 0.00 

Soil Remediation 0.00 0.00 0.00 0.00 

Other (Waste Disposal) 0.23 0.25 0.00 0.00 

Laundering 0.07 0.09 0.00 0.00 

Degreasing 1.64 1.72 0.00 0.00 

Coatings And Related Process Solvents 6.20 6.97 0.00 0.00 

Printing 3.76 4.08 0.00 0.00 

Adhesives And Sealants 3.06 2.64 0.00 0.00 

Other (Cleaning And Surface Coatings) 0.10 0.11 0.00 0.00 

Petroleum Marketing 8.07 8.50 0.01 0.01 

Other (Petroleum Production And Marketing) 0.00 0.00 0.00 0.00 

Chemical 1.32 1.61 0.00 0.00 

Food And Agriculture 0.09 0.09 0.00 0.00 

Mineral Processes 0.14 0.17 0.13 0.15 

Metal Processes 0.00 0.00 0.00 0.00 

Electronics 0.00 0.00 0.00 0.00 

Other (Industrial Processes) 0.56 0.66 0.08 0.08 

Stationary Subtotal 29.56 31.70 9.19 10.38 

Consumer Products 21.94 19.12 0.00 0.00 

Architectural Coatings And Related Process Solvents 11.98 10.54 0.00 0.00 

Pesticides/Fertilizers 1.17 0.85 0.00 0.00 

Asphalt Paving / Roofing 1.78 1.81 0.00 0.00 

Residential Fuel Combustion 0.32 0.33 1.64 1.70 

Farming Operations 1.37 1.37 0.00 0.00 

Fires 0.05 0.05 0.02 0.02 

Managed Burning And Disposal 0.28 0.26 0.09 0.08 

Cooking 1.82 2.00 0.00 0.00 

Areawide Subtotal 40.71 36.34 1.75 1.80 

Eight-Hour Ozone Attainment Plan
Attachment A Emission Inventories for 2002 and 2008 

A-2 

Table A-1 (continued) 

Emission Inventory of Ozone Precursors in San Diego County 

(tons per day)

 VOC VOC NOx NOx 

SOURCE CATEGORY 2002 2008 2002 2008

Light Duty Passenger 37.93 21.43 33.41 18.17 

Light Duty Trucks - 1 6.70 4.18 7.15 4.14 

Light Duty Trucks - 2 13.81 9.54 24.44 14.45 

Medium Duty Trucks 5.86 4.19 10.91 7.35 

Light Heavy Duty Gas Trucks - 1 4.03 2.50 4.14 3.20 

Light Heavy Duty Gas Trucks - 2 0.60 0.45 0.56 0.54 

Medium Heavy Duty Gas Trucks 1.38 0.85 1.37 1.12 

Heavy Heavy Duty Gas Trucks 0.66 0.46 1.62 1.19 

Light Heavy Duty Diesel Trucks - 1 0.01 0.10 0.11 2.54 

Light Heavy Duty Diesel Trucks - 2 0.06 0.08 1.27 1.62 

Medium Heavy Duty Diesel Trucks 0.22 0.27 11.58 10.92 

Heavy Heavy Duty Diesel Trucks 2.15 1.96 27.45 25.01 

Motorcycles 2.97 4.41 0.61 1.16 

Heavy Duty Diesel Urban Buses 0.09 0.09 2.31 2.09 

Heavy Duty Gas Urban Buses 0.04 0.04 0.06 0.07 

School Buses 0.11 0.10 1.16 1.23 

Other Buses 0.18 0.14 0.95 0.85 

Motor Homes 0.56 0.31 1.49 1.10 

Onroad Subtotal 77.35 51.10 130.60 96.77 

Aircraft 3.19 3.24 5.01 5.54 

Trains 0.07 0.08 1.38 1.26 

Ships And Commercial Boats 1.94 1.82 29.34 31.52 

Recreational Boats 19.16 17.89 4.80 6.79 

Off-Road Recreational Vehicles 2.45 3.02 0.08 0.07 

Off-Road Equipment 21.09 18.65 44.51 36.64 

Farm Equipment 1.09 0.83 5.32 3.98 

Fuel Storage And Handling 4.52 2.96 0.00 0.00 

Offroad Subtotal 53.51 48.49 90.44 85.81 

Pre-Baseline Emission Reduction Credits Subtotal 0.63 0.22 

Military Growth Increment 2.33 

TOTAL 201.13 168.25 231.96 197.30 

Source: ARB SIP emissions inventory. 

Eight-Hour Ozone Attainment Plan
Attachment A Emission Inventories for 2002 and 2008 

A-3 

Table A-2 

Emission Inventory of Ozone Precursors in San Diego County 

and South Coast Air Basin Combined 

(tons per day)

 VOC VOC NOx NOx 

SOURCE CATEGORY 2002 2008 2002 2008 

Electric Utilities 2.18 2.41 7.54 11.41 

Cogeneration 1.88 1.96 3.28 3.31 

Oil And Gas Production (Combustion) 0.24 0.24 1.23 0.79 

Petroleum Refining (Combustion) 1.31 1.31 7.07 6.11 

Manufacturing And Industrial 1.76 1.96 18.44 17.18 

Food And Agricultural Processing 0.18 0.11 2.03 1.08 

Service And Commercial 1.47 1.57 18.31 16.35 

Other (Fuel Combustion) 1.06 0.82 9.46 7.61 

Sewage Treatment 0.34 0.38 0.06 0.07 

Landfills 1.75 1.93 0.80 0.86 

Incinerators 0.09 0.10 1.53 1.63 

Soil Remediation 0.00 0.00 0.00 0.00 

Other (Waste Disposal) 7.38 7.35 0.00 0.00 

Laundering 0.25 0.28 0.00 0.00 

Degreasing 21.18 10.72 0.00 0.00 

Coatings And Related Process Solvents 35.02 30.16 0.06 0.07 

Printing 10.05 8.64 0.00 0.00 

Adhesives And Sealants 6.51 6.25 0.00 0.00 

Other (Cleaning And Surface Coatings) 1.49 0.79 0.14 0.17 

Oil And Gas Production 2.50 0.85 0.05 0.33 

Petroleum Refining 4.69 3.75 4.86 4.52 

Petroleum Marketing 35.88 35.55 0.06 0.03 

Other (Petroleum Production And Marketing) 0.01 0.01 0.00 0.00 

Chemical 13.74 12.44 0.09 0.09 

Food And Agriculture 2.86 2.93 0.00 0.01 

Mineral Processes 0.52 0.55 1.34 0.93 

Metal Processes 0.06 0.06 0.36 0.18 

Wood And Paper 0.10 0.10 0.00 0.00 

Glass And Related Products 0.01 0.01 0.03 0.01 

Electronics 0.06 0.09 0.00 0.00 

Other (Industrial Processes) 8.38 8.69 0.79 0.92 

Stationary Subtotal 162.96 142.04 77.57 73.68 

Consumer Products 132.34 116.67 0.00 0.00 

Architectural Coatings And Related Process Solvents 69.28 37.25 0.00 0.00 

Pesticides/Fertilizers 4.05 3.05 0.00 0.00 

Asphalt Paving / Roofing 2.67 2.90 0.00 0.00 

Residential Fuel Combustion 1.79 1.84 22.11 19.72 

Farming Operations 11.24 7.01 0.00 0.00 

Fires 0.28 0.29 0.09 0.09 

Managed Burning And Disposal 0.53 0.51 0.20 0.19 

Cooking 3.61 3.94 0.00 0.00 

Areawide Subtotal 225.80 173.46 22.40 20.00 

Eight-Hour Ozone Attainment Plan
Attachment A Emission Inventories for 2002 and 2008 

A-4 

Table A-2 (continued) 

Emission Inventory of Ozone Precursors in San Diego County and 

South Coast Air Basin Combined 

(tons per day) 

 VOC VOC NOx NOx 

SOURCE CATEGORY 2002 2008 2002 2008 

Light Duty Passenger 216.68 110.71 173.63 84.02 

Light Duty Trucks - 1 36.98 21.49 34.80 18.64 

Light Duty Trucks - 2 74.25 48.79 118.13 66.97 

Medium Duty Trucks 36.72 25.05 60.22 38.38 

Light Heavy Duty Gas Trucks - 1 22.51 12.37 29.96 18.61 

Light Heavy Duty Gas Trucks - 2 3.49 2.27 4.42 3.49 

Medium Heavy Duty Gas Trucks 8.91 4.55 8.98 6.18 

Heavy Heavy Duty Gas Trucks 5.00 3.20 10.71 7.29 

Light Heavy Duty Diesel Trucks - 1 0.02 0.30 0.75 11.71 

Light Heavy Duty Diesel Trucks - 2 0.25 0.28 9.66 9.25 

Medium Heavy Duty Diesel Trucks 1.35 1.28 82.44 62.81 

Heavy Heavy Duty Diesel Trucks 14.71 13.46 174.68 152.12 

Motorcycles 12.57 17.28 2.27 4.23 

Heavy Duty Diesel Urban Buses 0.53 0.48 15.14 13.10 

Heavy Duty Gas Urban Buses 0.59 0.54 0.95 0.84 

School Buses 0.46 0.39 5.38 5.35 

Other Buses 0.82 0.61 4.50 4.16 

Motor Homes 1.82 1.00 5.29 3.99 

Onroad Subtotal 437.64 264.04 741.89 511.13 

Aircraft 9.61 11.41 18.28 23.02 

Trains 2.58 2.55 39.29 30.21 

Ships And Commercial Boats 5.54 5.44 93.11 108.04 

Recreational Boats 87.05 78.51 16.41 23.75 

Off-Road Recreational Vehicles 9.83 11.98 0.30 0.24 

Off-Road Equipment 127.08 107.71 285.41 229.89 

Farm Equipment 3.25 2.52 15.75 12.09 

Fuel Storage And Handling 27.96 18.30 0.00 0.00 

Offroad Subtotal 272.89 238.42 468.56 427.26 

Pre-Baseline Emission Reduction Credits Subtotal 0.63 0.22 

Military Growth Increment 2.33 

TOTAL 1099.29 817.96 1310.41 1032.07 

Source: ARB SIP emissions inventory. 

Eight-Hour Ozone Attainment Plan
Attachment B Planned Military Projects Subject to General Conformity 

B-1 

ATTACHMENT B 

PLANNED MILITARY PROJECTS SUBJECT TO GENERAL CONFORMITY 

Table 1. Projected Emissions and Preliminary Schedule for Placement of 

Littoral Combat Ships

Table 2. Projected Emissions and Preliminary Schedule for Marine Corps 

Projects through 2015

Source: Letters to Air Pollution Control District from the Department of the Navy and from the Marine Corps, 

dated January 4 and January 5, 2007, respectively. 

Eight-Hour Ozone Attainment Plan
Attachment C Pre-Baseline Banked Emission Credits 

C-1 

ATTACHMENT C 

PRE-BASELINE BANKED EMISSION CREDITS 

Table C-1 

San Diego APCD ERC Banking Registry Summary 

Emission Reduction Credits Issued in 2002 and Earlier 

 Certificate NOx VOC Cumulative Totals 

Company Name Number (TPY) (TPY) NOx VOC 

Carpenter Special Products Corporation 973125-01 7.2 0.00 7.20 

Caspian, Inc. 890712-07 16.90 0.00 24.10 

City of San Diego, Metropolitan Wastewater Dept. 950766-06 0.38 0.00 24.48 

 970821-02 22.76 0.00 47.24 

General Dynamics Properties, Inc. 970809-02 1.26 1.26 47.24 

 970809-05 0.23 1.26 47.47 

Hughes-Aircraft Co., Electro-Opti Cal Systems 940261-01 1.06 1.26 48.53 

 940261-02 0.22 1.26 48.75 

Muht-Hei, Inc. 981002-01 0.18 1.26 48.93 

 981002-02 0.18 1.26 49.11 

 981002-03 0.18 1.26 49.29 

 981002-04 0.18 1.26 49.47 

 981002-05 0.57 1.26 50.04 

 981002-06 0.19 1.26 50.23 

 981002-07 2.23 1.26 52.46 

 981002-08 1.28 1.26 53.74 

 981002-09 0.18 1.26 53.92 

 981002-10 2.07 1.26 55.99 

 981002-11 1.28 1.26 57.27 

 981002-12 0.57 1.26 57.84 

National Steel & Shipbuilding 40995-02 0.18 1.44 57.84 

 40995-03 0.60 1.44 58.44 

 40996-02 0.04 1.48 58.44 

 40997-02 0.32 1.80 58.44 

 40997-03 0.02 1.80 58.46 

Naval Air Station, North Island 991014-01 8.00 9.80 58.46 

 991015-01 3.30 13.10 58.46 

 991016-01 18.70 31.80 58.46 

Naval Station, San Diego 950949-01 4.83 36.63 58.46 

 940206-01 0.67 37.30 58.46 

 940206-03 0.05 37.30 58.51 

Navy Region Southwest 990223-01 12.02 49.32 58.51 

Northrop-Grumman Ryan Aeronautical Center 975000-01 1.20 49.32 59.71 

Otay Mesa Generating Co., LLC 990902-01 1.21 50.53 59.71 

 991123-01 17.05 50.53 76.76 

 000128-01 25.00 50.53 101.76 

 000427-01 1.30 51.83 101.76 

 000427-02 30.10 51.83 131.86 

 000918-01 10.30 51.83 142.16 

 000224-01 4.40 56.23 142.16 

 010629-01 0.32 56.55 142.16 

 010629-02 2.39 58.94 142.16 

Eight-Hour Ozone Attainment Plan
Attachment C Pre-Baseline Banked Emission Credits 

C-2 

Table C-1 continued 

San Diego APCD ERC Banking Registry Summary 

Emission Reduction Credits Issued in 2002 and Earlier 

 Certificate NOx VOC Cumulative Totals 

Company Name Number (TPY) (TPY) NOx VOC 

PGET 020906-01 20.70 58.94 162.86 

Rohr, Inc., a subsidiary of BFGoodrich Co. 972754-01 5.30 58.94 168.16 

Sempra Energy Resources 020620-02 0.40 58.94 168.56 

Solar Turbines 970123-04 10.00 68.94 168.56 

 950562-01 0.60 68.94 169.16 

Sony Electronics, Inc. 940652-01 0.54 68.94 169.70 

 977590-01 2.90 68.94 172.60 

Sony Electronics, Inc. 977589-08 0.30 68.94 172.90 

 977589-09 2.20 71.14 172.90 

 977589-02 1.90 73.04 172.90 

 977589-04 0.10 73.04 173.00 

Southern California Edison Company 950171-01 0.51 73.55 173.00 

 950171-03 0.02 73.55 173.02 

Surface Technologies 990325-01 1.48 73.55 174.50 

United States Marine Corps 030507-01 3.00 76.55 174.50 

US Foam 974375-03 0.10 76.55 174.60 

SW Division, Naval Facilities Engineering Cmd. 954185-01 2.00 76.55 176.60 

 960709-01 9.00 76.55 185.60 

 970311-01 13.00 76.55 198.60 

 980511-03 3.15 76.55 201.75 

 980521-02 13.25 76.55 215.00 

 980529-02 7.40 76.55 222.40 

Unisys Corporation 901238-01 3.66 76.55 226.06 

 921410-01 1.25 76.55 227.31 

 940577-01 2.95 76.55 230.26 

USN Communications Station 940560-01 2.40 78.95 230.26 

 940560-04 0.05 78.95 230.31 

 940561-01 0.12 79.07 230.31 

 940561-03 0.00 79.07 230.31 

 940562-01 0.12 79.19 230.31 

 940562-03 0.00 79.19 230.31 

TOTALS (tons/year) = 79.19 230.31 

Eight-Hour Ozone Attainment Plan
Attachment D Analysis of Potential Additional Stationary Source Control Measurements 

D-1 

ATTACHMENT D 

ANALYSES OF POTENTIAL ADDITIONAL STATIONARY SOURCE 

CONTROL MEASURES 

D.1 Low VOC Solvent Cleaning 

Existing Rule 67.6 (Solvent Cleaning Operations) addresses VOC emissions generated by the 

application of solvents (held in a tank or reservoir) to remove unwanted materials, such as dirt 

and oils, from a surface. SCAQMD Rule 1122 is more stringent and contains the following 

requirements that are not in District Rule 67.6: 

• Solvent VOC limit of 25 grams per liter for cold cleaners, including remote reservoirs 

and open-top dip tanks; or airless or air-tight cleaning systems for cold cleaners using 

high-VOC solvents; 

• freeboard ratio of 0.75 for all open-top dip tanks; 

• requirement for a superheated vapor system or secondary freeboard chiller for open-top 

vapor degreasers; 

• freeboard ratio of 1.0 for all open-top vapor degreasers; and 

• automated parts handler. 

Several other air districts have adopted and implemented similar control measures, but with a 

VOC content limit of 50 grams per liter. These and other potential control requirements were 

evaluated to determine their technological feasibility, potential VOC reductions, and costeffectiveness for San Diego County sources. 

The cost-effectiveness of water-based or low-VOC cleaning systems is primarily affected by the 

VOC emission rate of the unit being replaced and the increased electricity needed to heat and 

pump aqueous solvents in the new replacement unit. Over 86% of the approximately 5,100 

degreasing units in San Diego are small remote reservoirs with VOC emissions of less than 

0.324 pounds per day, or 118 pounds per year, each. The lowest and average cost-effectiveness 

values calculated for these units were $4.36 and $5.26, respectively, per pound of VOC reduced. 

The Low VOC Solvent Cleaning control measure has taken longer to develop than other control 

measures. Rule 67.6, which was initially adopted in 1979, needed to be substantially rewritten 

and was split into two rules, one addressing cold solvent cleaners and the other addressing vapor 

degreasers. Most importantly, due to the large number of small businesses affected by the rule, 

the public input process for this rule development needed to be extensive. The new replacement 

Rules 67.6.1 (Cold Solvent Cleaning and Stripping Operations) and 67.6.2 (Vapor Degreasing 

Operations), are being adopted simultaneously with this 8-Hour Ozone Attainment Plan. 

New Rule 67.6.1 will require that each solvent utilized in a cold solvent cleaning operation must 

have a VOC content of 50 grams per liter of material or less, in addition to other requirements. 

New Rule 67.6.2 will apply to vapor degreasing operations, and the requirements are generally 

identical to those in current Rule 67.6, because more stringent requirements on vapor degreasers 

would have only negligible emissions reductions. When new Rule 67.6.1 is implemented in 

2008, San Diego County cold solvent cleaning VOC emissions are projected to be reduced by 

about 1 ton per day, relative to the 2002 baseline. Although these emissions reductions are not 

Eight-Hour Ozone Attainment Plan
Attachment D Analysis of Potential Additional Stationary Source Control Measurements 

D-2 

available in time to advance the attainment year to 2007, they will assist in reducing ozone 

concentrations in 2008 to the level of the national 8-hour ozone standard. 

D.2 Further Control of Architectural Coatings 

Following the District adoption of the existing version of the Architectural Coatings Rule 67.0 

(discussed in Section 3.2.2), the South Coast Air Quality Management District (SCAQMD) 

amended its Rule 1113 in 2006 to further tighten VOC content limits for Architectural Coatings 

in years 2007 and 2008. Adopting similar limits in San Diego County could potentially reduce 

VOC emissions from Architectural Coatings by an estimated 50% or approximately 5 tons per 

day, based on very preliminary ARB estimates. 

ARB is updating its estimates of Architectural Coatings emissions based on a new 2005 survey 

of architectural coating products sold in California during 2004. Further, ARB is developing a 

statewide Suggested Control Measure (SCM)1 that will be similar, but not necessarily identical, 

to SCAQMD Rule 1113. ARB intends to adopt the Architectural Coatings SCM in September 

2007, with local rule adoption and compliance anticipated in 2009. Consequently, the 

anticipated additional emission reductions are not available in time to advance San Diego 

County’s eight-hour ozone attainment year to 2007. 

D.3 Automotive Refinishing 

This source category is regulated by District Rule 67.20 (Motor Vehicle and Mobile Equipment 

Refinishing Operations). Total VOC emissions from the more than 400 facilities in this source 

category are an estimated 275 tons per year, based on the 1996 rule development emission 

inventory and projected emission reductions from rule adoption. 

ARB adopted an SCM for Automotive Coatings on October 20, 2005. This measure has more 

stringent future VOC limits in several coating categories than Rule 67.20. These more stringent 

limits will likely result in the use of waterborne coatings for many topcoats, which have 

additional equipment surface preparation and application requirements compared to existing 

solvent-borne topcoats used in this industry, which is comprised mostly of small businesses. 

This SCM has since been adopted by at least two California air districts. If adopted by the 

District, this control measure could potentially result in an estimated VOC emission reduction of 

an 0.6 ton per day. However, based on evaluation of the future availability of compliant coatings 

in California as a whole, and considering the equipment upgrades and training necessary to use 

these compliant coatings, the recommended compliance date in the SCM is not until January 1, 

2009, or 2010 for some coating categories. The most recently adopted California air district rule 

based on the SCM—San Joaquin Valley Unified Air Pollution Control District (SJVUAPCD) 

Rule 4612 Motor Vehicle And Mobile Equipment Coating Operations, Phase II (September 

2006)—retains these 2009 and 2010 compliance dates. SCAQMD Rule 1151–Motor Vehicle 

and Mobile Equipment Nonassembly Line Coating Operations, which was adopted very shortly 

after the SCM, has a slightly earlier compliance date of July 1, 2008. Regardless, because of the 

limited availability of compliant coatings and the necessary equipment upgrades and operator 

training, adoption of this measure would result in little if any emission reductions before 2008. 

 

1 A Suggested Control Measure (SCM)is a "model rule", developed by ARB for source categories where statewide 

consistency in control requirements is particularly desirable, that local air districts can copy for their rules for the 

covered source category. . 

Eight-Hour Ozone Attainment Plan
Attachment D Analysis of Potential Additional Stationary Source Control Measurements 

D-3 

For existing rules with VOC limits already in place, the District compared Rule 67.20 to 

SJVUAPCD Rule 4602 (Motor Vehicle and Mobile Equipment Refinishing Operations). 

SJVUAPCD Rule 4602 has lower VOC limits than Rule 67.20 for this source category in the 

following coating categories: Group I Vehicle primers and primer surfacers, Group II Vehicle 

primers and primer surfacers, and Group II Vehicle primer sealers. Estimated emissions in San 

Diego County from these coating categories comprise a small fraction of total emissions from 

the source category (estimated emissions are less than 11 tons per year from the affected coating 

categories). If SJVUAPCD 4602 limits were incorporated in Rule 67.20 the estimated emission 

reduction potential would be about 6.1 tons per year, or 0.02 tons per day. However, 

SJVUAPCD Rule 4602 allows a higher ratio of high VOC precoat to primer usage than Rule 

67.20 (1 gallon of precoat to 1 gallon of primer as compared to 1 gallon of precoat to 4 gallons of 

primer for Rule 67.20) and higher allowable usage of high VOC specialty coatings (1 gallon per 

day compared to 3 gallons per month for Rule 67.20). Therefore the overall emission reductions 

achieved by Rule 67.20 may be equivalent or greater than SJVUAPCD Rule 4602. 

D.4 Adhesive and Sealant Applications

This source category is regulated by District Rule 67.21 (Adhesive Material Application 

Operations). Potential emission reductions were estimated by comparison with South Coast 

Rule 1168 (Adhesive and Sealant Applications), which has more stringent VOC content limits 

than Rule 67.21 in several adhesive categories. Total VOC emissions in San Diego County from 

this category are estimated at approximately 1302 tons per year, based on the 1998 Rule 67.21 

rule development emission inventory and projected emission reductions from adoption of Rule 

67.21 in 1998. Nearly all of the emissions (1249 tons per year) and potential emission 

reductions (512 tons per year, or 1.4 tons per day) that would be affected by adoption of Rule 

1168 requirements are from nonpermitted sources such as construction operations. Although the 

estimated emission reductions are relatively large, the estimate does not account for penetration 

of the current San Diego market by low VOC adhesives sold in South Coast. Information from 

adhesive suppliers indicates that they typically provide all of Southern California with the same 

products. Emission reductions from permitted sources are not anticipated to be significant (total 

estimated emissions are only 53 tons per year). This category will be given a high priority for 

evaluation for future rule development, especially with regards to refining the emission 

inventory and assessing availability of low VOC adhesives. 

D.5 Solvent Wipe Cleaning Operations 

Solvent wipe cleaning (also called surface preparation or solvent cleaning) is defined in Rule 

67.6 (Solvent Cleaning Operations) and similar rules in other California air districts as a method 

of cleaning a surface by physically rubbing it with a material such as a rag wetted with a solvent. 

This source category does not include the cleaning of coating application equipment, which has 

separate standards. It also does not include cleaning of parts in tanks or basins regulated by Rule 

67.6. Further VOC reductions under Rule 67.6 are currently being evaluated. 

Presently there are a variety of solvents used in San Diego County for cleaning and preparing 

surfaces for painting or for general maintenance cleaning. These solvents include isopropyl 

alcohol (IPA), methyl ethyl ketone (MEK), mineral spirits, xylene, lacquer thinner, etc. The 

VOC content of surface preparation and cleaning solvents are regulated under the District's 

source-specific coating Rules 67.3 (metal parts and products), 67.4 (can and coil), 67.5 (paper, 

film, and fabric), 67.9 (aerospace), 67.11 (wood), 67.12 (polyester resin), 67.18 (marine coating), 

Eight-Hour Ozone Attainment Plan
Attachment D Analysis of Potential Additional Stationary Source Control Measurements 

D-4 

67.20 (automotive refinishing) and 67.21 (adhesives). These rules limit either the VOC content 

or vapor pressure (or boiling point) of solvents used for wipe cleaning operations. Those wipe 

cleaning operations that are not covered by source-specific rules are regulated by Rule 66 

(organic solvents). Rule 66 does not limit the VOC content of solvents. Instead it requires the 

use of add-on control equipment for sources emitting certain quantities of specified organic 

solvents. 

Based on available emission inventory data and, in some cases, engineering permit files, the 

estimated VOC emissions from wipe cleaning operations subject to Rule 66 are about 48 tons per 

year. The estimated VOC emissions from wipe cleaning operations subject to the sourcespecific coating rules are approximately 128 tons per year. The bulk of the emissions from 

operations subject to source-specific coating rules (about 65%) are from marine coating 

operations (67.18). Some coating operations such as can and coil coating (Rule 67.4), paper, 

fabric and film coating (Rule 67.5), and adhesive material application operations (Rule 67.21) do 

not use significant amounts of cleaning solvents containing VOCs. In addition, emissions from 

aerospace coating operations (Rule 67.9) are not included in the total. Aerospace coating 

operations are specifically exempt from general wipe cleaning solvent limits in the rules of other 

districts and the standards for wipe-cleaning in District Rule 67.9 are consistent with the limits in 

South Coast Rule 1124 (Aerospace Assembly and Component Manufacturing Operations) for 

aerospace coating operations. 

The total estimated VOC emissions from wipe cleaning operations are about 177 tons per year. 

The estimated potential emission reductions for this source category are about 142 tons per year, 

or 0.57 tons per day, based on requiring use of wipe cleaning solvents with a VOC content of 50 

grams per liter or less. This would be consistent with the standards for this source category in 

rules of several other air districts. This category will be given a high priority to be investigated 

for future rule development. 

D.6 Wood Products Coating Operations 

This source category is regulated by District Rules 67.11 (Wood Products Coating Operations) 

and 67.11.1 (Large Coating Operations For Wood Products). Rule 67.11 applies to all sources 

while Rule 67.11.1 only applies to sources emitting more than 25 tons per year of VOCs. Rule 

67.11 contains technology forcing VOC content limits for wood coatings. Although the District 

is currently reviewing their feasibility, these limits were scheduled to be implemented July 1, 

2005. Based on emission inventory information, total estimated VOC emissions from this source 

category are about 335 tons per year of which 12 tons per year are from sources exempt from 

Rule 67.11. If successful, the projected emission reductions from implementation of the 2005 

VOC limits are about 112 tons per year from current emission levels. 

South Coast Rule 1136 (Wood Products Coatings) regulates this source category and has lower 

technology forcing VOC content limits than those in Rule 67.11 in several coating categories. 

These technology forcing limits were to be implemented on July 1, 2005, and affect the 

following coating categories: conversion varnishes, fillers, high-solid stains, sealers and lowsolids stains, toners or washcoats. If the lower limits in South Coast Rule 1136 were 

incorporated in Rule 67.11, the potential emission reductions are estimated to be about 57 tons 

per year, over and above the projected emission reductions from the technology forcing 2005 

limits already in Rule 67.11. 

Eight-Hour Ozone Attainment Plan
Attachment D Analysis of Potential Additional Stationary Source Control Measurements 

D-5 

In addition, South Coast Rule 1136 limits rule applicability to those sources using more than one 

gallon per day of wood coating while Rule 67.11 limits rule applicability to those sources using 

500 gallons per year or more of wood coatings. If the applicability limit in Rule 67.11 were 

reduced to the South Coast Rule 1136 limit, which was assumed to be equivalent to an annual 

limit of 125 gallons per year, the estimated potential emission reductions would be 5.6 tons per 

year. Thus, the total estimated potential emission reductions would be 63 tons per year, or 0.25 

tons per day. 

The District anticipates that an evaluation of the effect of the mid-2005 limits can be made in 

2007. This allows for the use of coatings complying with the mid-2005 standards in Rule 67.11 

and South Coast Rule 1136 for one full calendar year. 

D.7 Graphic Arts 

This source category is regulated by District Rule 67.16 (Graphic Arts Operations). Based on 

emission inventory information, total estimated VOC emissions from this source category are 

about 82 tons per year. The emissions result from printing processes or related coating 

processes. 

South Coast Rule 1130 (Graphic Arts) has lower VOC limits than Rule 67.16 for this source 

category for fountain solutions. In addition, South Coast Rule 1171 (Solvent Cleaning 

Operations) has lower VOC limits than Rule 67.16 for cleaning ink application equipment for 

roller washes and general ink cleaning. If the South Coast Rule 1130 and Rule 1171 VOC limits 

were incorporated in Rule 67.16, the estimated potential VOC emission reductions would be 

about 57 tons per year, or 0.23 tons per day. Nearly all (about 98%) of the emission reductions 

would result from reducing the VOC content of cleaning materials. This assumes that the lower 

VOC content cleaning materials are as effective as the current cleaning materials and that 

increased usage is not required. Both South Coast Rules 1130 and 1171 also have lower VOC 

limits than Rule 67.16 in several specialty ink or solvent cleaning categories (for example, 

flexographic ink on porous substrates and flexographic printing cleanup) and for adhesives. 

However, none of these materials have been identified as being used in San Diego County for 

this source category. 

The District is assigning this category a medium priority for evaluation for future rule 

development, including estimating cost effectiveness and feasibility of more stringent standards. 

Because nearly all the emission reductions result from cleaning materials, the District may 

consider those changes as part of possible rule making for the wipe-cleaning source category. 

D.8 High Emitting Spray Booth Facilities 

South Coast Rule 1132 (Further Control of VOC Emissions from High-Emitting Spray Booth 

Facilities) applies to spray booths emitting more than 20 tons per year of VOCs. This rule 

requires a further 65% VOC emissions reduction from these operations beyond that required by 

South Coast coating VOC content rules. The District currently has no comparable rule. The 

District emission inventory information indicates that there may be five operations in San Diego 

for which VOC emissions from one spray booth (or a combination of spray booths) exceed 20 

tons per year. However, four of these are wood coating operations and the estimated emission 

reductions resulting from implementation of Rule 67.11’s technology forcing VOC content 

limits for wood coating operations that took effect July 1, 2005, would bring three of these 

operations well below the 20 ton per year threshold. Emissions from the remaining two facilities 

Eight-Hour Ozone Attainment Plan
Attachment D Analysis of Potential Additional Stationary Source Control Measurements 

D-6 

(after adjustment for projected Rule 67.11 reductions in 2005) are about 59 tons per year 

combined, and the estimated emissions reduction potential is about 39 tons per year, or 0.15 tons 

per day (65% additional control). 

The District views this as a low to medium priority measure because more than half the 

emissions from the remaining two facilities are from one large wood coating operation. These 

wood coating emissions may be reduced more than projected by the technology forcing 2005 

limits in Rule 67.11. Therefore, emission reductions from add-on controls may be significantly 

less than the projected 39 tons per year. The District is currently evaluating the feasibility of the 

Rule 67.11 technology forcing limits. If it is determined that some or all of the limits are not 

feasible or if the residual emissions warrant further control, the District will reevaluate the 

priority of this measure. 

D.9 Equipment Leaks 

Bay Area AQMD's Rule 8-18 (Equipment Leaks) establishes vapor and liquid leak standards to 

reduce emissions of volatile organic compounds from leaking equipment at refineries, bulk 

terminals, bulk plants and chemical plants. It exempts facilities with fewer than 100 valves or 

fewer than 10 pumps and compressors (Rule 8-22, Valves and Flanges at Chemical Plants, 

applies in these cases). It also exempts equipment handling organic liquids having initial boiling 

points above 302o F. It does not apply to connections between the loading racks at bulk 

terminals and bulk plants and the vehicle (mobile transports) being loaded. It sets inspection 

frequency criteria (daily visual, quarterly instrument checks for most components), repair 

requirements, and leak standards – 3 drops per minute for liquid leaks, 100 parts per million by 

volume (ppmv) as methane for most vapor leaks, and 500 ppmv as methane for pumps, 

compressors and pressure relief devices. 

The Rule 8-18 definition of Chemical Plants includes any facility engaged in producing organic 

or inorganic chemicals or the manufacturing of products by chemical processes and having "325" 

as the first three digits in the applicable North American Industry Classification code. This code 

applies to dozens of facilities in San Diego County but likely few would have 100 or more valves 

or 10 or more pumps or compressors in VOC service. San Diego has no petroleum refineries 

that would be subject to such a rule. Possibly, a rule such as Rule 8-18 could apply to the major 

gasoline bulk terminals, some of the bulk plants, and two kelp-processing facilities. However, a 

valve, pump and compressor count would be needed to determine if the rule would apply to 

facilities in San Diego. 

Rule 8-18 establishes the same liquid leak standard (3 drops per minute) as San Diego rules 

applicable to gasoline bulk terminals and bulk plants (Rules 61.1, 61.2 and 61.7), kelp 

processing (Rule 67.10), coating and printing ink manufacturers (Rule 67.19), and 

pharmaceutical and cosmetics manufacturers (Rule 67.15). However, the San Diego rules have a 

more stringent allowable leak repair period than Rule 8-18 (0-3 days versus 7 days). Rule 8-18 

has a more stringent vapor leak standard for equipment at bulk terminals and bulk plants than do 

San Diego Rules 61.1 and 61.2 (100-500 ppmv @1.0 cm versus 1375 ppmv @1.3 cm as 

methane). However, San Diego Rule 61.1 applies to the vapor transfer path including the 

connection to a mobile transport while Bay Area Rule 8-18 specifically exempts such 

connections. Inspectors in San Diego County generally do not find vapor leaks at the bulk 

terminals and bulk plants along the hard-piped components. Typically, if vapor leaks are found, 

Eight-Hour Ozone Attainment Plan
Attachment D Analysis of Potential Additional Stationary Source Control Measurements 

D-7 

it is at the loading rack/mobile transport interface, and from the vapor fittings (e.g. drybreaks) on 

the mobile transport themselves (under ARB jurisdiction). 

More detailed evaluation would be needed to determine the extent to which a rule such as Rule 

8-18 would apply to local chemical plants and whether the standards for fugitive vapor leaks are 

technologically feasible and cost-effective. However, likely emission reductions from bulk 

plants and bulk terminals would be expected to be far less than 10 tons per year. The most 

recent inventory of these sources showed approximately 13 tons per year total VOC emissions 

from loading rack operations, and fugitive vapor and liquid leak emissions from hard-piped 

components, pumps and compressors are likely far less than this amount. As to kelp processing 

facilities, most fugitive vapor emissions are not associated with equipment or piping leaks. 

Lines used to transport VOC/air streams are operated at only a few inches of water gauge 

pressure. 

Based on this initial evaluation, it does not appear that there is a significant emission reduction 

potential and therefore this item should be given a low priority for evaluation for future rule 

development. 

D.10 Petroleum Storage Tanks 

This source category is regulated by District Rule 61.1 (Receiving and Storing Volatile Organic 

Compounds at Bulk Plants and Bulk Terminals), which is applicable to large storage tanks for 

gasoline and other high volatility motor vehicle fuels. Based on emission inventory information 

and updated equipment descriptions, estimated emissions from this source category are about 46 

tons per year. Rule 61.1 has standards for fittings for internal floating roof tanks, external 

floating roof tanks, and fixed roof tanks and requires Best Available Control Technology 

(BACT) for new or replacement rim seals for external and internal floating roof tanks. 

South Coast 1178 (Further Reductions of VOC Emissions from Storage Tanks at Petroleum 

Facilities) has further control measures for this source category. This rule is applicable to above 

ground storage tanks at petroleum facilities emitting more than 20 tons per year of VOCs. The 

rule specifies rim seal types and fittings for external and internal floating roof tanks and fixed 

roof tanks. The rule also requires all external floating roof tanks subject to the rule be domed by 

July 1, 2008. 

San Diego County has two petroleum storage facilities that emit more than 20 tons per year. 

Examination of the existing rim seals and fittings for the storage tanks at these facilities indicates 

that most of the existing seals and fittings at these facilities would meet the standards in South 

Coast Rule 1178. Based on emission factors in the South Coast Rule 1178 staff report, if the 

standards of South Coast Rule 1178 were incorporated in Rule 61.1 the estimated emission 

reduction potential would be about 21 tons per year. About 40% of the emission reduction 

potential (9 tons) would result from upgrading rim seals. However, since BACT is required by 

Rule 61.1 for rim seal replacement, these emission reductions will be achieved over time by 

existing Rule 61.1. The remaining potential emission reduction benefit of the Rule 1178 

standards would be approximately 12 tons per year, or 0.03 tons per day, from the more stringent 

requirements for fittings and the requirement for external floating roof tanks to be domed. Based 

on this initial evaluation, the District does not plan further evaluation for rule development for 

this source category because of the very limited VOC emission reduction potential. 

Eight-Hour Ozone Attainment Plan
Attachment D Analysis of Potential Additional Stationary Source Control Measurements 

D-8 

D.11 Mobile Transport Tanks Loading 

This source category is regulated by District Rule 61.2 (Transfer of Organic Compounds into 

Mobile Transport Tanks). Rule 61.2 controls vapors displaced by loading of mobile transport 

tanks with gasoline and other high volatility fuels from bulk terminals and vapor and liquid leaks 

during the loading process. The primary standard of Rule 61.2 requires a 90% emission 

reduction for all VOC vapors displaced during the transport tank loading process. Based on 

emission inventory information, total estimated VOC emissions in San Diego County due to 

vapor displacement are about 13 tons per year from four bulk terminal loading rack facilities. 

San Joaquin Valley Rule 4621 (Gasoline Transfer into Stationary Storage Containers, Delivery 

Vessels and Bulk Plants) requires a 95% emission reduction for displaced VOC vapors. Source 

testing data for the largest San Diego facility shows that it consistently achieves greater than 

99% control of VOC vapors released in the loading process. The estimated emission reduction 

potential for the three remaining facilities is about 6.4 tons per year, or 0.02 tons per day, if they 

were required to meet a 95% control level instead of the 90% control level in existing Rule 61.2. 

Based on this initial evaluation, the District does not plan further evaluation for rule 

development for this source category at this time because of the very limited VOC emission 

reduction potential. 

D.12 Food Products Manufacturing/Processing 

This source category is regulated by South Coast Rule 1131 (Food Product Manufacturing and 

Processing Operations), which requires use of solvents with less than 120 grams per liter VOC or 

an 85% emission reduction for nonsterilization operations (emission reductions of about 75% are 

required for sterilization operations). The staff report for South Coast's Rule 1131 indicates that 

the two solvents most often used for processing operations and sterilization processes in the food 

industry are hexane and IPA. Based on AB 2588 Hot Spots program information, total solvent 

use in San Diego County for facilities that manufacture or process food products is about 0.06 

tons per year for hexane and 80 tons per year for IPA. However, more than 90% of these IPA 

emissions are from two kelp-processing facilities already regulated by District Rule 67.10 (Kelp 

Processing and Bio-Polymer Manufacturing Operations). Under Rule 67.10, the kelp processing 

facilities have reduced their VOC emissions more than 90%. If a rule incorporating South Coast 

standards for VOC emissions for food processing facilities were adopted, estimated potential 

VOC emission reductions from the remaining unregulated IPA emissions would be about 5.9 

tons per year, or 0.02 tons per day. Based on this initial evaluation, the District does not plan 

further evaluation for rule development for this source category at this time because of the very 

limited VOC emission reduction potential. 

D.13 Polyester Resins Operations 

This source category is regulated by District Rule 67.12 (Polyester Resin Operations). Based on 

emission inventory information, total estimated VOC emissions for this source category are 79 

tons per year from resins and gel coats. 

South Coast Rule 1162 (Polyester Resins Operations) has slightly lower monomer content limits 

than Rule 67.12 for some resins and gel coats. If the South Coast monomer content limits were 

adopted the estimated potential emission reduction would be about 5.7 tons per year, or 0.02 tons 

per day, for resins and gel coats combined. Based on this initial evaluation, the District does not 

plan further evaluation for rule development for this source category at this time because of the 

very limited VOC emission reduction potential. 

Eight-Hour Ozone Attainment Plan
Attachment D Analysis of Potential Additional Stationary Source Control Measurements 

D-9 

D.14 Aerospace Manufacturing Operations 

Emissions in this category have greatly declined in San Diego County since 1990 due to 

implementation of District Rule 67.9 (Aerospace Coating Operations), the decline in government 

funding for aerospace operations and, in particular, the closing of one large facility. Based on 

emission inventory information, total VOC emissions from this source category are only 35 tons 

per year. 

South Coast Rule 1124 (Aerospace Assembly and Component Manufacturing Operations) has 

lower VOC limits in several coating categories: adhesive bonding primers, antichafe coatings, 

dry lubricative materials (nonfastener), form release coatings, fuel tank coatings, and sealants. 

In addition, South Coast Rule 1124 has a lower VOC limit for paint strippers. Total estimated 

VOC emissions in San Diego for materials in these coating categories and for strippers that 

exceed the limits in South Coast Rule 1124 are less than two tons per year. Emission reductions 

have not been estimated but would be less than two tons per year, or less than 0.01 ton per day. 

Based on this initial evaluation, the District does not plan further evaluation for rule 

development for this source category at this time because of the very limited VOC emission 

reduction potential. 

D.15 Further Control of Industrial and Commercial Boilers, Process Heaters, 

 and Steam Generators 

Rule 69.2 (Industrial and Commercial Boilers, Process Heaters and Steam Generators) regulates 

NOx emissions from boilers with rated heat inputs of 5 million (MM) BTU per hour or more. 

Currently, Rule 69.2 exempts from NOx emission standards any unit with an annual heat input of 

less than 220,000 therms (for units with a heat input rating of less than or equal to 50 MMBTU 

per hour). These units are subject only to operational standards, such as unit maintenance, 

recordkeeping, and an annual boiler tune-up to minimize NOx emissions to the extent feasible. 

Facilities with annual heat inputs of 220,000 therms or more (or greater than 10% capacity factor 

for units with heat input ratings greater than 50 MMBtu per hour) must comply with NOx 

emission standards of 30 ppmv for gas-fired units and 40 ppmv for oil-fired units. Estimated 

NOx emissions from this source category are about 69 tons per year with over 99% of the 

emissions from gas-fired units. 

The District has evaluated the feasibility, cost-effectiveness and emissions reduction potential of 

amending Rule 69.2 to lower the exemption level to 90,000 therms per year (consistent with 

ARB's Reasonably Available Control Technology/Best Available Retrofit Control Technology 

(RACT/BARCT) Guidance Document for boilers), to determine whether the resulting emission 

reductions would be cost-effective. The District also evaluated the local feasibility of more 

stringent emission limits in SJVUAPCD Rule 4306. 

The additional analyses have been conducted. To determine local feasibility of these measures, 

the District evaluated the cost-effectiveness for the following three cases for gas-fired boilers: 

1. Lower Exemption Threshold/Retain Existing Emission Standards. Require that all 

boilers with annual heat input between 90,000 and 220,000 therms meet the 30-ppmv 

NOx standard of existing Rule 69.2, and retain the existing 30-ppmv NOx standard for 

higher usage boilers. This measure would apply to about 40 units with annual heat input 

Eight-Hour Ozone Attainment Plan
Attachment D Analysis of Potential Additional Stationary Source Control Measurements 

D-10 

between 90,000 and 220,000 therms, requiring installation of low NOx burners and/or 

flue gas recirculation to meet the 30-ppmv NOx standard. 

2. Lower Exemption Threshold/Tighten Emission Standards. Require that all boilers with 

annual heat input of 90,000 therms or more meet more stringent standards of 15 ppmv 

NOx for units rated at less than or equal to 20 MMBtu per hour heat input, and 9 ppmv 

NOx for units rated at greater than 20 MMBtu per hour heat input. These NOx standards 

are consistent with those for San Joaquin Valley Rule 4306, adopted on September 18, 

2003. This measure would require about 110 units with annual heat input of 90,000 

therms or more to install emission controls such as ultra-low NOx burners and flue gas 

recirculation to meet the more stringent limits. 

3. Retain Existing Exemption Threshold/Tighten Emission Standards. Require that boilers 

with annual heat input of 220,000 therms or more meet the more stringent (15 ppmv / 9 

ppmv) NOx standards. Units with annual heat input rates of less than 220,000 therms 

would remain subject to the current exemption. This measure would require only the 

approximately 70 units with annual heat input of 220,000 therms or more to install 

additional or replacement emission controls to meet the more stringent limits. 

For each case, cost-effectiveness values were estimated for each affected boiler. The potential 

emission reductions (averaged over 365 days of operation per year) and overall costeffectiveness values for each of the three cases are summarized in Table D-1. 

Table D-1 

Overall Cost-Effectiveness 

Case 

Potential NOx 

Emission Reductions (tons/day) 

Overall CostEffectiveness 

($/lb NOx reduced) 

1 0.03 12 

2 0.10 24 

3 0.05 18 

For all three cases, the estimated overall cost-effectiveness significantly exceeds (by 100% to 

300%) the District’s rule development cost-effectiveness reference level of $6 per pound of NOx 

emission reductions for BARCT for small sources. An investigation of whether there is any 

subset of units for which further controls would be cost-effective determined that none of the 

further control measures were cost-effective for any individual boiler. Based on the poor costeffectiveness and small emission-reduction potential, none of these further control measure 

combinations are feasible and therefore none will be further considered at this time. 

Eight-Hour Ozone Attainment Plan
Attachment D Analysis of Potential Additional Stationary Source Control Measurements 

D-11 

D.16 Small Boilers and Large Commercial Water Heaters 

SCAQMD Rule 1146.1 controls NOx emissions from Small Boilers with rated heat inputs 

between 2 MMBtu per hour to 5 MMBTU per hour. SCAQMD Rule 1146.2 controls NOx 

emissions from large commercial water heaters 75,000 BTU per hour to 2 MMBTU per hour. 

The District is developing a rule to control NOx emissions from small boilers and large 

commercial water heaters with rated heat inputs between 1 MMBtu per hour to 5 MMBTU per 

hour, provided additional analyses during rule development show these measures to be feasible 

based on technology availability, emission reduction potential, and cost-effectiveness. 

Control requirements can take three general forms, 1) requiring installation of retrofit control 

equipment, 2) requiring early replacement of existing units with new controlled units, or 3) 

focusing control requirements only on new units, and allowing new controlled units to gradually 

replace existing units, year after year, at the end of each existing unit’s 25 years useful life. The 

ultimate emissions reduction potential is the same for all three options. The advantage of the 

first two options is that the emissions reductions can be required to occur within a relatively 

short time period (about 2 years), whereas with the third option, the emissions reductions 

accumulate gradually over 25 years. However, the first two options are considerably more 

costly. 

Control feasibility and cost investigations concluded that requiring retrofitting or early 

replacement would not be cost-effective for existing boilers in the 1 – 5 MMBtu per hour size 

range. The estimated average cost-effectiveness to retrofit a 5 MMBtu per hour boiler with lowNOx burners is approximately $10 per pound of NOx reduced, which substantially exceeds the 

District’s standard rule development cost-effectiveness threshold of $6 per pound. The costeffectiveness becomes increasingly unfavorable with decreasing boiler size, reaching 

approximately $30 per pound for a 1 MMBtu per hour boiler. 

An option was considered to require retrofits for only the few largest of the small boilers, for 

which cost-effectiveness would be the least unfavorable. However, that option would yield NOx 

emission reductions estimated to be only 0.08 ton per day, and some of those emission 

reductions will likely be achieved even without a retrofit requirement, through market 

penetration of low-NOx boilers in this size range. Consequently, a retrofit requirement for 

existing small boilers will not be further pursued at this time. 

The cost-effectiveness of requiring immediate replacement of small boilers with new low-NOx 

boilers is even more unfavorable. Consequently, a replacement requirement for small boilers 

will not be further pursued at this time. 

However, requiring low-NOx burners on new small boilers may be feasible, providing emission 

reductions when existing small boilers are replaced at the end of their useful life. New Rule 

69.2.1 is under development to address this boiler size range that, as currently conceived, would 

require all new boilers meet a NOx limit of 30 ppmv. Upon full implementation, which would 

be after all current boilers are replaced at the end of their estimated 25 year average useful 

lifetimes, this measure would provide an estimated 0.3 ton per day reduction in NOx emissions. 

Eight-Hour Ozone Attainment Plan
Attachment D Analysis of Potential Additional Stationary Source Control Measurements 

D-12 

The District also investigated the feasibility of controlling emissions from Large Commercial 

Water Heaters 75,000 BTU per hour to 1 MMBTU per hour. Standard retrofit low-NOx burners 

have not been developed for this size range, based on information provided by the South Coast 

Air Quality Management District. Consequently, the only possible option is requiring full 

replacement of the units with new low-NOx units. The cost-effectiveness for requiring 

replacement exceeds $16 per pound and therefore is not feasible at this time. The District will 

continue to investigate the cost-effectiveness of controlling NOx emissions for this size range of 

units. 

D.17 Further Control of Residential Water Heaters Smaller Than 75,000 BTU per hour 

Existing District Rule 69.5 (Natural Gas-Fired Water Heaters), adopted in 1998, limits emissions 

from new residential-type water heaters in San Diego County to 40 nanograms per Joule (ng/J) 

of heat output. SCAQMD’s Rule 1121 requires most new water heaters sold in the South Coast 

region on or after January 1, 2006, to meet a 10 ng/J NOx limit. For certain specific kinds and 

sizes of units, the compliance deadline is delayed to 2007 or 2008. 

The District intends to assess the commercial availability in San Diego County, and the costeffectiveness, of units complying with the 10 ng/J emissions limit of SCAQMD’s rule. If 

sufficient complying units are found to be commercially available and cost-effective, then the 

District will schedule amendment of Rule 69.5 to incorporate the 10 ng/J limit for new 

residential water heaters sold in San Diego County. Assuming a ten-year useful life for water 

heaters, it would take ten years after the requirement is adopted and becomes effective for all the 

water heaters in the County to be replaced with units that comply with the tightened standard. 

Tightening the water heater NOx emissions limit from the current 40 ng/J to 10 ng/J has been 

estimated to reduce San Diego County NOx emissions by approximately 1.5 tons per day. This 

emission reduction estimate is subject to refinement during future rule development. 

Eight-Hour Ozone Attainment Plan
 Attachment E Calculation of Cumulative Potential Emission Reductions 

 for Possible Reasonably Available Control Measures 

E-1 

ATTACHMENT E 

CALCULATION OF CUMULATIVE POTENTIAL EMISSION REDUCTIONS FOR 

POSSIBLE REASONABLY AVAILABLE CONTROL MEASURES 

Control Measure 

VOC

Emission 

Reduction 

Potential 

(Tons/Day) 

NOx

Emission 

Reduction 

Potential 

(Tons/Day) 

Low VOC Solvent Cleaning 1 

Architectural Coatings 5 

Automotive Refinishing 1 

Adhesive and Sealant Applications 1.4 

Solvent Wipe Cleaning Operations 0.57 

Wood Products Coating Operations 0.25 

Graphic Arts 0.23 

High Emitting Spray Booth Facilities 0.15 

Petroleum Storage Tanks 0.03 

Mobile Transport Tanks Loading 0.02 

Food Products Manufacturing/Processing 0.02 

Polyester Resins Operations 0.02 

Equipment Leaks <0.02 

Aerospace Manufacturing Operations <0.01 

Industrial, Commercial, and Institutional Boilers 0.1 

Small Boilers and Large Commercial Water Heaters 0.3 

Residential Water Heaters 1.5 

Stationary Sources Subtotal 9.7 1.9 

Transportation Control Measures Subtotal 1 2 

Total 10.7 3.9 

Eight-Hour Ozone Attainment Plan
Attachment F Graphical Air Quality Trends Analyses 

F-1 

ATTACHMENT F 

GRAPHICAL AIR QUALITY TRENDS ANALYSES 

Ozone concentrations and the number of ozone exceedances in San Diego County have 

decreased dramatically over the past thirty years. These decreases are attributable to reductions 

in ozone precursor emissions in the San Diego and adjoining air basins (i.e., the South Coast Air 

Basin). Further emissions reductions will lead to further decreases in ozone concentrations in 

San Diego County, resulting in attainment of the 8-hour ozone National Ambient Air Quality 

Standard (NAAQS) by the year 2008. This document uses weight of evidence to illustrate air 

quality improvements in San Diego County and how this rate of progress will continue in future 

years as ozone precursor emissions continue to decrease due to current and future air pollution 

control measures. 

Continuous, hourly ozone concentrations are measured at nine monitoring stations in San Diego 

County. These measurements show that ozone concentrations have been decreasing for the past 

twenty-five plus years as air pollution controls have effectively removed large quantities of 

ozone precursor emissions from the atmosphere. Figure F-1 below shows the number of 

exceedances of the 1-hour NAAQS for ozone and the three-year running average of 1-hour 

exceedances, along with the best-fit linear trend line. As the graph indicates, San Diego County 

attained the 1-hour ozone NAAQS in 2001, a major milestone in the region’s air quality 

improvement. 

Figure F-1 

San Diego Air Basin: Annual Number of 1-Hour 

Federal Ozone Exceedances: 1978 - 2006

0

20

40

60

80

100

1978198119841987199019931996199920022005

Year

Number of 

Exceedances

San Diego Air Basin

3-Year Avg

Linear (3-Year Avg)

Figure F-2 below shows greater detail about when different portions of San Diego County 

attained the 1-hour NAAQS for ozone. This graph shows that since the mid-1990s, attainment of 

the 1-hour ozone standard in San Diego County was achieved in all areas except the Alpine 

monitoring station. This elevated site in the foothills east of metropolitan San Diego is impacted 

by local and transported emissions, keeping ozone concentrations higher than at all other 

monitoring stations in the county. 

Eight-Hour Ozone Attainment Plan
Attachment F Graphical Air Quality Trends Analyses 

F-2 

Figure F-2 

San Diego Monitoring Sites: Days Over 1-Hour 

Federal Ozone Standard: 1978 - 2006

0

20

40

60

80

100

1978198119841987199019931996199920022005

Year

Number of Days

Downtown San Diego

Oceanside

Escondido

Alpine

San Diego Air Basin

The figures above show that the number of exceedances has decreased steadily over the years. 

The graphs also show that although the exceedance trend has been primarily downward, 

perturbations in the downward trend are evident. These occasional upward and downward 

spikes in the overall trend are caused, in part, by changes in weather patterns. Downward spikes 

in the trend are strongly associated with El Niño conditions (warm water anomalies in the 

tropical eastern Pacific Ocean), while upward spikes are likewise associated with La Niña 

conditions (cold water anomalies in the tropical central and eastern Pacific Ocean). Figure F-3 

below illustrates the El Niño/Southern Oscillation (ENSO) pattern for the tropical Pacific Ocean. 

In this figure the positive departures (red) represent El Niño conditions while negative departures 

(blue) represent La Niña conditions. 

Figure F-3 

Eight-Hour Ozone Attainment Plan
Attachment F Graphical Air Quality Trends Analyses 

F-3 

These weather/climate fluctuations are normal and do influence air quality conditions over the 

course of an ozone season. These natural fluctuations are important as they have caused 

perturbations in the otherwise steady downward trend of peak concentrations and ozone 

exceedances. 

Figure F-4 below is provided to show that the decreasing ozone concentrations have eliminated 

smog alerts and Health Advisory episodes. The last Stage II smog alert (0.35 ppm) in San Diego 

County was in 1979, the last Stage I smog episode (0.20 ppm) was in 1991, and the last Health 

Advisory (0.15 ppm) was in 1998. Lower ozone concentrations are decreasing health impacts 

for everyone in San Diego County. 

Figure F-4 

San Diego Air Basin: Stage 1 / Stage 2 Smog Alerts and 

Health Advisories: 1978 - 2006

0

5

10

15

1978198119841987199019931996199920022005

Year

Number of Occurrences

Stage 2 Episodes

Stage 1 Episodes

Health Advisory Episodes

It is important to note that once the occurrence of Health Advisories first hit zero (1996), there 

has been only one Health Advisory after that year. This last Health Advisory was in 1998, a La 

Niña year. Decreasing emissions have since eliminated Health Advisories in San Diego County. 

The 1-hour ozone concentrations shown above were presented to illustrate the ozone trends over 

the past decades. Since the 8-hour ozone standard is written differently than the older 1-hour 

standard, it is more appropriate to look at the actual 8-hour ozone concentrations. As with the 

1-hour ozone standard, the attainment status of San Diego County for the 8-hour ozone standard 

is and has been driven in recent years by the Alpine monitoring station. Figure F-5 below shows 

the four highest 8-hour ozone concentrations measured in San Diego County for the years 1977 

through 2006. This graph shows a general downward trend in peak ozone concentrations, along 

with the up and down spikes associated with climatic conditions. The graph further shows a 

convergence of the four highest values as concentrations have decreased to nearly the attainment 

point. 

Eight-Hour Ozone Attainment Plan
Attachment F Graphical Air Quality Trends Analyses 

F-4 

Figure F-5 

Alpine 8-Hour Ozone: Four Highest Values: 1977 through 2006

0.060

0.080

0.100

0.120

0.140

0.160

0.180

0.200

197719791981198319851987198919911993199519971999200120032005

Year

8-Hr Ozone (ppm)

1st High

2nd High

3rd High

4th High

Standard

Figure F-6 below shows a large decrease in the total number of annual exceedances of the 8-hour 

ozone standard at the Alpine monitoring station. 

Figure F-6 

Alpine 8-Hour Ozone Exceedances: 1991 through 2006

0

10

20

30

40

50

60

Year

Number of Exceedances

No. of Exceedances

3-Year Average

Linear (3-Year Average)

Eight-Hour Ozone Attainment Plan
Attachment F Graphical Air Quality Trends Analyses 

F-5 

Since the 8-hour ozone standard is not written in terms of the numbers of exceedances, it is more 

appropriate to look at the 8-hour Design Value (i.e., three year average of the fourth highest 

concentration). Figure F-7 below shows the annual 4th highest value along with the 8-hour 

design value through 2006. This graph shows a downward trend in both the 4th highest values 

and the design value. This graph shows that San Diego County is nearing attainment of the 

8-hour ozone standard. The upward spike in 2006 will affect the design value for two more 

years. However, the up and down spikes in the historic data suggest that subsequent years will 

trend even further downward. 

Figure F-7 

Alpine 8-Hour Ozone: 4th Annual High and Design Value: 

1977 through 2006

0.060

0.080

0.100

0.120

0.140

0.160

0.180

197719791981198319851987198919911993199519971999200120032005

Year

8-Hr Ozone (ppm)

4th High

Design Value

Standard

Eight-Hour Ozone Attainment Plan
Attachment F Graphical Air Quality Trends Analyses 

F-6 

Figure F-8 below shows the 8-hour design value for the years 1991 through 2006 along with a 

best-fit trend line showing that a linear interpolation during this time period would put the design 

value below the 8-hour standard in 2007. In reality this will not occur due to the slight increase 

in the 4th highest 8-hour concentration in 2006. 

However, past downward trends in 1-hour ozone concentrations show that the decreasing values 

result from decreasing emissions and an isolated year with anomalous weather will not reverse 

the decrease in ozone concentrations or design values (see Section 2.4.3 for additional 

information). 

Figure F-8 

Alpine 8-Hour Ozone: Design Value and Trendline: 1991 

through 2006 (with extrapolations through 2010)

0.070

0.080

0.090

0.100

0.110

0.120

0.130

1991199319951997199920012003200520072009

Year

8-Hour Ozone (ppm)

Design Value

Standard

Linear (Design Value)

Eight-Hour Ozone Attainment Plan
Attachment F Graphical Air Quality Trends Analyses 

F-7 

It is also important to look at average concentrations, not just peak values, to see the 

effectiveness of emission controls on ozone concentrations in San Diego County. Figure F-9 

below shows hourly averaged ozone data from the Alpine monitoring station (ALP) for 1995, 

2000, and 2005. This graph shows that hourly averaged data have steadily decreased over the 

past ten years at this monitoring station, with peak hour concentrations decreasing by 0.009 ppm 

(roughly 1 ppb per year). 

Figure F-9 

ALP: Average Hourly O3 Data for: 1995, 2000 and 2005

0.000

0.010

0.020

0.030

0.040

0.050

0.060

0.070

0 2 4 6 8 10 12 14 16 18 20 22

Hour

O3 (ppm)

1995

2000

2005

Eight-Hour Ozone Attainment Plan
Attachment F Graphical Air Quality Trends Analyses 

F-8 

Figure F-10 below shows the hourly maximum ozone data for the years 1995, 2000, and 2005. 

This graph shows that peak values have fallen significantly at this monitoring station over the 

past ten years (peak values decreased 0.033 ppm between 1995 and 2005), as well as a 

shortening of the length of the “ozone day”. 

Figure F-10 

ALP: Maximum Hourly O3 Data for: 1995, 2000 and 2005

0.000

0.010

0.020

0.030

0.040

0.050

0.060

0.070

0.080

0.090

0.100

0.110

0.120

0.130

0.140

0.150

0.160

0 2 4 6 8 10 12 14 16 18 20 22

Hour

O3 (ppm)

1995

2000

2005

Eight-Hour Ozone Attainment Plan
Attachment F Graphical Air Quality Trends Analyses 

F-9 

Ozone values have decreased in the past as a result of precursor emissions reductions. Figure F11 below shows hourly averaged NO2 data from the Alpine monitoring station (ALP) for 1995, 

2000, and 2005. This graph shows that hourly averaged data have decreased significantly over 

the past ten years at this monitoring station, especially evening and nighttime concentrations 

(i.e., no photochemistry). 

Figure F-11 

ALP: Average Hourly NO2 Data for: 1995, 2000 and 2005

0.000

0.010

0.020

0.030

0 2 4 6 8 10 12 14 16 18 20 22

Hour

NO2 (ppm)

1995

2000

2005

Eight-Hour Ozone Attainment Plan
Attachment F Graphical Air Quality Trends Analyses 

F-10 

This decrease in precursor emissions is also reflected in the decrease in 8-hour ozone 

concentrations at the Alpine monitoring stations. Figure F-12 below shows 8-hour averaged 

ozone data for 1995, 2000, and 2005. This graph shows that average 8-hour concentrations have 

steadily decreased over the past ten years at this monitoring station, with a decrease of 0.007 

ppm between 1995 and 2005. The data suggest that this trend will continue in future years as 

ozone precursor emissions decrease. 

Figure F-12 

ALP: Average Hourly 8-Hr O3 Data for: 1995, 2000 and 2005

0.000

0.010

0.020

0.030

0.040

0.050

0.060

0.070

0 2 4 6 8 10 12 14 16 18 20 22

Hour

8-Hr O3 (ppm)

1995

2000

2005

Eight-Hour Ozone Attainment Plan
Attachment F Graphical Air Quality Trends Analyses 

F-11 

Figure F-13 below shows the hourly maximum 8-hour ozone data for the years 1995, 2000, and 

2005. This graph shows that peak values have fallen significantly (0.034 ppm) at this 

monitoring station over the past ten year, as has the length of the “ozone day”. 

Figure F-13 

ALP: Maximum Hourly 8-Hr O3 Data for: 1995, 2000 and 2005

0.000

0.010

0.020

0.030

0.040

0.050

0.060

0.070

0.080

0.090

0.100

0.110

0.120

0.130

0 2 4 6 8 10 12 14 16 18 20 22

Hour

8-Hr O3 (ppm)

1995

2000

2005

Eight-Hour Ozone Attainment Plan
Attachment F Graphical Air Quality Trends Analyses 

F-12 

As indicated in Figure F-2 above, other regions of the county attained the 1-hour ozone standard 

many years before the Alpine area of the county. Figure X-14 below shows hourly averaged 

ozone data from the Downtown San Diego monitoring station (DTN) for 1995, 2000, and 2005. 

This graph shows that hourly averaged data have markedly decreased over the past ten years at 

this urbanized coastal region monitoring station. 

Figure F-14 

DTN: Average Hourly O3 Data for: 1995, 2000 and 2005

0.000

0.010

0.020

0.030

0.040

0.050

0 2 4 6 8 10 12 14 16 18 20 22

Hour

O3 (ppm)

1995

2000

2005

Eight-Hour Ozone Attainment Plan
Attachment F Graphical Air Quality Trends Analyses 

F-13 

Figure F-15 below shows hourly maximum ozone data from the Downtown San Diego 

monitoring station (DTN) for 1995, 2000, and 2005. This graph shows that hourly maximum 

data have decreased over the past ten years at this monitoring station, as has the length of the 

“ozone day”. 

Figure F-15 

DTN: Maximum Hourly O3 Data for: 1995, 2000 and 2005

0.000

0.010

0.020

0.030

0.040

0.050

0.060

0.070

0.080

0.090

0.100

0.110

0.120

0.130

0.140

0 2 4 6 8 10 12 14 16 18 20 22

Hour

O3 (ppm)

1995

2000

2005

Eight-Hour Ozone Attainment Plan
Attachment F Graphical Air Quality Trends Analyses 

F-14 

Precursor emissions at the Downtown monitoring station have also shown a steady decrease over 

the past ten years. This is shown in Figure F-16 below, with average hourly NO2 data for the 

years 1995, 2000, and 2005. 

Figure F-16 

DTN: Average Hourly NO2 Data for: 1995, 2000 and 2005

0.000

0.010

0.020

0.030

0.040

0 2 4 6 8 10 12 14 16 18 20 22

Hour

NO2 (ppm)

1995

2000

2005

Eight-Hour Ozone Attainment Plan
Attachment F Graphical Air Quality Trends Analyses 

F-15 

Figure F-17 below shows a similar trend for CO at the Downtown monitoring site. Although CO 

is not a significant precursor to atmospheric ozone formation, it can be considered a surrogate 

marker for mobile sources of Volatile Organic Compounds precursor emissions. 

Figure F-17 

DTN: Average Hourly CO Data for: 1995, 2000 and 2005

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

1.1

1.2

1.3

1.4

1.5

1.6

1.7

1.8

0 2 4 6 8 10 12 14 16 18 20 22

Hour

CO (ppm)

1995

2000

2005

Eight-Hour Ozone Attainment Plan
Attachment F Graphical Air Quality Trends Analyses 

F-16 

El Cajon, a major metropolitan area located in an inland valley upwind of the Alpine monitoring 

station also attained the 1-hour ozone standard many years before the Alpine site. Figure F-18 

below shows the hourly averaged ozone data from the El Cajon monitoring station (ECA) for 

1995, 2000, and 2005. This graph shows that hourly averaged data have steadily decreased from 

the higher values measured in 1995, although the 2005 data show a small increase in ozone 

concentrations over 2000. 

Figure F-18 

ECA: Average Hourly O3 Data for: 1995, 2000 and 2005

0.000

0.010

0.020

0.030

0.040

0.050

0.060

0 2 4 6 8 10 12 14 16 18 20 22

Hour

O3 (ppm)

1995

2000

2005

Eight-Hour Ozone Attainment Plan
Attachment F Graphical Air Quality Trends Analyses 

F-17 

However, the maximum hourly concentrations in Figure F-19 below show a decrease over the 

years for this monitoring site, consistent with decreasing peak ozone concentrations throughout 

the county, as well as a shortening of the “ozone day”. 

Figure F-19 

ECA: Maximum Hourly O3 Data for: 1995, 2000 and 2005

0.000

0.010

0.020

0.030

0.040

0.050

0.060

0.070

0.080

0.090

0.100

0.110

0.120

0.130

0.140

0.150

0 2 4 6 8 10 12 14 16 18 20 22

Hour

O3 (ppm)

1995

2000

2005

Eight-Hour Ozone Attainment Plan
Attachment F Graphical Air Quality Trends Analyses 

F-18 

Precursor emissions in this region of the county have also decreased, as evidenced in Figure F-20 

below, which shows hourly NO2 concentrations from the ECA monitoring station. 

Figure F-20 

ECA: Average Hourly NO2 Data for: 1995, 2000 and 2005

0.000

0.010

0.020

0.030

0.040

0 2 4 6 8 10 12 14 16 18 20 22

Hour

NO2 (ppm)

1995

2000

2005

Ozone precursor emissions will continue to decrease over the next several years due to existing, 

ongoing and future control measures. This will result in lower ozone concentrations and lower 

8-hour ozone averages that are predicted to be below the level of the 8-hour ozone NAAQS by 

2008. 

Eight-Hour Ozone Attainment Plan
Attachment G Meteorological Representativeness of Recent Years 

G-1 

ATTACHMENT G 

METEOROLOGICAL REPRESENTATIVENESS OF RECENT YEARS 

G.1 Meteorological Variations 

The relationship between climatic fluctuations and ozone exceedances in San Diego County was 

shown in the previous section. Figure G-1 below shows the annual temperature at Lindbergh 

Field (SAN) in San Diego for the years 1914 through 2006 (preliminary). This figure shows that 

the temperature in San Diego is variable on several time scales (i.e., a few years to decades). 

The 30-year average (typical climatological time scale) shows a rising average, with most of the 

rise occurring between the 1940s and the 1980s. 

The variable nature of climatological conditions in San Diego must be considered when 

evaluating trends in ozone concentrations through the years. This is true for the more recent 

years as well as in the past. 

Figure G-1 

SAN Annual Temperature: 1914 to 2006

58.0

60.0

62.0

64.0

66.0

68.0

1914191919241929193419391944194919541959196419691974197919841989199419992004

Year

Average Temperature (Degrees F)

ANNUAL

30-Yr Avg

Emission reductions over the past several decades have resulted in lower ozone concentrations in 

San Diego County. This has been shown as a reduction in the number of annual exceedances of 

ozone standards and in the design values of ozone concentrations. The relationship between 

climatic variations (e.g., El Niño/La Niña conditions) and ozone exceedances was presented to 

partially explain upward and downward spikes in the otherwise downward trend of annual 

exceedances of ozone standards. The climatic variations in San Diego are a complex mixture of 

temperature, sea surface temperatures, atmospheric circulation patterns (e.g., position and 

Eight-Hour Ozone Attainment Plan
Attachment G Meteorological Representativeness of Recent Years 

G-2 

strength of the Pacific High), and atmospheric stability. The most familiar, and easiest to 

measure and quantify is temperature. 

Figure G-2 below shows plots of 3-year averages (for smoothing) of 8-hour ozone exceedances 

at Alpine and temperatures at SAN for the years 1979 through 2006 (preliminary). This graph 

clearly shows that the 3-year average number of ozone exceedances has been dramatically 

reduced since the early 1990s (from over 100 in 1990 to a minimum of only 4 in 2005). 

Clearly, temperature is not the controlling factor in ozone exceedances in San Diego County, 

although it does play a role in ozone concentrations, and therefore, exceedances as well. 

Emissions reductions are the primary factor in reducing ozone concentrations and the number of 

exceedances. Figure G-2 shows that exceedances dropped precipitously even with stable annual 

average temperatures, and continued decreasing even when annual average temperatures trended 

upwards. 

Figure G-2 

ALP 8-Hour Ozone Exceedances vs. SAN Jun - Aug Average 

Temperature

0

20

40

60

80

100

120

19901991199219931994199519961997199819992000200120022003200420052006

Year

Number of Exceedances

66

68

70

72

74

76

Average Temperature (F)

ALP 3-Yr. Avg. of 8-Hr

Exceedances

SAN 3-Yr. Jun - Aug Avg.

Temp

Eight-Hour Ozone Attainment Plan
Attachment G Meteorological Representativeness of Recent Years 

G-3 

Figure G-3 below shows a more detailed subset of the graph shown above, concentrating on the 

years 1991 through 2006. A linear trend-line based on the number of 8-hour exceedances shows 

the projected date of zero exceedances as being between 2005 and 2006. This has not occurred 

as of this writing. 

Figure G-3 

ALP 4th Highest 8-Hour Ozone Concentrations and 

Exceedances: 1991 through 2006

0.000

0.020

0.040

0.060

0.080

0.100

0.120

1991199219931994199519961997199819992000200120022003200420052006

Year

4th Highest 8-Hour Ozone 

Concentration (ppm)

0

10

20

30

40

50

60

Number of 8-Hour Ozone 

Exceedances

4th High

No. of Exceedances

Linear (No. of Exceedances)

In the following subsections we will discuss the meteorology of three recent years and look at 

how temperature can influence ozone concentrations and exceedances in San Diego. 

G.2 2004 – Clean Year 

2004 represented the first time ever that the Alpine monitoring station measured less than four 

exceedances (only two exceedances, with the fourth highest value of 0.083 ppm) of the 8-hour 

ozone standard (on the road to attainment!). The downward trend in the number of exceedances 

in the figure above indicates that 2004 was a continuation of this trend. The upward trend in 

annual average temperatures during this time period lessens the possibility that 2004 merely an 

anomalous year with no foreseeable repeat occurrence. 

Eight-Hour Ozone Attainment Plan
Attachment G Meteorological Representativeness of Recent Years 

G-4 

Figure G-4 below shows the average monthly temperatures at the Alpine monitoring station for 

the year 2004 versus the 11-year averages for the years 1993 (first available year of 

meteorological data for the Alpine monitoring station) through 2003 (2004 and later years not 

included to reduce effects of autocorrelation). This graph shows that average monthly 

temperatures in 2004 were near the 11-year average during June, July, and September, and 

cooler than normal during August. 

Figure G-4 

ALP 11-Year Average Temperature (1993 through 2003)

 vs. 2004

45.0

50.0

55.0

60.0

65.0

70.0

75.0

80.0

85.0

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

Month

Average Temperature (Degrees F)

11-Year Avg. Temperature

(1993 through 2003)

2004

Eight-Hour Ozone Attainment Plan
Attachment G Meteorological Representativeness of Recent Years 

G-5 

The normal 8-hour ozone season for recent years at San Diego is primarily June through 

September, with June being the month of maximum occurrence, as illustrated in Figure G-5 

below. 

Figure G-5 

ALP Ozone Season: Average Number of 8-Hour Ozone 

Exceedances: 1999 to 2006

0.0

2.0

4.0

6.0

8.0

JANFEBMARAPRMAYJUNJULAUGSEPOCTNOVDEC

Month

Average Number of Exceedances

Average Exceedances (1999

through 2006)

Threshold of One

Eight-Hour Ozone Attainment Plan
Attachment G Meteorological Representativeness of Recent Years 

G-6 

Monthly averaged temperature data for Lindbergh Field (SAN) are also shown in Figure G-6 

below for consistency. The average August temperature was slightly cooler than normal at SAN, 

possibly indicating a deeper marine layer and coastal stratus or extensive high-level cloudiness. 

However, August is typically not the month of maximum ozone exceedances and therefore the 

more typical months of June and July would have had a greater influence on the annual totals. 

Figure G-6 

SAN 30-Year Average Monthly Temperature vs. Indicated Year

50.0

55.0

60.0

65.0

70.0

75.0

80.0

JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC

Month

Average Temperature (Degrees F)

30-Yr Avg

2004

Eight-Hour Ozone Attainment Plan
Attachment G Meteorological Representativeness of Recent Years 

G-7 

Further evidence that 2004 was not an anomalous year climatologically is shown by the cooling 

degree data for San Diego. One cooling degree-day is given for each degree that the daily mean 

temperature departs above the base of 75° F. Figure G-7 below shows the monthly cooling 

degree day averages for the years 1997 through 2003 and the monthly cooling degree values for 

2004. This graph shows that in 2004 the cooling degree day values were near normal in June 

and August and slightly above normal for July and September. Therefore, during the 2004 ozone 

season the cooling degree day values were higher than normal, but not significantly. 

Figure G-7 

Cooling Degree Days - San Diego, California

0

50

100

150

200

250

300

350

400

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

Month

Cooling Degree Days

Average(1997 through 2003)

2004

Climatologically, 2004 was near normal in terms temperature in San Diego. This “clean air” 

year was more the result of decreased emissions in Southern California than anomalous 

climatological conditions. 

Eight-Hour Ozone Attainment Plan
Attachment G Meteorological Representativeness of Recent Years 

G-8 

G.3 2005 – Typical Ozone Year 

The clean air quality year of 2004 was followed by a rather typical ozone year in 2005. There 

were five 8-hour ozone exceedances at Alpine in 2005, versus the 2 measured in 2004, and the 4th

highest concentration was 0.087 (still closing in on attainment). 

Figure G-8 below shows the average monthly temperatures at the Alpine monitoring station for 

the year 2005 versus the 11-year averages for the years 1993 (first available year of 

meteorological data for the Alpine monitoring station) through 2003. This graph shows that 

average monthly temperatures in 2005 were near the 11-year average for all months of the year. 

Figure G-8 

ALP 11-Year Average Temperature (1993 through 2003)

 vs. 2005

45.0

50.0

55.0

60.0

65.0

70.0

75.0

80.0

85.0

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

Month

Average Temperature (Degrees F)

11-Year Avg. Temperature

(1993 through 2003)

2005

Eight-Hour Ozone Attainment Plan
Attachment G Meteorological Representativeness of Recent Years 

G-9 

The monthly averaged temperature data for Lindbergh Field (SAN) are also shown in Figure G-9 

below for consistency (i.e., data from this location show similar pattern, with September and 

October slightly below the 30-year average – although these months are on the tail-end of the 

normal “ozone season”). For the entire year the average temperature at SAN was only 0.9° F 

warmer than the 30-year average. This represents a fairly typical year for San Diego. 

Figure G-9 

SAN 30-Year Average Monthly Temperature vs. Indicated Year

50.0

55.0

60.0

65.0

70.0

75.0

80.0

JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC

Month

Average Temperature (Degrees F)

30-Yr Avg

2005

Eight-Hour Ozone Attainment Plan
Attachment G Meteorological Representativeness of Recent Years 

G-10 

Further evidence that 2005 was a typical year climatologically is shown by the cooling degree 

data for San Diego. Figure G-10 below shows the monthly cooling degree day averages for the 

years 1997 through 2003 and the monthly cooling degree values for 2005. This graph shows that 

in 2005 the cooling degree day values were near normal in June, July, and August and slightly 

below normal for September and October. Therefore, during the 2005 ozone season the cooling 

degree day values were very close to normal. 

Figure G-10 

Cooling Degree Days - San Diego, California

0

50

100

150

200

250

300

350

400

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

Month

Cooling Degree Days

Average(1997 through 2003)

2005

The 4th high 8-hour ozone concentration for 2005 was only 0.002 ppm higher than the standard – 

attainment is in sight! 

G.4 2006 Heat Wave – High Ozone 

In contrast to the years 2004 and 2005, 2006 showed a marked increase in the number of 8-hour 

ozone exceedances in San Diego from previous years (14 in 2006, versus 5 in 2005 and 2 in 

2004), and the measured 8-hour concentrations increased as well (4th highest value in 2006 was 

0.094 ppm, versus 0.087 ppm in 2005, and 0.083 ppm in 2004). 

Warmer temperatures can result in higher ozone concentrations for a variety of reasons. These 

include increased evaporative emissions, increased biogenic emissions, and more rapid reactivity 

in the production of ozone. For these reasons warmer than normal temperatures can result in 

higher than normal ozone concentrations. Prolonged warmer than normal temperatures during 

the ozone season can also result in a higher than normal number of exceedances of the ozone 

Eight-Hour Ozone Attainment Plan
Attachment G Meteorological Representativeness of Recent Years 

G-11 

standard. These conditions can also lead to higher than normal peak 8-hour ozone 

concentrations. 

The summer of 2006 was much warmer than normal, resulting in the higher number of 8-hour 

ozone exceedances and higher concentrations measured at the Alpine monitoring station. 

Figure G-11 below shows the average monthly temperatures at the Alpine monitoring station for 

the year 2006 versus the 11-year averages for the years 1993 (first available year of 

meteorological data for the Alpine monitoring station) through 2003. This graph shows that 

average monthly temperatures in 2006 were much higher than normal during June and July, the 

peak ozone months of the typical ozone season. 

Figure G-11 

ALP 11-Year Average Temperature (1993 through 2003)

 vs. 2006

45.0

50.0

55.0

60.0

65.0

70.0

75.0

80.0

85.0

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

Month

Average Temperature (Degrees F)

11-Year Avg. Temperature

(1993 through 2003)

2006

Eight-Hour Ozone Attainment Plan
Attachment G Meteorological Representativeness of Recent Years 

G-12 

Figure G-12 below shows the monthly average temperature departure from the 11-year mean at 

Alpine. This chart shows that the average temperature at Alpine was more than 6°F warmer than 

normal during June and July of 2006. 

Figure G-12 

ALP Average Monthly Temperature Departure from 11-Year 

Average

-8.0

-6.0

-4.0

-2.0

0.0

2.0

4.0

6.0

8.0

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

Month

Temperature Departure (F)

Zero Departure from Average

2006

Eight-Hour Ozone Attainment Plan
Attachment G Meteorological Representativeness of Recent Years 

G-13 

Figure G-13 below shows the average temperature departure plotted along with the number of 

8-hour ozone exceedances at Alpine during 2006. 

Figure G-13 

ALP Average Temperature Departure vs. 8-Hour Ozone 

Exceedances

-8

-6

-4

-2

0

2

4

6

8

JAN FEB M AR APR M AY JUN JUL AUG SEP OCT NOV DEC

Month

Temperature Departure (F) / Monthly 

8-Hour Ozone Exceedances

ALP 2006 Temperature

Departure from Average

ALP Exceedances 2006

Eight-Hour Ozone Attainment Plan
Attachment G Meteorological Representativeness of Recent Years 

G-14 

Figure G-14 below shows that the higher than normal number of 8-hour ozone exceedances 

occurred during June and July of 2006, coinciding with the warmer than normal temperatures. 

Figure G-14 

ALP 8-Hour Federal Ozone Exceedances by Month

0.0

1.0

2.0

3.0

4.0

5.0

6.0

7.0

8.0

JANFEBMARAPRMAYJUNJULAUGSEPOCTNOVDEC

Month

Number of Exceedances

Average Exceedances: 1997

through 2003

Average Exceedances: 2003

to 2005

ALP Exceed 2006

Eight-Hour Ozone Attainment Plan
Attachment G Meteorological Representativeness of Recent Years 

G-15 

The monthly averaged temperature data for Lindbergh Field (SAN) are also shown in 

Figure G-15 below for consistency. This graph shows that monthly averaged temperatures at 

SAN were much warmer than the 30-year average for June and July (3.5° F and 5.6° F, 

respectively), and warmer during August as well (1.1° F). 

Figure G-15 

SAN 30-Year Average Monthly Temperature vs. Indicated Year

50.0

55.0

60.0

65.0

70.0

75.0

80.0

JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC

Month

Average Temperature (Degrees F)

30-Yr Avg

2006

Eight-Hour Ozone Attainment Plan
Attachment G Meteorological Representativeness of Recent Years 

G-16 

Figure G-16 below shows the cooling degree day data for 2006 compared to the 1997 through 

2003 average. This graph shows that the cooling degree values were much higher than normal 

for June and July, and higher than normal for August. In July 2006 a large portion of California 

was undergoing a prolonged heat wave, resulting in record electrical energy usage. 

The higher than normal number of 8-hour ozone exceedances and the higher concentrations in 

2006 were the result of anomalous meteorological conditions. Based on historical records, the 

likelihood that these anomalous conditions will repeat within the next few years is extremely 

remote and will not require new or expanded control measures in San Diego County to meet the 

8-hour ozone standard. 

Figure G-16 

Cooling Degree Days - San Diego, California

0

50

100

150

200

250

300

350

400

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

Month

Cooling Degree Days

Average(1997 through 2003)

2006

Eight-Hour Ozone Attainment Plan
ATTACHMENT H 

Meteorological and Photochemical Modeling 

for the San Diego County 2007 

Eight-Hour Ozone State Implementation Plan 

Eight-Hour Ozone Attainment Plan
Meteorological and Photochemical Modeling for the

San Diego County 2007

8 Hour Ozone State Implementation Plan

Prepared for

San Diego Air Pollution Control District

10124 Old Grove Road

San Diego, CA 92123

Prepared by

Kit K. Wagner, Ph.D.

Atmospheric Information Systems

P. O. Box 721165

Norman, OK 73070

April 4, 2007

Eight-Hour Ozone Attainment Plan
i

TABLE OF CONTENTS

1.0 INTRODUCTION .........................................................1

1.1 Conceptual Model of Ozone in San Diego County .............................1

1.2 Modeling Protocols ......................................................3

2.0 CHARACTERIZATION AND SELECTION OF MODELING EPISODES ............3

3.0 MODELING METHODS ....................................................4

3.1 Emissions .............................................................4

3.2 Meteorology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

3.2.1 Meteorological Model Selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

3.2.2 Domain, Terrain, and Land Use . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

3.2.3 Initial Conditions - August 3-8, 1997 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

3.2.4 MM5 Parameters and Four Dimensional Data Assimilation - August 3-8, 1997

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

3.2.5 Initial Conditions - September 24-30, 1997 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19

3.2.6 MM5 Parameters and Four Dimensional Data Assimilation - September 24-30,

1997 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19

3.2.7 Post Processing MM5 Outputs To CAMx Inputs . . . . . . . . . . . . . . . . . . . . . . . . . 23

3.3 Air Quality . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24

3.3.1 Photochemical Model Selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24

3.3.2 Modeling Domain . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24

3.3.3 Initial and Boundary Condition Inputs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26

3.3.4 Ancillary Inputs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28

3.3.5 CAMx Model Options . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28

4.0 EVALUATION OF MODEL PERFORMANCE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28

4.1 Emissions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28

4.2 Evaluation of Meteorological Model Output . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28

4.2.1 August 4-7, 1997, Episode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30

4.2.2 September 27-28, 1997, Episode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38

4.3 Evaluation of Air Quality Model Outputs for the Base Year August 4-7, 1997, Episode

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43

4.3.1 Evaluation of One-Hour Ozone Predictions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46

4.3.2 Evaluation of Eight-Hour Ozone Predictions . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52

4.4 Evaluation of Air Quality Model Outputs for the Base Year September 27-28, 1997,

Episode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57

4.4.1 Evaluation of One-Hour Ozone Predictions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57

4.4.2 Evaluation of Eight-Hour Ozone Predictions . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63

4.5 Source Apportionment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 68

Eight-Hour Ozone Attainment Plan
ii

5.0 MODELED OZONE ATTAINMENT TEST . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 72

5.1 Procedures for Design Values and Relative Reduction Factors . . . . . . . . . . . . . . . . . . 72

5.2 Eight-Hour Ozone Standard Attainment Demonstration Test . . . . . . . . . . . . . . . . . . . . 76

6.0 REFERENCES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 78

TABLES

Table 1. Factors to adjust 2010 CAMx emissions to 2008 CAMx emissions. ...............6

Table 2. Adjustments to 2008 area source emissions for military operations. ...............6

Table 3. San Diego County 1997 NOx emissions in tons per day for the August 4-7, 1997, ozone

episode. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

Table 4. San Diego County 1997 ROG emissions in tons per day for the August 4-7, 1997, ozone

episode. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

Table 5. San Diego County 2002 NOx emissions in tons per day for the August 4-7, 1997, ozone

episode. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

Table 6. San Diego County 2002 ROG emissions in tons per day for the August 4-7, 1997, ozone

episode. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

Table 7. San Diego County 2008 NOx emissions in tons per day for the August 4-7, 1997, ozone

episode. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

Table 8. San Diego County 2008 ROG emissions in tons per day for the August 4-7, 1997, ozone

episode. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

Table 9. San Diego County 1997 NOx emissions in tons per day for the September 27-28, 1997,

ozone episode. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

Table 10. San Diego County 1997 ROG emissions in tons per day for the September 27-28,

1997, ozone episode. ........................................................8

Table 11. San Diego County 2002 NOx emissions in tons per day for the September 27-28, 1997,

ozone episode. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

Table 12. San Diego County 2002 ROG emissions in tons per day for the September 27-28,

1997, ozone episode. ........................................................9

Table 13. San Diego County 2008 NOx emissions in tons per day for the September 27-28, 1997,

ozone episode. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

Table 14. San Diego County 2008 ROG emissions in tons per day for the September 27-28,

1997, ozone episode. ........................................................9

Table 15. Vertical structure of MM5 grid. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

Table 16. Modified LANDUSE.TBL file with original values in parentheses. . . . . . . . . . . . . . 18

Table 17. Vertical structure of the CAMx grid. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26

Table 18. Clean initial and boundary conditions for SAPRC99 species. . . . . . . . . . . . . . . . . . . 27

Table 19. Surface wind speed bias for August 3-7, 1997, for MM5 simulations. . . . . . . . . . . . 31

Table 20. Surface wind speed error for August 3-7, 1997, for MM5 simulations. . . . . . . . . . . 32

Table 21. Surface temperature bias for August 3-7, 1997, for MM5 simulations. . . . . . . . . . . . 33

Table 22. Surface temperature error for August 3-7, 1997, for MM5 simulations. . . . . . . . . . . 34

Table 23. Mixing height bias for August 3-7, 1997, for MM5 simulations. . . . . . . . . . . . . . . . 35

Table 24. Mixing height error for August 3-7, 1997, for MM5 simulations. . . . . . . . . . . . . . . . 36

Eight-Hour Ozone Attainment Plan
iii

Table 25. Surface wind speed bias for September 24-29, 1997, MM5 simulations. . . . . . . . . . 39

Table 26. Surface wind speed error for September 24-29, 1997, MM5 simulations. . . . . . . . . . 40

Table 27. Surface temperature bias for September 24-29, 1997, MM5 simulations. . . . . . . . . . 41

Table 28. Surface temperature error for September 24-29, 1997, MM5 simulations. . . . . . . . . 42

Table 29. Mixing height bias for September 26-29, 1997, MM5 simulations. . . . . . . . . . . . . . 43

Table 30. Mixing height error for September 26-29, 1997, for MM5 simulations. . . . . . . . . . . 43

Table 31. Ozone monitoring sites in San Diego County. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44

Table 32. One-hour averaged ozone model performance for San Diego County for the August

4-7, 1997, ozone episode. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46

Table 33. Eight-hour averaged ozone model performance for San Diego County for the August

4-7. 1997, ozone episode. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52

Table 34. One-hour averaged ozone model performance for San Diego County for the

September 27-28, 1997, ozone episode. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 58

Table 35. One-hour averaged ozone model performance for San Diego County for the

September 27-28, 1997, ozone episode excluding elevated sites. . . . . . . . . . . . . . . . . . . . . . 58

Table 36. Eight-hour averaged ozone model performance for San Diego County for the

September 27-28, 1997, ozone episode. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63

Table 37. Eight-hour averaged ozone model performance for San Diego County for the

September 27-28, 1997, ozone episode excluding elevated sites. . . . . . . . . . . . . . . . . . . . . . 64

Table 38. Source apportionment source regions. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 68

Table 39. San Diego Receptors for source apportionment. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 68

Table 40. Ozone source apportionment for August 5, 1997. . . . . . . . . . . . . . . . . . . . . . . . . . . . 70

Table 41. Ozone source apportionment for September 27, 1997. . . . . . . . . . . . . . . . . . . . . . . . 71

Table 42. Ozone source apportionment for the Alpine monitoring site for the August and

September episodes. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 71

Table 43. San Diego County eight-hour averaged ozone 4th highest concentration (ppb). . . . . 74

Table 44. San Diego County three year average of the 4th highest eight-hour ozone (ppb). . . . 74

Table 45. San Diego County eight-hour ozone design values (ppb). . . . . . . . . . . . . . . . . . . . . . 75

Table 46. Daily maximum predicted eight-hour ozone near a monitoring site . . . . . . . . . . . . . 76

Table 47. Future year eight-hour ozone design values. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 77

FIGURES

Figure 1. CAMx emissions adjustment regions. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

Figure 2. MM5 nested grids: D01 45 km grid; D02 15 km grid; D03 5 km grid. . . . . . . . . . . . 12

Figure 3. Photochemical modeling domain. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25

Figure 4. Mixing height (meters) from MM5 output. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37

Figure 5. Mixing height (meters) from CALMET output. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37

Figure 6. Ozone monitoring sites in San Diego County, SCOS97. . . . . . . . . . . . . . . . . . . . . . . 45

Figure 7a. Time series of one-hour averaged ozone and NOx in San Diego County, August 3-7,

1997. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48

Figure 7b. Time series of one-hour averaged ozone and NOx in San Diego County, August 3-7,

1997. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49

Figure 8a. Plot of maximum predicted one-hour averaged ozone for August 4, 1997. . . . . . . . 50

Eight-Hour Ozone Attainment Plan
iv

Figure 8b. Plot of maximum predicted one-hour averaged ozone for August 5, 1997. . . . . . . . 50

Figure 8c. Plot of maximum predicted one-hour averaged ozone for August 6, 1997. . . . . . . . 51

Figure 8d. Plot of maximum predicted one-hour averaged ozone for August 7, 1997. . . . . . . . 51

Figure 9a. Time series of eight-hour averaged ozone in San Diego County, August 3-7, 1997.

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54

Figure 9b. Time series of eight-hour averaged ozone in San Diego County, August 3-7, 1997.

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55

Figure 10a. Plot of maximum predicted eight-hour averaged ozone for August 4, 1997. . . . . . 55

Figure 10b. Plot of maximum predicted eight-hour averaged ozone for August 5, 1997. . . . . . 56

Figure 10c. Plot of maximum predicted eight-hour averaged ozone for August 6, 1997. . . . . . 56

Figure 10d. Plot of maximum predicted eight-hour averaged ozone for August 7, 1997. . . . . . 57

Figure 11a. Time series of one-hour averaged ozone and NOx in San Diego County, September

26-29, 1997. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 60

Figure 11b. Time series of one-hour averaged ozone and NOx in San Diego County, September

26-29, 1997. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61

Figure 12a. Plot of maximum predicted one-hour averaged ozone for September 26, 1997. . . 62

Figure 12b. Plot of maximum predicted one-hour averaged ozone for September 27, 1997. . . 62

Figure 12c. Plot of maximum predicted one-hour averaged ozone for September 28, 1997. . . 63

Figure 13a. Time series of eight-hour averaged ozone in San Diego County, September 26-29,

1997. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65

Figure 13b. Time series of eight-hour averaged ozone in San Diego County, September 26-29,

1997. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 66

Figure 14a. Plot of maximum predicted eight-hour averaged ozone for September 26, 1997.

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 66

Figure 14b. Plot of maximum predicted eight-hour averaged ozone for September 27, 1997.

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 67

Figure 14c. Plot of maximum predicted eight-hour averaged ozone for September 28, 1997.

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 67

Eight-Hour Ozone Attainment Plan
1

1.0 INTRODUCTION

A modeled attainment demonstration is required for the San Diego County portion of the

2007 State Implementation Plan for eight-hour averaged ozone. This document describes the

procedures used to apply meteorological and air quality models for that attainment

demonstration.

Meteorological and air quality models are used to simulate the meteorological and air

quality conditions during two ozone episodes that occurred during the 1997 Southern California

Ozone Study (SCOS97) (Croes and Fujita 2003). These episodes occurred August 4-7, 1997,

and September 27-28, 1997. SCOS97 provides an extensive meteorological and air quality

database that supports the development of a modeling application for the attainment

demonstration.

1.1 Conceptual Model of Ozone in San Diego County

Ozone in San Diego County originates from both distant and local sources. The staff of

the California Air Resource Board (ARB 1989) have identified the South Coast Air Basin as a

source region for ozone and ozone precursors transported into San Diego County. In a later

report the staff of the California Air Resource Board (ARB 1993) identified Mexico as a

contributor to ozone and ozone precursor transported into San Diego County. These California

Air Resource Board (ARB) reports summarize the studies of air pollution transport in California.

Because the predominant wind flow in Southern California is westerly (Hayes et al.

1984) transport from the South Coast Air Basin (SCAB) into San Diego County is infrequent. 

However, when the westerly flow weakens or is replace by easterly flow the possibility of

transport from the SCAB into San Diego County can develop. Hayes et al. (1984) indicate that

this happens 23 percent of the time in winter, 17 percent of the time in spring, 14 percent of the

time in summer, and 21 percent of the time in the fall. For transport to contribute to a significant

air quality impact several other meteorological factors must be present. The pollutants from the

SCAB must remain concentrated in a shallow marine layer below an elevated temperature

inversion or within a stable inversion layer aloft. Clear sky and low wind speed also contribute

to significant transport impacts. Emissions from the SCAB move to near the coast or are

transported westward offshore. Subsequent northwesterly winds transport these air pollutants

either along a path over the water into San Diego County or along a path inland near the

coastline. 

Pollutant transport from the SCAB is sufficient to produce high concentrations of ozone

at coastal sites without any contribution from San Diego emissions. Transported pollutants can

continue to move inland through the County where local emissions are added to produce high

ozone concentrations inland.

There are five meteorological scenarios associated with transport that contribute to high

ozone concentrations in San Diego County. Each scenario has a unique signature which can be

discerned from the surface and upper air meteorological and air quality data. In the first regime,

Eight-Hour Ozone Attainment Plan
2

polluted air from the Los Angeles area is transported over the coastal waters into San Diego near

the surface (100 to 300 meters above sea level), in or below a surface based or very low

elevation marine inversion. High ozone concentrations of ozone are observed at San Diego

coastal air monitoring sites near sea level such as Oceanside or Del Mar. Inland sites may have

much lower ozone concentrations. Local emissions of NO react with the transported ozone to

form NO2 and reduce the concentration of the transported ozone. Sites near the coast such as

Overland observe a lower ozone concentration as the transported pollution arrives than would

have been observed in the absence of NOx scavenging.

In the second regime, polluted air from the Los Angeles area is transported aloft (300 to

500 meters above sea level) over the coastal waters into San Diego near the base or within a

slightly elevated marine inversion. As the air moves inland it either encounters the elevated

mesas (approximately 150 meter above sea level) in the coastal plain or is mixed downward

(fumigated) to the surface. Fumigation occurs because of convection caused by solar heating of

the ground surface inland. High ozone concentrations are observed at the inland stations such as

Escondido and Overland, while ozone concentrations at the coastal stations are less, being below

the ozone aloft. At the inland stations ozone concentrations are low until the transported ozone

arrives. Local NO emissions will scavenge the fumigated ozone and local ROG and NOx

emissions may make a contribution to additional ozone generation as the air moves further

inland.

The third regime also involves transport aloft, but at a higher elevation (500 to 1000

meters above sea level). The marine layer is deeper and the transport is at the base or in the

elevated marine inversion. As the polluted air moves inland into San Diego County the ozone

aloft is not fumigated to the surface until the air has reached the inland elevated foothills. High

ozone concentrations in this regime are observed at sites such as Alpine.

The fourth transport route is emissions from the Inland Empire (i.e., Riverside County)

transported near the surface down the Interstate 15 corridor under northerly wind conditions. 

This regime usually impacts the air quality at the inland Escondido and Overland monitoring

stations.

The fifth regime is for transport of ozone and ozone precursors from Mexico, namely the

city of Tijuana, which lies to the south of San Diego. This transport regime requires southerly

winds at some time during the day. Southerly winds are usually associated with coastal eddy

circulations. These conditions can transport urban pollutants, including ozone, from Tijuana

during the daytime hours (impacts Otay Mesa and El Cajon stations), or transport ozone

precursors offshore during nighttime drainage along the Tijuana River basin and then back

onshore into San Diego County (impacting Chula Vista, Downtown, Otay Mesa, or Overland

monitoring stations) the next day.

The meteorological conditions associated with ozone transport are part of the normal

atmospheric circulation patterns of Southern California and are therefore repeatable. All ozone

transport corridors have been identified through extensive data analysis of past events (ARB

1996).

Eight-Hour Ozone Attainment Plan
3

Emissions in San Diego County are sufficient to generate ozone concentrations

exceeding the state and federal standards. Ozone precursors of NOx and ROG are emitted in the

high population density areas near the coast in the morning. Ozone is created by chemical

reactions as the sea breeze carries the precursors inland. Maximum ozone concentrations are

reached in the early afternoon to the east of the coastal plain. When transport is completely

absent, local emissions are the sole source of ozone in the County. This is usually evidenced by

a lack of a northerly or southerly component to the wind near the surface and aloft.

1.2 Modeling Protocols

Modeling protocols were prepared to guide the modeled attainment demonstration for

San Diego County. General modeling procedures appear in a modeling protocol for Southern

California (ARB 2000). Specific modeling procedures for San Diego County appear in a

supplement (SDAPCD 2002). These protocols are attached to this document.

2.0 CHARACTERIZATION AND SELECTION OF MODELING EPISODES

August 4-7, 1997, is an ozone episode where both local contributions and transport

contributed to exceedances of the ozone standards in San Diego County. Peak one-hour ozone

during this episode was 0.12 ppm on August 3 at Alpine and on August 5 at Otay Mesa. 

Exceedances of the California one-hour standard (0.09 ppm) were wide spread on August 5. 

Alpine alone exceeded the California one-hour standard on August 6. The peak eight-hour

averaged ozone in San Diego County during this episode was 0.099 ppm which occurred at a

supplemental monitor (Black Mountain). The highest eight-hour averaged ozone at an official

monitor was 0.087 at Alpine on August 5. The peak 1-hour ozone concentration of 0.19 ppm

and the peak 8 hour concentration of 0.125 ppm measured in the South Coast air basin during

this period were the highest not associated with an exceptional event during SCOS97.

The meteorological conditions during this August 1997, ozone episode have been

characterized in detail by Rosenthal et al. (2003) and by Boucouvala and Bornstein (2003). The

meteorological episode began on Sunday August 3 under a ridge of high pressure aloft with 500

mb heights in excess of 5900m each day. Weak onshore flow gave way to stagnant winds

through the middle of the episode, ultimately resulting in a well developed coastal eddy

beginning late on August 6th and continuing into August 7th. The excessive regional surface

temperatures and stagnant flow also contributed to a massive wildfire in the mountainous

portions of eastern Ventura and southeastern Santa Barbara counties during the later part of the

episode.

September 27-28, 1997, is weekend episode. Peak one-hour averaged ozone in San

Diego County occurred on Sunday, September 28, with a concentration of 0.11 ppm at Alpine. 

Additional exceedances of the California one-hour standard occurred at other monitors in the

County. Both local sources and transport contributed to the exceedances. Exceedances of the

ozone standard on weekends are important in San Diego County. In 1997 forty-two percent of

the days with exceedances of the California one-hour ozone standard were on Saturday or

Sunday. In 2001 this had increased to fifty-two percent. In San Diego County during this

Eight-Hour Ozone Attainment Plan
4

episode 0.096 ppm was the peak eight-hour averaged ozone which occurred at a supplemental

monitor (Black Mountain). Eight-hour averaged ozone did not exceed 0.084 ppm at the official

monitors during this episode. This episode includes the second highest ozone concentrations

measured in the South Coast air basin during a SCOS97 intensive operations period. The peak

1-hour (0.17 ppm) and 8 hour (0.107 ppm) ozone concentrations in the South Coast air basin

were both observed at Upland. 

3.0 MODELING METHODS

The modeled attainment demonstration is carried out using the Comprehensive Air

Quality Model with Extensions (CAMx) to model ozone in San Diego County. Version 4.20

(ENVIRON 2005) of CAMx with the SAPRC99 chemical mechanism is used. CAMx requires

emission, meteorological, and air quality data inputs. The procedures used to prepare those

inputs are described below.

3.1 Emissions

The emission inputs were prepared by the California Air Resources Board (ARB) staff

and delivered to the San Diego Air Pollution Control District (SDAPCD) in CAMx-ready point

source and area source emission input files. The ROG emissions were speciated for the

SAPRC99 chemical mechanism. The CAMx area source file was delivered in five separate

component files: 

• area source emissions

• motor vehicle emissions

• biogenic emissions

• smaller point source emissions not placed in the point source file

• Mexico emissions

These components were aggregated into a single CAMx area source input file for the simulation.

The CAMx point source file was delivered in three component files:

• large point source emissions

• large Mexico point source emissions

• wildfire emissions

These components were aggregated into a single CAMx point source file for the simulation.

The ARB provided 1997, 2002, and 2010 emissions for the August 3-7, 1997, period. 

August 3 is a Sunday. August 4-7 is Monday to Thursday. These emissions were day specific

for motor vehicle, biogenic, and wildfire emissions. The area source, large point source, and

smaller point source emissions were for a mid-summer weekday and a mid-summer weekend

day. The Mexico area source emissions were for a single summer day. The Mexico large point

source emissions were not used because of uncertainty in emission rates and locations of

Eight-Hour Ozone Attainment Plan
5

sources. The 1997 biogenic and Mexico emissions were used unchanged for 2002 and 2010. 

Wildfire emissions were not included in the 2002 and 2010 emissions.

 For September 24, 25, 26, and 29 (Wednesday, Thursday, Friday, Monday) the area

source, small point source, motor vehicle, and large point source emission inputs are the August

4, 1997, (Monday) emissions. For September 27 and 28 (Saturday and Sunday) the area source,

small point source, motor vehicle, and large point source emission inputs are the August 3, 1997,

(Sunday) emissions. The ARB provided 1997 biogenic emissions for September 27, 1997,

which were used for all September days. Mexico emissions are the same as for the August

episode. Wildfires were not included in the large point source emissions for the September 24-

29. 1997, period or the 2002 and 2010 future year emissions.

The ARB was unable to provide a 2008 emission inventory. The year 2008 is the year

required for the modeled attainment demonstration. A 2008 CAMx emission inventory for the

August 4-7, 1997, ozone episode was created by projecting the 2010 CAMx area sources, small

point sources, large point sources, and motor vehicles emissions back to 2008. The adjustment

factors for projecting the modeling emissions, which were developed by the San Diego Air

Pollution Control District (SDAPCD) staff, are based on the changes in the planning emission

inventories for 1997, 2002, 2008, and 2010. The modeling domain was divided into four regions

and separate adjustment factors calculated for each region. The four regions are: (1) offshore

north of the Orange County - San Diego County line; (2) offshore south of that line; (3) onshore

north of the Orange County/Riverside County - San Diego County line; (4) onshore south of that

line. These factors were applied uniformly to all source categories within the general categories. 

Figure 1 shows the areas in the modeling domain. The adjustment factors are listed in Table 1.

Figure 1. CAMx emissions adjustment regions.

There are several changes in military operations emission sources in 2008 in San Diego

County that are not in the ARB 2010 emission inventory. These emission adjustments were

made to the 2008 CAMx area source emission file after the 2008 emissions were created from

the 2010 emissions using the projection factors in Table 1 and aggregated into the CAMx input

file. These emission adjustments are listed in Table 2.

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Table 1. Factors to adjust 2010 CAMx emissions to 2008 CAMx emissions.

Emission

Component

South Coast

Offshore

South Coast

Onshore

San Diego Offshore San Diego Onshore

ROG NOx ROG NOx ROG NOx ROG NOx

Area source 1.005726 0.952796 1.023532 1.116261 1.020826 0.960846 1.016061 1.064352

Small point source 1.023532 1.116261 1.023532 1.116261 1.016061 1.064352 1.016061 1.064352

Motor vehicle 1.143991 1.095840 1.143991 1.095840 1.136895 1.112645 1.136895 1.112645

Biogenic 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0

Mexico 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0

Large point source 1.023532 1.116261 1.023532 1.116261 1.016061 1.064352 1.016061 1.064352

Table 2. Adjustments to 2008 area source emissions for military operations.

Source Location: grid cell 

(west-east, south-north)

NOx

(tons/day)

VOC

(tons/day)

Offshore San Diego Harbor (73, 13) +0.6 0.0

Miramar Air Station (75, 19) +1.0 -1.8

Camp Pendleton (70, 28) +0.7 -0.1

For 2008 September 24, 25, 26, and 29 (Wednesday, Thursday, Friday, Monday) the area

source, small point source, motor vehicle, and large point source emission inputs are the 2008

August 4 (Monday) emissions. For 2008 September 27 and 28 (Saturday and Sunday) the area

source, small point source, motor vehicle, and large point source emission inputs are the 2008

August 3 (Sunday) emissions. The ARB provided 1997 biogenic emissions for September 27,

1997, which were used for all September days in 2008. Mexico emissions are the same as for

the August episode for 2008. 

Emission totals for San Diego County for ROG and NOx for the August 4-7, 1997, ozone

episode for the years 1997, 2002, and 2008 are listed in Tables 3 to 8. Emission totals for San

Diego County for ROG and NOx for the September 27-28, 1997, ozone episode for the years

1997, 2002, and 2008 are listed in Tables 9 to 14. The Mexico emissions listed in the tables

occur in grid cells divided by the San Diego County-Mexico border.

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Table 3. San Diego County 1997 NOx emissions in tons per day for the August 4-7, 1997, ozone episode.

Day area small point motor vehicle biogenic Mexico Total area large point w

Sunday 3-Aug 73.2 0.6 105.5 0 5.5 184.9 0.1 

Monday 4-Aug 89.0 8.7 139.2 0 5.5 242.4 5.8 

Tuesday 5-Aug 89.0 8.7 144.6 0 5.5 247.7 5.8 

Wednesday 6-Aug 89.0 8.7 138.0 0 5.5 241.2 5.8 

Thursday 7-Aug 89.0 8.7 134.4 0 5.5 237.6 5.8 

Table 4. San Diego County 1997 ROG emissions in tons per day for the August 4-7, 1997, ozone episode.

Day area small point motor vehicle biogenic Mexico Total area large point w

Sunday 3-Aug 147.8 1.4 108.2 130.9 16.0 404.3 0 

Monday 4-Aug 141.1 15.9 131.7 137.7 16.0 442.4 0.4 

Tuesday 5-Aug 141.1 15.9 138.8 162.4 16.0 474.2 0.4 

Wednesday 6-Aug 141.1 15.9 133.4 139.5 16.0 445.9 0.4 

Thursday 7-Aug 141.1 15.9 127.3 86.1 16.0 376.4 0.4 

Table 5. San Diego County 2002 NOx emissions in tons per day for the August 4-7, 1997, ozone episode.

Day area small point motor vehicle biogenic Mexico Total area Total point

Sunday 3-Aug 78.5 0 86.7 0 5.5 168.0 0

Monday 4-Aug 83.2 5.4 118.3 0 5.5 212.5 1.8

Tuesday 5-Aug 83.2 5.4 122.3 0 5.5 216.4 1.8

Wednesday 6-Aug 83.2 5.4 117.4 0 5.5 211.6 1.8

Thursday 7-Aug 83.2 5.4 114.7 0 5.5 208.9 1.8

Table 6. San Diego County 2002 ROG emissions in tons per day for the August 4-7, 1997, ozone episode.

Day area small point motor vehicle biogenic Mexico Total area Total point

Sunday 3-Aug 144.8 0.1 73.0 130.9 16.0 364.8 0

Monday 4-Aug 130.7 17.1 88.0 137.7 16.0 390.2 0.4

Tuesday 5-Aug 130.7 17.1 93.4 162.4 16.0 419.6 0.4

Wednesday 6-Aug 130.7 17.1 89.9 139.5 16.0 393.2 0.4

Thursday 7-Aug 130.7 17.1 86.2 86.1 16.0 336.1 0.4

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Table 7. San Diego County 2008 NOx emissions in tons per day for the August 4-7, 1997, ozone episode.

Day area small point motor vehicle biogenic Mexico Total area Total area* To

Sunday 3-Aug 79.2 0 64.0 0 5.5 148.7 151.0 

Monday 4-Aug 82.1 6.5 91.8 0 5.5 186.0 188.3 

Tuesday 5-Aug 82.1 6.5 94.2 0 5.5 188.4 190.7 

Wednesday 6-Aug 82.1 6.5 91.1 0 5.5 185.3 187.6 

Thursday 7-Aug 82.1 6.5 89.6 0 5.5 183.8 186.1 

*Total includes adjustments for military operations emissions.

Table 8. San Diego County 2008 ROG emissions in tons per day for the August 4-7, 1997, ozone episode.

Day area small point motor vehicle biogenic Mexico Total area Total area* To

Sunday 3-Aug 129.2 0 48.1 130.9 16.0 324.2 322.4 

Monday 4-Aug 127.0 20.7 58.4 137.7 16.0 359.8 357.9 

Tuesday 5-Aug 127.0 20.7 62.1 162.4 16.0 388.2 386.3 

Wednesday 6-Aug 127.0 20.7 59.3 139.5 16.0 362.5 360.7 

Thursday 7-Aug 127.0 20.7 56.1 86.1 16.0 305.9 304.0 

*Total includes adjustments for military operations emissions.

Table 9. San Diego County 1997 NOx emissions in tons per day for the September 27-28, 1997, ozone episode.

Day area small point motor vehicle biogenic Mexico Total area Total point

Thursday 25-Sep 89.0 8.7 139.2 0 5.5 242.4 5.8

Friday 26-Sep 89.0 8.7 139.2 0 5.5 242.4 5.8

Saturday 27-Sep 73.2 0.6 105.5 0 5.5 184.8 0.1

Sunday 28-Sep 73.2 0.6 105.5 0 5.5 184.8 0.1

Monday 29-Sep 89.0 8.7 139.2 0 5.5 242.4 5.8

Table 10. San Diego County 1997 ROG emissions in tons per day for the September 27-28, 1997, ozone episode

Day area small point motor vehicle biogenic Mexico Total area Total point

Thursday 25-Sep 141.1 15.9 131.7 61.8 16.0 366.6 0.4

Friday 26-Sep 141.1 15.9 131.7 61.8 16.0 366.6 0.4

Saturday 27-Sep 147.8 1.4 108.2 61.8 16.0 335.2 0.0

Sunday 28-Sep 147.8 1.4 108.2 61.8 16.0 335.2 0.0

Monday 29-Sep 141.1 15.9 131.7 61.8 16.0 366.6 0.4

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Table 11. San Diego County 2002 NOx emissions in tons per day for the September 27-28, 1997, ozone episode

Day area small point motor vehicle biogenic Mexico Total area Total point

Thursday 25-Sep 83.2 5.4 118.3 0 5.5 212.5 1.8

Friday 26-Sep 83.2 5.4 118.3 0 5.5 212.5 1.8

Saturday 27-Sep 75.8 0 86.7 0 5.5 168.0 0

Sunday 28-Sep 75.8 0 86.7 0 5.5 168.0 0

Monday 29-Sep 83.2 5.4 118.3 0 5.5 212.5 1.8

Table 12. San Diego County 2002 ROG emissions in tons per day for the September 27-28, 1997, ozone episode

Day area small point motor vehicle biogenic Mexico Total area Total point

Thursday 25-Sep 130.7 17.1 88.8 61.8 16.0 314.4 0.4

Friday 26-Sep 130.7 17.1 88.8 61.8 16.0 314.4 0.4

Saturday 27-Sep 144.8 0.1 73.0 61.8 16.0 295.7 0.0

Sunday 28-Sep 144.8 0.1 73.0 61.8 16.0 295.7 0.0

Monday 29-Sep 130.7 17.1 88.8 61.8 16.0 314.4 0.4

Table 13. San Diego County 2008 NOx emissions in tons per day for the September 27-28, 1997, ozone episode

Day area small point motor vehicle biogenic Mexico Total Area Total area* To

Thursday 25-Sep 82.1 6.5 91.8 0 5.5 186.0 188.3 

Friday 26-Sep 82.1 6.5 91.8 0 5.5 186.0 188.3 

Saturday 27-Sep 79.2 0 64.0 0 5.5 148.7 151.0 

Sunday 28-Sep 79.2 0 64.0 0 5.5 148.7 151.0 

Monday 29-Sep 82.1 6.5 91.8 0 5.5 186.0 188.3 

*Total includes adjustments for military operations emissions.

Table 14. San Diego County 2008 ROG emissions in tons per day for the September 27-28, 1997, ozone episode

Day area small point motor vehicle biogenic Mexico Total area Total area* To

Thursday 25-Sep 127.0 20.7 58.4 61.8 16.0 283.9 282.1 

Friday 26-Sep 127.0 20.7 58.4 61.8 16.0 283.9 282.1 

Saturday 27-Sep 129.2 0 48.1 61.8 16.0 255.1 253.4 

Sunday 28-Sep 129.2 0 48.1 61.8 16.0 255.1 253.4 

Monday 29-Sep 127.0 20.7 58.4 61.8 16.0 283.9 282.1 

*Total includes adjustments for military operations emissions.

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3.2 Meteorology

3.2.1 Meteorological Model Selection

Sonoma Technology Inc. (STI) (Wheeler 2003) examined prior meteorological modeling

of the SCOS97 episodes. STI recommended that the SDAPCD use MM5 for its meteorological

modeling. The STI report also made specific recommendations for implementing MM5 for San

Diego County. MM5 is a prognostic non-hydrostatic mesoscale model. The application of

MM5 in California has been described by Seaman et al. (1995).

A second meteorological model, CALMET (Scire et al. 2000), is also used in the

preparation of meteorological inputs to the air quality model. CALMET is a diagnostic

meteorological model with extensive micro-meteorological parameterizations of the atmospheric

boundary layer. CALMET is used to calculate the planetary boundary layer heights for

estimating the atmospheric vertical mixing coefficients for CAMx.

3.2.2 Domain, Terrain, and Land Use

The meteorological modeling uses the same domains as indicated in the modeling

protocols (ARB 2000, SDAPCD 2002) except the 5 km resolution interior domain is expanded to

provide boundary cells on each side of the photochemical modeling domain. MM5 is executed

on three nested domains. The outer coarse domain has a resolution of 45 km grid cells. This

coarse domain is 63 cells east-west by 61 cells north-south. The next interior domain has a

resolution of 15 km grid cells with 85 cells east-west and 91 cells north-south. The innermost

domain has a resolution of 5 km grid cells with 91 grid cells east-west and 127 grid cells northsouth. The domains are defined as:

• A Lambert Conformal map projection

• True latitudes of 30.0 degrees North and 60.0 degrees North

• A central longitude of 118.00 degree West

• The center of the projection is at 34.54 degrees North and 118.0 degrees West

• The center of the coarse 45 km resolution domain (63 x 61) is at 34.54 degrees

North and 118.0 degrees West.

• The southwest corner grid cell of the 15 km resolution domain (91 x 85) is at cell

17 east-west, 17 north-south in the 45 km resolution domain

• The southwest corner grid cell of the 5 km resolution domain (127 x 91) is at cell

23 east-west, 25 north-south in the 15 km resolution domain

The three nested grids are shown in Figure 2. The meteorological variables from the 5km

MM5 grid are mapped into the CAMx grid. The CAMx grid is offset to the northeast of the

MM5 5 km grid. This offset is to allow for the 5 boundary cells on each side of the MM5 5 km

grid to surround the CAMx grid.

The terrain elevations are defined in the MM5 TERRAIN file. Terrain elevations are

extracted from a database from the National Center for Atmospheric Research (NCAR). The

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terrain elevations for the coarse grid are determined from 5 arc-minute resolution terrain data. 

The terrain elevations for the 15 km grid are determined from 2 arc-minute resolution terrain

data. The terrain elevations for the 5 km grid are determined from 30 arc second resolution

terrain data. The actual terrain elevations from the databases are used to create the TERRAIN

file.

Land use for each grid cell is defined in the TERRAIN file. As with the terrain

elevations NCAR 5 arc-minute, 2 arc-minute, and 30 arc second data are used for the three

domains. The 25 category land use data is used. The land use in the grid cells where the Salton

Sea is located is changed from water to wetland as recommended by Wheeler (2003). The high

temperatures of the Salton Sea and surrounding land are inconsistent with the parameterization

of the area as a water body.

The TERRAIN file for the 5 km domain and for those grid cells covered by the Salton

sea was edited to change the land use category from water (category 16) to wetland (category

17). The LANDUSE.TBL file for MM5 was edited for category 17 to specify albedo, emissivity

fraction, roughness length, snow effect factor, and bulk heat capacity to be the same as a water

body. Soil moisture availability fraction was changed to 0.50.

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Figure 2. MM5 nested grids: D01 45 km grid; D02 15 km grid; D03 5 km grid.

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3.2.3 Initial Conditions - August 3-8, 1997

The MM5 simulation is initialized at 1200 UTC on August 3, 1997, and run 120 hours

until 1200 UTC on August 8, 1997. The first step in preparing the initial conditions and

boundary conditions for MM5 is to create the REGRID file. This file has horizontal two

dimensional slabs of meteorological data such as winds, temperature, and moisture specified on

several pressure surfaces (such as 500hPa) for each of a domain’s grid cells. These

meteorological fields are interpolated from global or regional analyses on a different grid to the

specific grid structure of the MM5 domains. Subsequent steps will interpolate the data vertically

to the MM5 vertical grid structure.

Input data for this step come from global or large scale meteorological analyses. The

National Center for Environmental Prediction (NCEP) Eta Data Assimilation System (EDAS)

database is used as input. The NCEP EDAS are three-dimensional fields of meteorological

variables at 40 km spatial resolution analyzed every 3 hours. 

For sea surface temperature (SST) inputs we obtained SST data from the California

Institute of Technology Jet Propulsion Laboratory (JPL) web site. JPL archives the NOAA/

NASA AVHRR Oceans Pathfinder sea surface temperature data which are derived from the 5-

channel Advanced Very High Resolution Radiometers (AVHRR) on board the NOAA -7, -9, -11

and -14 polar orbiting satellites. We obtained the 9 km resolution SST data for the August 1997

monthly averaged sea surface temperatures. We used the monthly averaged data set because the

daily data have many spatial gaps due to cloud cover. There are two monthly data sets, one for

daytime SSTs and one for nighttime SSTs. We applied the daytime SSTs at 12 and 18 UTC and

the nighttime SSTs at 00 and 06 UTC.

The next steps in preparing the initial and boundary conditions and four-dimensional data

assimilation (FDDA) inputs are the RAWINS/LITTLE_R and INTERP preprocessors. The

RAWINS and LITTLE_R are two different versions of preprocessor programs that use the

REGRID output analyses as a first guess and then interpolates observed upper air and surface

data to create analyses on pressure surfaces. The purpose of this step is to introduce higher

spatial resolution observational data into the coarser spatial resolution global or regional

analyses. Because the EDAS data already have surface and upper air observations on a smaller

scale contributing to the analysis the RAWINS/LITTLE_R processors were not run. The output

from REGRID was input directly into the INTERP processor.

 The INTERP preprocessor interpolates the output from REGRID vertically to the MM5

vertical coordinates. We used a 30-layer vertical grid structure for MM5. The vertical grid

structure is defined in MM5 in a sigma coordinate system based on pressure, (P), normalized by

the difference between the surface pressure, (Ps), and the pressure at the top of the domain, (Pt

).

σ = (P - Pt

)/(Ps - Pt)

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The 31 sigma levels at the top and bottom of the 30 vertical layers are specified in Table

15. The height and pressure are calculated for a reference atmosphere with surface pressure of

100000Pa, surface temperature 275K, lapse rate of 50 K/lnP, and 10000Pa pressure at the top.

Table 15. Vertical structure of MM5 grid.

Layer Top and Bottom Layer Center

sigma Pressure

Pa

Height

meters

1⁄2 sigmas Pressure

Pa

Height

meters

0 10000 14649

0.035 13150 13314 0.0175 11575 13950

0.07 16300 12189 0.0525 14725 12730

0.11 19900 11084 0.09 18100 11616

0.156 24040 9984 0.133 21970 10514

0.199 27910 9077 0.1775 25975 9518

0.241 31690 8281 0.22 29800 8669

0.284 35560 7538 0.2625 33625 7901

0.326 39340 6870 0.305 37450 7197

0.372 43480 6194 0.349 41410 6526

0.423 48070 5502 0.3975 45775 5841

0.464 51760 4982 0.4435 49915 5238

0.508 55720 4456 0.486 53740 4715

0.552 59680 3958 0.53 57700 4204

0.6 64000 3445 0.576 61840 3698

0.65 68500 2940 0.625 66250 3189

0.698 72820 2479 0.674 70660 2706

0.74 76600 2093 0.719 74710 2284

0.777 79930 1766 0.7585 78265 1928

0.814 83260 1450 0.7955 81595 1606

0.84 85600 1233 0.827 84430 1341

0.866 87940 1022 0.853 86770 1127

0.884 89560 878 0.875 88750 950

0.902 91180 737 0.893 90370 807

0.918 92620 613 0.91 91900 674

0.934 94060 490 0.926 93340 551

0.95 95500 369 0.942 94780 429

0.966 96940 249 0.958 96220 309

0.98 98200 146 0.973 97570 198

0.992 99280 58 0.986 98740 102

1 100000 0 0.996 99640 29

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3.2.4 MM5 Parameters and Four Dimensional Data Assimilation - August 3-8, 1997

Various parameters for MM5 are set to govern the execution of the simulation. The

ICUPA control parameter is set to1 for the 5 km domain to turn off cumulus parameterization. 

The parameter ICUPA was set to 6, Kain-Fritch parameterization, for the 45 km and 15 km

domains. To change the moisture availability for grassland, shrubland and irrigated cropland we

modified the LANDUSE.TBL file which is read during MM5 execution. We made additional

changes to the LANDUSE.TBL file for roughness length to implement recommendations from

Boucouvala et al. (2003). The values for the parameters in LANDUSE.TBL are shown in Table

16. The soil treatment was simplified by setting the control parameter ISOIL to 0 which

implements the Blackadar force/restore slab model. 

The MM5 simulation used four dimensional data assimilation (FDDA) with observed

meteorological analyses and observation to “nudge” the predictions toward the observed state. 

The observational data set includes SCOS97 surface and radar wind profiler meteorological

observations. The parameters used for FDDA are indicated below where the MM5 input stream

for FDDA parameters are reproduced for the August 3-8, 1997, MM5 simulation. The first

parameter value on a line is for the 45 km domain, the second for the 15 km domain, and the

third for the 5 km domain.

; **************** ANALYSIS NUDGING ******************

; IS THIS A GRID 4DDA RUN? 0 = NO; 1 = YES

I4D= 1,1,1, ;Three-dimensional analysis nudging

 0,1,0, ;Surface analysis nudging

 ; SPECIFY THE TIME IN MINUTES BETWEEN THE INPUT USED FOR GRID FDDA

 DIFTIM=360.,360.,360., ; Three-dimensional analysis nudging

 180.,180.,180., ; Surface analysis nudging

 IWIND=1,1,1, ;Three-dimensional analysis nudging

 0,1,0, ; Surface analysis nudging

; NUDGING COEFFICIENT FOR WINDS ANALYSES

 GV=2.5E-4,2.5E-4,1.0E-4, ; Three-dimensional analysis nudging

 2.5E-4,2.5E-4,1.0E-4, ; Surface analysis nudging

; GRID NUDGE THE TEMPERATURE FIELD? 0 = NO; 1 = YES

 ITEMP=1,1,0, ; Three-dimensional analysis nudging

 0,0,0, ; Surface analysis nudging

; NUDGING COEFFICIENT FOR TEMPERATURE ANALYSES

 GT=2.5E-4,2.5E-4,1.0E-4, ; 3D ANALYSIS NUDGING

 2.5E-4,2.5E-4,1.0E-4, ; SFC ANALYSIS NUDGING

 IMOIS=1,1,0, ; 3D ANALYSIS NUDGING

 0,0,0, ; SFC ANALYSIS NUDGING

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 ; NUDGING COEFFICIENT FOR THE MIXING RATIO ANALYSES

 GQ=1.E-5,1.E-5,1.0E-5, ; 3D ANALYSIS NUDGING

 1.E-5,1.E-5,1.0E-5, ; SFC ANALYSIS NUDGING

 ; GRID NUDGE THE ROTATIONAL WIND FIELD? 0 = NO; 1 = YES

 IROT=0,0,0, ; 3D ANALYSIS NUDGING

 ; NUDGING COEFFICIENT FOR THE ROTATIONAL COMPONENT OF THE WINDS

 GR=0.,0.,0., ; 3D ANALYSIS NUDGING

 ; IF GRID NUDGING (I4D(1,1)=1) AND YOU WISH TO EXCLUDE THE

 ; BOUNDARY LAYER FROM FDDA OF COARSE GRID THREE DIMENSIONAL

 ; DATA (USUALLY FROM INTERP),

 ; 0 = NO, INCLUDE BOUNDARY LAYER NUDGING

 ; 1 = YES, EXCLUDE BOUNDARY LAYER NUDGING

 INONBL =1,0,0, ; U WIND

 1,0,0, ; V WIND

 1,1,1, ; TEMPERATURE

 1,1,1, ; MIXING RATIO

 ; RADIUS OF INFLUENCE FOR SURFACE ANALYSIS (KM).

 RINBLW=250.,

 ; **************** OBSERVATION NUDGING ***************

 ; IS THIS INDIVIDUAL OBSERVATION NUDGING? 0 = NO; 1 = YES

 I4DI =0,1,1,

 ; OBS NUDGE THE WIND FIELD FROM STATION DATA? 0 = NO; 1 = YES

 ISWIND =0,1,1,

 ; NUDGING COEFFICIENT FOR WINDS FROM STATION DATA

 GIV =4.E-3,4.E-3,4.E-3,

 ; OBS NUDGE THE TEMPERATURE FIELD FROM STATION DATA? 0 = NO; 1 = YES

 ISTEMP=0,1,1,

 ; NUDGING COEFFICIENT FOR TEMPERATURES FROM STATION DATA

 GIT =4.E-4,4.E-4,4.E-4,

 ; OBS NUDGE THE MIXING RATIO FIELD FROM STATION DATA? 0 = NO; 1 = YES

 ISMOIS=0,1,1,

 ; NUDGING COEFFICIENT FOR THE MIXING RATIO FROM STATION DATA

 GIQ =4.E-4,4.E-4,4.E-4,

 RINXY=30.,

 RINSIG=0.001,

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 TWINDO=40.0,

 ; FREQUENCY (IN CGM TIMESTEPS) TO COMPUTE OBS NUDGING WEIGHTS

 IONF=2,

 IDYNIN=0, ;for dynamic initialization using a ramp-down function to gradually

 ; turn off the FDDA before the pure forecast, set idynin=1 [y=1, n=0]

 DTRAMP=60.,;the time period in minutes over which the

 ; nudging (obs nudging and analysis nudging) is ramped down

 ; from one to zero. 

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Table 16. Modified LANDUSE.TBL file with original values in parentheses.

Category

Number

Albedo

percent

Soil Moisture 

Availability

fraction

Emissivity at 9nm

fraction

Roughness

Length

cm

Thermal Inertial

100*cal cm-2K-1s-1/2

Snow Effect Factor

fraction

Bulk Heat

Capacity

J m-3K-1

1 18. .10 .88 150.(50.) 3. .52 18.9e5 Urban and B2 17. .30 .92 15. 4. .60 25.0e5 Dryland Crop3 18. .30(.50) .92 15. 4. .60 25.0e5 Irrigated Cro4 18. .25 .92 15. 4. .60 25.0e5 Mixed Drylan5 18. .25 .92 14. 4. .60 25.0e5 Cropland/Gra6 16. .35 .93 20. 4. .60 25.0e5 Cropland/Wo7 19. .05(.15) .92 10.(12.) 3. .60 20.8e5 Grassland8 22. .05(.10) .88 20.(10.) 3. .62 20.8e5 Shrubland9 20. .05(.15) .90 30.(11.) 3. .60 20.8e5 Mixed Shrub10 20. .15 .92 40.(15.) 3. 0. 25.0e5 Savanna11 16. .30 .93 100.(50.) 4. .56 25.0e5 Deciduous B12 14. .30 .94 50. 4. .50 25.0e5 Deciduous N13 12. .50 .95 50. 5. 0. 29.2e5 Evergreen B14 12. .30 .95 100.(50.) 4. .50 29.2e5 Evergreen N15 13. .30 .94 50. 4. .54 41.8e5 Mixed Forest16 8. 1.0 .98 1.(.01) 6. 0. 9.0e25 Water Bodies17 8.(14.) .50(.60) .98(.95) 1.(20.) 6. 0.(.55) 9.0e25(29.2e5) Herbaceous 18 14. .35 .95 40. 5. .58 41.8e5 Wooded Wet19 25. .02 .85 10. 2. .62 12.0e5 Barren or Sp20 15. .50 .92 10. 5. .60 9.0e25 Herbaceous 21 15. .50 .93 30. 5. .60 9.0e25 Wooded Tun22 15. .50 .92 15. 5. .60 9.0e25 Mixed Tundra23 25. .02 .85 10. 2. .62 12.0e5 Bare Ground 24 80. .95 .95 0.01 5. 0. 9.0e25 Snow or Ice

Eight-Hour Ozone Attainment Plan
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3.2.5 Initial Conditions - September 24-30, 1997

The MM5 simulation is initialized at 1200 UTC on September 24, 1997, and run 144

hours until 1200 UTC on September 30, 1997. Our experience with the August 3-7, 1997,

indicted that the EDAS data showed better results for Southern California than the GDAS and

NCEP/NCAR Reanalysis. We obtained from the National Center for Atmospheric Research

(NCAR) the NCEP Eta 212 Grid three dimensional and surface analysis data sets for September

1997. The NCEP EDAS are three-dimensional fields of meteorological variables at 40 km

spatial resolution analyzed every 3 hours. 

For sea surface temperature (SST) inputs we obtained SST data from the California

Institute of Technology Jet Propulsion Laboratory. After we modeled the August 4-7, 1997,

ozone episode, higher resolution sea surface temperature data became available. We obtained

the 4 km resolution SST data averaged for the eight day period, September 22-29, 1997. We

used the eight day averaged data set because the daily data have many spatial gaps due to cloud

cover. There are two eight day data sets, one for daytime SSTs and one for nighttime SSTs. We

applied the daytime SSTs at 12, 15, 18, 21, and 00 UTC and the nighttime SSTs at 03, 06, and 09

UTC.

The next steps in preparing the initial and boundary conditions and FDDA inputs are the

RAWINS/LITTLE_R and INTERP preprocessors. We obtained data files of rawinsonde upper

air observations and surface meteorological observations for September 24-30, 1997, from

NCAR. These data and the output files from REGRID were input into LITTLE_R. Output from

LITTLE_R are two dimensional fields of meteorological variables on pressure surfaces in the

grid cells of the MM5 horizontal grid domains.

As discussed above we used EDAS analyses as input to REGRID. We compared the

analyses created by REGRID and the analyses output by LITTLE_R using upper air and surface

observations. Because EDAS analyses are high resolution analyses we did not find that

LITTLE_R added any significant information to the MM5 initial and boundary conditions. For

this reason we skipped the LITTLE_R step and input REGRID analyses directly into the

INTERP preprocessor.

 The INTERP preprocessor interpolates the output from REGRID or

RAWINS/LITTLE_R vertically to the MM5 vertical coordinates. We used the same vertical

grid structure for MM5 as the August simulation. The 31 sigma levels at the top and bottom of

the 30 vertical layers are specified in Table 15.

3.2.6 MM5 Parameters and Four Dimensional Data Assimilation - September 24-30, 1997

The same MM5 parameters used for the August 3-7, 1997, modeling are used for the

September 24-30, 1997, period except for FDDA. For the September 24-30, 1997, MM5

modeling we did not use observational FDDA for temperature and moisture on the 5 km grid. 

This is based on a recommendation we received from a reviewer of our paper on the August

episode modeling (Wagner et al. 2005). The observational data set includes SCOS97 surface

Eight-Hour Ozone Attainment Plan
20

and radar wind profiler meteorological observations. The parameters used are indicated below

where the MM5 input stream for FDDA parameters is reproduced. When multiple values occur

on a line the first parameter value is for the 45 km domain, the second for the 15 km domain, and

the third for the 5 km domain.

;

 ; ************* 4DDA OPTIONS **********************

 ;

 ; THE FIRST DIMENSION (COLUMN) IS THE DOMAIN IDENTIFIER:

 ; COLUMN 1 = DOMAIN #1, COLUMN 2 = DOMAIN #2, ETC.

 ;

 ; START TIME FOR FDDA (ANALYSIS OR OBS) FOR EACH DOMAIN

 ; (IN MINUTES RELATIVE TO MODEL INITIAL TIME)

 FDASTA=0.,0.,0.,0.,0.,0.,0.,0.,0.,0.

 ; ENDING TIME FOR FDDA (ANALYSIS OR OBS) FOR EACH DOMAIN

 ; (IN MINUTES RELATIVE TO MODEL INITIAL TIME)

 FDAEND=8640.,8640.,8640.,0.,0.,0.,0.,0.,0.,0.,

 ;

 ; **************** ANALYSIS NUDGING ******************

 ;

 ; THE FIRST DIMENSION (COLUMN) OF THE ARRAYS DENOTES THE

 ; DOMAIN IDENTIFIER:

 ; COLUMN 1 = DOMAIN #1, COLUMN 2 = DOMAIN #2, ETC.

 ; THE SECOND DIMENSION (ROW OR LINE) EITHER REFERS TO THE 3D VS

 ; SFC ANALYSIS OR WHICH VARIABLE IS ACCESSED:

 ; LINE 1 = 3D, LINE 2 = SFC OR

 ; LINE 1 = U, LINE 2 = V, LINE 3 = T, LINE 4 = Q

 ;

 ; IS THIS A GRID 4DDA RUN? 0 = NO; 1 = YES

 I4D= 1,1,1,0,0,0,0,0,0,0,

 0,1,0,0,0,0,0,0,0,0,

 ;

 ; SPECIFY THE TIME IN MINUTES BETWEEN THE INPUT (USUALLY

 ; FROM INTERP) USED FOR GRID FDDA

 DIFTIM=180.,180.,180.,0.,0.,0.,0.,0.,0.,0., ; 3D ANALYSIS NUDGING

 180.,180.,180.,0.,0.,0.,0.,0.,0.,0., ; SFC ANALYSIS NUDGING

 ;

 ; GRID NUDGE THE WIND FIELD? 0 = NO; 1 = YES

 IWIND=1,1,1,0,0,0,0,0, ; 3D ANALYSIS NUDGING

 0,1,0,0,0,0,0,0,0, ; SFC ANALYSIS NUDGING

 ;

 ; NUDGING COEFFICIENT FOR WINDS ANALYSES

 GV=2.5E-4,2.5E-4,1.0E-4,0.,0.,0.,0.,0.,0.,0., ; 3D ANALYSIS NUDGING

 2.5E-4,2.5E-4,1.0E-4,0.,0.,0.,0.,0.,0.,0., ; SFC ANALYSIS NUDGING

 ;

 ; GRID NUDGE THE TEMPERATURE FIELD? 0 = NO; 1 = YES

 ITEMP=1,1,0,0,0,0,0,0,0,0, ; 3D ANALYSIS NUDGING

 0,0,0,0,0,0,0,0,0,0, ; SFC ANALYSIS NUDGING

 ;

Eight-Hour Ozone Attainment Plan
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 ; NUDGING COEFFICIENT FOR TEMPERATURE ANALYSES

 GT=2.5E-4,2.5E-4,1.0E-4,0.,0.,0.,0.,0.,0.,0., ; 3D ANALYSIS NUDGING

 2.5E-4,2.5E-4,1.0E-4,0.,0.,0.,0.,0.,0.,0., ; SFC ANALYSIS NUDGING

 ;

 ; GRID NUDGE THE MOISTURE FIELD? 0 = NO; 1 = YES

 IMOIS=1,1,0,0,0,0,0,0,0,0, ; 3D ANALYSIS NUDGING

 0,0,0,0,0,0,0,0,0,0, ; SFC ANALYSIS NUDGING

 ;

 ; NUDGING COEFFICIENT FOR THE MIXING RATIO ANALYSES

 GQ=1.E-5,1.E-5,1.0E-5,0.,0.,0.,0.,0.,0.,0., ; 3D ANALYSIS NUDGING

 1.E-5,1.E-5,1.0E-5,0.,0.,0.,0.,0.,0.,0., ; SFC ANALYSIS NUDGING

 ;

 ; GRID NUDGE THE ROTATIONAL WIND FIELD? 0 = NO; 1 = YES

 IROT=0,0,0,0,0,0,0,0,0,0, ; 3D ANALYSIS NUDGING

;

 ; NUDGING COEFFICIENT FOR THE ROTATIONAL COMPONENT OF THE WINDS

 GR=0.,0.,0.,0.,0.,0.,0.,0.,0.,0., ; 3D ANALYSIS NUDGING

 ;

 ; IF GRID NUDGING (I4D(1,1)=1) AND YOU WISH TO EXCLUDE THE

 ; BOUNDARY LAYER FROM FDDA OF COARSE GRID THREE DIMENSIONAL

 ; DATA (USUALLY FROM INTERP),

 ; 0 = NO, INCLUDE BOUNDARY LAYER NUDGING

 ; 1 = YES, EXCLUDE BOUNDARY LAYER NUDGING

 INONBL =1,0,0,0,0,0,0,0,0,0, ; U WIND

 1,0,0,0,0,0,0,0,0,0, ; V WIND

 1,1,1,1,1,1,1,1,1,1, ; TEMPERATURE

 1,1,1,1,1,1,1,1,1,1, ; MIXING RATIO

 ;

 ; RADIUS OF INFLUENCE FOR SURFACE ANALYSIS (KM).

 ; IF I4D(2,1)=1 OR I4D(2,2)=1, ETC, DEFINE RINBLW (KM) USED

 ; IN SUBROUTINE BLW TO DETERMINE THE HORIZONTAL VARIABILITY

 ; OF THE SURFACE-ANALYSIS NUDGING AS A FUNCTION OF SURFACE

 ; DATA DENSITY. OVER LAND, THE STRENGTH OF THE SURFACE-

 ; ANALYSIS NUDGING IS LINEARLY DECREASED BY 80 PERCENT AT

 ; THOSE GRID POINTS GREATER THAN RINBLW FROM AN OBSERVATION

 ; TO ACCOUNT FOR DECREASED CONFIDENCE IN THE ANALYSIS

 ; IN REGIONS NOT NEAR ANY OBSERVATIONS.

 RINBLW=250.,

 ;

 ; SET THE NUDGING PRINT FREQUENCY FOR SELECTED DIAGNOSTIC

 ; PRINTS IN THE GRID (ANALYSIS) NUDGING CODE (IN CGM

 ; TIMESTEPS)

 NPFG=1000,

 ;

 ; **************** OBSERVATION NUDGING ***************

 ;

 ;

 ; INDIVIDUAL OBSERVATION NUDGING. VARIABLES THAT ARE ARRAYS

 ; USE THE FIRST DIMENSION (COLUMN) AS THE DOMAIN IDENTIFIER:

Eight-Hour Ozone Attainment Plan
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 ; COLUMN 1 = DOMAIN #1, COLUMN 2 = DOMAIN #2, ETC.

 ;

 ; IS THIS INDIVIDUAL OBSERVATION NUDGING? 0 = NO; 1 = YES

 I4DI =0,1,1,0,0,0,0,0,0,0,

 ;

 ; OBS NUDGE THE WIND FIELD FROM STATION DATA? 0 = NO; 1 = YES

 ISWIND =1,1,1,0,0,0,0,0,0,0,

 ;

 ; NUDGING COEFFICIENT FOR WINDS FROM STATION DATA

 GIV =4.E-3,4.E-3,4.E-3,0.,0.,0.,0.,0.,0.,0.,

 ;

 ; OBS NUDGE THE TEMPERATURE FIELD FROM STATION DATA? 0 = NO; 1 = YES

 ISTEMP=0,0,0,0,0,0,0,0,0,0,

 ;

 ; NUDGING COEFFICIENT FOR TEMPERATURES FROM STATION DATA

 GIT =4.E-4,4.E-4,4.E-4,0.,0.,0.,0.,0.,0.,0.,

 ;

 ; OBS NUDGE THE MIXING RATIO FIELD FROM STATION DATA? 0 = NO; 1 = YES

 ISMOIS=0,0,0,0,0,0,0,0,0,0,

 ;

 ; NUDGING COEFFICIENT FOR THE MIXING RATIO FROM STATION DATA

 GIQ =4.E-4,4.E-4,4.E-4,0.,0.,0.,0.,0.,0.,0.,

 ;

 ; THE OBS NUDGING RADIUS OF INFLUENCE IN THE

 ; HORIZONTAL IN KM FOR CRESSMAN-TYPE DISTANCE-WEIGHTED

 ; FUNCTIONS WHICH SPREAD THE OBS-NUDGING CORRECTION

 ; IN THE HORIZONTAL.

 RINXY=30.,

 ;

 ; THE OBS NUDGING RADIUS OF INFLUENCE IN THE

 ; VERTICAL IN SIGMA UNITS FOR CRESSMAN-TYPE DISTANCE-

 ; WEIGHTED FUNCTIONS WHICH SPREAD THE OBS-NUDGING

 ; CORRECTION IN THE VERTICAL.

 RINSIG=0.001,

 ;

 ; THE HALF-PERIOD OF THE TIME WINDOW, IN MINUTES, OVER

 ; WHICH AN OBSERVATION WILL AFFECT THE FORECAST VIA OBS

 ; NUDGING. THAT IS, THE OBS WILL INFLUENCE THE FORECAST

 ; FROM TIMEOBS-TWINDO TO TIMEOBS+TWINDO. THE TEMPORAL

 ; WEIGHTING FUNCTION IS DEFINED SUCH THAT THE OBSERVATION

 ; IS APPLIED WITH FULL STRENGTH WITHIN TWINDO/2. MINUTES

 ; BEFORE OR AFTER THE OBSERVATION TIME, AND THEN LINEARLY

 ; DECREASES TO ZERO TWINDO MINUTES BEFORE OR AFTER THE

 ; OBSERVATION TIME.

 TWINDO=40.0,

 ;

 ; THE NUDGING PRINT FREQUENCY FOR SELECTED DIAGNOSTIC PRINT

 ; IN THE OBS NUDGING CODE (IN CGM TIMESTEPS)

 NPFI=1000,

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 ;

 ; FREQUENCY (IN CGM TIMESTEPS) TO COMPUTE OBS NUDGING WEIGHTS

 IONF=2,

 IDYNIN=0, ;for dynamic initialization using a ramp-down function to gradually

 ; turn off the FDDA before the pure forecast, set idynin=1 [y=1, n=0]

 DTRAMP=60.,;the time period in minutes over which the

 ; nudging (obs nudging and analysis nudging) is ramped down

 ; from one to zero. Set dtramp negative if FDDA is to be ramped

 ; down BEFORE the end-of-data time (DATEND), and positive if the

 ; FDDA ramp-down period extends beyond the end-of-data time.

 &END

3.2.7 Post Processing MM5 Outputs To CAMx Inputs

A post processor program mm5camx is available from Environ (2005) to convert MM5

output files to CAMx compatible meteorological input files. We used version 4.3 of this

program which was released on June 15, 2005.

Wheeler (2003) and others have suggested that the planetary boundary layer (PBL)

heights and subsequent vertical mixing parameters diagnosed from MM5 are inadequate for

stable and neutral conditions. The mm5camx post processing program mentioned above has

several algorithms to calculate the vertical mixing coefficients used in CAMx. This program,

mm5camx, uses the TKE (total kinetic energy) or the planetary boundary layer height output

from MM5 to make those calculations. Various other parameterizations are available for

estimating the vertical mixing coefficients or planetary boundary layer height. We chose to use

the profile approach in mm5camx and the parameterizations in the CALMET diagnostic

meteorological model (Scire et al. 2000) for re-diagnosing the planetary boundary layer height. 

We implemented this by running the CALMET model using the MM5 output as the only

observational input to CALMET. We used CALMET in the objective analysis mode and asked

CALMET to calculate planetary boundary layer heights (mixing heights). CALMET outputs

Pasquill-Gifford-Turner (PGT) stability classes which indicates if the atmospheric is stable,

neutral, or convective. The CALMET calculated mixing heights are substituted for the MM5

mixing height in the mm5camx program when calculating the vertical mixing coefficients using

the profile approach.

There is an additional postprocessor program, kvpatch, that can be run after mm5camx. 

This program replaces the vertical mixing parameter, Kv, in the lowest 100 m with a land use

dependent value if the value from mm5camx is below a minimum value. This procedure insures

that vertical mixing due to surface roughness occurs even if MM5 did not predict such mixing.

The program kvpatch has been used to prepare the vertical mixing coefficient for CAMx.

Eight-Hour Ozone Attainment Plan
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3.3 Air Quality

3.3.1 Photochemical Model Selection

Version 4.20 (ENVIRON 2005) of the. Comprehensive Air Quality Model with

Extensions (CAMx) with the SAPRC99 chemical mechanism was used for photochemical ozone

modeling in San Diego County. Model selection is discussed further in the protocol documents.

3.3.2 Modeling Domain

The SCOS97 modeling domain completely encompasses the South Coast Air Basin and

San Diego County, almost all of the South Central Coast Air Basin (excepting a small piece of

San Luis Obispo County), the California-Mexico border regions, and includes most of the inland

desert areas (Figure 3). This domain is chosen to eliminate the need to define boundary

concentrations between the air basins. The domain extends far enough offshore to contain wind

flow patterns conducive to over water recirculation. Vertically, the modeling domain extends to

a height of at least 5,000m AGL for a more complete representation of atmospheric processes. 

This will contain observed high ozone concentrations aloft and allow three-dimensional wind

flow patterns near elevated terrain features to be represented providing more accurate

representations of pollutant transport and recirculation. The CAMx grid domain is defined as:

• A Lambert Conformal map projection

• True latitudes of 30.0 degrees North and 60.0 degrees North

• A central longitude of 118.00 degree West

• The center of the projection is at 30.0 degrees North and 118.0 degrees West

• The origin of the grid (southwest corner of the southwest grid cell) is at -290000

m West and 225000 m North of the projection center in the Lambert map

projection

• A 116 cell east-west by 80 cell north-south grid with 5 km resolution

The first 20 layers above the surface in MM5 modeling domain are mapped directly into

the 20 layers of the CAMx grid. Thus, the MM5 sigma coordinate vertical structure defines the

CAMx vertical layers. Table 17 shows the sigma coordinate values and the pressure and height

of the layers in the MM5 reference atmosphere.

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Figure 3. Photochemical modeling domain.

Eight-Hour Ozone Attainment Plan
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Table 17. Vertical structure of the CAMx grid.

Layer Top and Bottom Layer Center

sigma Pressure

(Pa)

Height

(meters)

Layer 1⁄2 sigmas Pressure

(Pa)

Height

(meters)

0.423 48070 5502

0.464 51760 4982 20 0.4435 49915 5238

0.508 55720 4456 19 0.486 53740 4715

0.552 59680 3958 18 0.53 57700 4204

0.6 64000 3445 17 0.576 61840 3698

0.65 68500 2940 16 0.625 66250 3189

0.698 72820 2479 15 0.674 70660 2706

0.74 76600 2093 14 0.719 74710 2284

0.777 79930 1766 13 0.7585 78265 1928

0.814 83260 1450 12 0.7955 81595 1606

0.84 85600 1233 11 0.827 84430 1341

0.866 87940 1022 10 0.853 86770 1127

0.884 89560 878 9 0.875 88750 950

0.902 91180 737 8 0.893 90370 807

0.918 92620 613 7 0.91 91900 674

0.934 94060 490 6 0.926 93340 551

0.95 95500 369 5 0.942 94780 429

0.966 96940 249 4 0.958 96220 309

0.98 98200 146 3 0.973 97570 198

0.992 99280 58 2 0.986 98740 102

1 100000 0 1 0.996 99640 29

3.3.3 Initial and Boundary Condition Inputs

The initial and boundary conditions are specified as time and spatially invariant. We

used “clean” values to reduce the possible impact of boundary and initial conditions on future

year simulations. The initial and boundary concentrations are listed in Table 18. These initial

and boundary conditions are used for the 1997 baseline simulations and the 2002 and 2008

future year simulations.

The initial conditions are specified in CAMx at 0500 PDT on August 3, 1997, for the

August ozone episode. The initial conditions in all grid cells are set to the concentrations in

Table 18. The first day of the CAMx simulation, August 3, is used to “spin up” the simulation

Eight-Hour Ozone Attainment Plan
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from the “clean” background initial conditions. The simulation is run until 2300 PDT on

August 7.

The initial conditions are specified in CAMx at 0500 PDT on September 24, 1997, for the

September ozone episode. The initial conditions in all grid cells are set to the concentrations in

Table 18. The first two days of the CAMx simulation, September 24 and 25, are used to “spin

up” the simulation from the background initial conditions. The simulation is run until 0800 PDT

on September 29, 1997.

Table 18. Clean initial and boundary conditions for SAPRC99 species.

Species Concentration (ppm) Species Concentration (ppm)

NO 0.0000000 HC2H 0.0000000

NO2 0.0000000 CO2H 0.0000000

O3 0.0400000 CO3H 0.0000000

PAN 0.0000000 RC2H 0.0000000

PAN2 0.0000000 RC3H 0.0000000

MPAN 0.0000000 ACET 0.0000000

PBZN 0.0000000 MEK 0.0000000

NPHE 0.0000000 MEOH 0.0000000

RNO3 0.0000000 COOH 0.0000000

CRES 0.0000000 ROOH 0.0000000

DCB2 0.0000000 CO 0.2000000

DCB3 0.0000000 ETHE 0.0001800

HNO4 0.0000000 ALK1 0.0002000

BALD 0.0000000 ALK2 0.0007600

HONO 0.0000000 ALK3 0.0001900

XN 0.0000000 ALK4 0.0000000

 HCHO 0.0009300 ALK5 0.0007400

CCHO 0.0006700 ARO1 0.0004200

RCHO 0.0010100 ARO2 0.0001400

BACL 0.0000000 OLE1 0.0003600

PROD 0.0000000 OLE2 0.0000000

DCB1 0.0000000 NOXY 0.0000000

PHEN 0.0000000 SO2 0.0000000

ISOP 0.0000000 SULF 0.0000000

ISPD 0.0000000 HC2H 0.0000000

MVK 0.0000000 CO2H 0.0000000

METH 0.0000000 CO3H 0.0000000

MGLY 0.0000000 RC2H 0.0000000

GLY 0.0000000 RC3H 0.0000000

TERP 0.0000000 ACET 0.0000000

HNO3 0.0000000 MEK 0.0000000

HO2H 0.0000000 MEOH 0.0000000

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3.3.4 Ancillary Inputs

The Albedo/Haze/Ozone file specifies how these three photolysis-related parameters vary

in time and space for the CAMx simulation. Version 2 (October 2005) of Environ’s ahomap

program was used to prepare the file. The surface albedo was calculated based on the gridded

landuse data. The ozone column data were based on available satellite data from

http://toms.gsfc.nasa.gov/ozone/ozone_v8.html. 

The photolysis rates file determines the rates for chemical reactions in the mechanism

that are driven by sunlight. The photolysis rates file was prepared using version 4 of the

tropospheric ultraviolet-visible (TUV) radiative transfer model developed at NCAR with the

Albedo/Haze/Ozone file as input.

3.3.5 CAMx Model Options

CAMx has several user selectable options that are specified for each simulation through

the CAMx control file. The area preserving flux-form advection solver of Bott (BOTT option)

was used as the horizontal advection solver. For the atmospheric chemistry the CAMx Chemical

Mechanism Compiler (CMC) Fast Solver was used. The plume in grid option was not used for

the simulations. Dry deposition was used, but wet deposition was not used. The chemical

mechanism used is “mechanism 5" the SAPRC99 chemistry adapted for photochemical grid

modeling by selecting a specific “fixed parameter” lumping scheme. The ozone source

apportionment technology (OSAT) was used with most simulations.

4.0 EVALUATION OF MODEL PERFORMANCE

4.1 Emissions

The CAMx emission files are evaluated by graphical and tabular methods. Spatial plots

of the distribution of the ROG and NOx emissions were examined. Grid cell emissions were

summed to calculate total emissions for the domain. Changes in emission totals between August

and September and between 1997, 2002, and 2008 were examined. No unexplained patterns or

totals were found.

4.2 Evaluation of Meteorological Model Output

The model performance evaluation of MM5 focuses on the 5 km grid. We defined

subregional groups of sites for statistical model performance evaluation. The observation sites

are listed by mnemonic below. The locations of the stations are listed in an attachment to this

document.

SDCW: San Diego County West

VLYC VCEN SOLM SMPK SDOV SD12

SAND REDM RAMO PEND OCSD OCEA

LSF ESCO ESCD ECAJ DMMC CMPT 

CASE CARL BLKM ALPN ALPM

Eight-Hour Ozone Attainment Plan
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EAST: E San Diego/W Riverside

WSPR UCR TME2 THER TEME SRPL 

RANC PERR PALM OASS OAKG MTLG

LOST LELS KEEN JULI JPFT INDO 

FISH CMFS CATH BANN BANH APRT 

ANZA

ORNG: Orange County

TUST LHAB IRVI ELTR ELCR CMMV 

BELL ANAH

BORD: Mexican Border

TITT TIRP TIPL TILM SELY POTR 

OTAY MEXU MEXT MEXI MEXA MELO 

CLXE CLXC CHVT CALE BRWN

OFFS: Off Shore

SRIS SNI SCLM SCLH SCIS SBAR 

CLEM CATM CATI CATA BY54 BY23

PROF: All Profilers

VNS VLC VAF USC TTN TML 

TCL SMIP SCL SCE RSD PLM 

PHE PDE ONT NTN LAX LAS 

HPA GLA EMT ECO CBD BTW 

BFD APE

MM5 predicted surface wind speed, surface temperature, and PBL height are compared

to observed values and bias and error are calculated. Statistics are calculated for each day and

for each subregion separately. The bias and error for wind speed and temperature are compared

to some benchmarks proposed by Emery et al. (2001) for evaluating MM5 meteorological

modeling for air quality simulations. These benchmarks are:

Wind Speed Error #2 m/s Wind Speed Bias # ±0.5 m/s

Temperature Error #2 K Temperature Bias # ±0.5 K

Benchmarks have not been proposed for evaluating mixing heights.

Adjustments were not made to wind speed or temperature to account for any

discrepancies between the measurement heights and the MM5 model layer height. We compared

MM5 predictions for the first layer with surface observations. Some studies, Boucouvala et al. 

(2003), for example, have adjusted the MM5 predictions to the actual measurement height. The

mixing height observations are estimates from the Radar Wind Profiler/RASS systems. Wheeler

(2003) explains how these estimates were determined.

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4.2.1 August 4-7, 1997, Episode

A number of MM5 simulations were run for the August 3-7, 1997, period with various

adjustments in the MM5 model parameters and inputs. Model performance differences between

the runs were compared and used to make improvements to the simulation. In the end, outputs

from two separate MM5 simulations were used to prepare the meteorological inputs to CAMx. 

The final MM5 simulation had a few areas in the domain which exhibited “anomalous”

convection. This may be due to the FDDA of the surface temperature and moisture as discussed

above. This “anomalous” convection caused excessive vertical velocities that created problems

for CAMx. Our method to overcome this problem was to run MM5 without simulating water

vapor. This eliminated the “anomalous” convection and also slightly improved the wind fields. 

The meteorological inputs to CAMx were prepared with the wind fields from the “dry” run and

the cloud and water vapor fields from the “moist” run. So, although the momentum fields in

CAMx are dynamically consistent, the meteorological fields are not hydrodyamically consistent

since moisture is from a different MM5 simulation. This should not in itself cause any mass

consistency problems in CAMx.

The MM5 output for the 5 km domain is used for the comparison of prediction to

observation. The surface wind speed bias and error and the surface temperature bias and error

are listed for both the “moist” MM5 simulation and the “dry” MM5 simulation in the tables

below. Table 19 lists the bias and normalized bias for wind speed. Table 20 lists the error and

normalized error for wind speed. Table 21 lists the bias and normalized bias for temperature. 

Table 22 lists the error and normalized error for temperature. The tables are stratified by subregions and by day of the episode. The mixing height bias and error are listed for the “moist”

MM5 simulation, the “dry” MM5 simulation, and for the mixing heights calculated with the

CALMET model. Table 23 lists the bias and normalized bias for mixing height. Table 24 lists

the error and normalized error for mixing height. We used both these statistical measures and

subjective examination of graphical output to judge model performance.

The performance benchmark for wind speed bias is met for most areas on all days,

August 3-7. The “dry” simulation has the better model performance. The performance

benchmark for wind speed error is also met. Again, the “dry” simulation has slightly better

model performance. The surface temperature is mostly under predicted. Bias exceeds the

benchmark, especially on August 5. Error also exceeds the 2K benchmark much of the time,

although it rarely exceeds 4K. Performance for the “moist” and “dry” simulations is similar for

temperature. 

Eight-Hour Ozone Attainment Plan
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Table 19. Surface wind speed bias for August 3-7, 1997, for MM5 simulations.

Wind Speed Statistics

3-Aug-97 Mean Bias (m/s) Normalized Bias

Area Moist Dry Moist Dry

SDCW 0.4 0.2 0.52 0.36

EAST 0.0 -0.1 0.33 0.22

ORNG 0.6 0.3 0.82 0.67

BORD 0.0 -0.2 0.33 0.26

OFFS 0.5 0.3 0.79 0.70

4-Aug-97 Mean Bias (m/s) Normalized Bias

Area Moist Dry Moist Dry

SDCW 0.4 0.2 0.46 0.34

EAST 0.6 0.4 0.68 0.61

ORNG 0.6 0.4 0.86 0.75

BORD 0.9 0.8 1.03 0.87

OFFS 0.1 -0.1 0.75 0.62

5-Aug-97 Mean Bias (m/s) Normalized Bias

Area Moist Dry Moist Dry

SDCW 0.2 0.0 0.41 0.27

EAST 0.5 0.5 0.58 0.58

ORNG 0.6 0.4 0.94 0.79

BORD 0.5 0.4 0.72 0.63

OFFS 0.2 -0.1 0.81 0.62

6-Aug-97 Mean Bias (m/s) Normalized Bias

Area Moist Dry Moist Dry

SDCW 0.1 0.0 0.21 0.22

EAST 0.5 0.5 0.85 0.82

ORNG 0.5 0.4 0.89 0.79

BORD -0.1 -0.1 0.10 0.14

OFFS 0.1 -0.3 0.62 0.42

7-Aug-97 Mean Bias (m/s) Normalized Bias

Area Moist Dry Moist Dry

SDCW 0.3 0.2 0.41 0.29

EAST 0.3 0.4 0.39 0.44

ORNG 0.4 0.2 0.67 0.53

BORD -0.3 -0.3 0.02 0.05

OFFS 0.0 -0.3 0.45 0.29

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Table 20. Surface wind speed error for August 3-7, 1997, for MM5 simulations.

Wind Speed Statistics

3-Aug-97 Mean Error (m/s) Normalized Error

Area Moist Dry Moist Dry

SDCW 0.7 0.6 0.68 0.57

EAST 1.3 1.2 0.81 0.73

ORNG 0.8 0.7 0.95 0.89

BORD 1.1 1.1 0.61 0.59

OFFS 1.6 1.6 0.94 0.89

4-Aug-97 Mean Error (m/s) Normalized Error

Area Moist Dry Moist Dry

SDCW 0.7 0.6 0.65 0.55

EAST 1.3 1.2 1.04 1.00

ORNG 0.8 0.8 0.98 0.95

BORD 1.1 1.0 1.09 0.98

OFFS 1.7 1.7 0.97 0.87

5-Aug-97 Mean Error (m/s) Normalized Error

Area Moist Dry Moist Dry

SDCW 0.7 0.6 0.66 0.57

EAST 1.3 1.2 0.89 0.89

ORNG 1.0 1.0 1.13 1.08

BORD 1.0 0.9 0.91 0.84

OFFS 1.7 1.6 1.06 0.91

6-Aug-97 Mean Error (m/s) Normalized Error

Area Moist Dry Moist Dry

SDCW 0.6 0.6 0.50 0.51

EAST 1.4 1.4 1.22 1.15

ORNG 1.0 0.9 1.04 1.03

BORD 1.0 0.9 0.49 0.47

OFFS 1.5 1.5 0.96 0.87

7-Aug-97 Mean Error (m/s) Normalized Error

Area Moist Dry Moist Dry

SDCW 0.7 0.7 0.65 0.58

EAST 1.2 1.2 0.79 0.83

ORNG 0.8 0.8 0.88 0.84

BORD 1.0 1.0 0.46 0.45

OFFS 1.1 1.1 0.86 0.82

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Table 21. Surface temperature bias for August 3-7, 1997, for MM5 simulations.

Temperature Statistics

3-Aug-97 Mean Bias (K) Normalized Bias

Area Moist Dry Moist Dry

SDCW -1.7 -1.8 -0.05 -0.06

EAST -1.9 -1.6 -0.05 -0.04

ORNG -1.6 -1.4 -0.05 -0.04

BORD -0.2 0.1 0.00 0.01

OFFS -0.2 -0.2 0.05 0.05

4-Aug-97 Mean Bias (K) Normalized Bias

Area Moist Dry Moist Dry

SDCW -1.1 -1.7 -0.03 -0.05

EAST -0.5 -0.3 0.01 0.02

ORNG -0.8 -0.9 -0.02 -0.03

BORD 0.0 -0.9 0.00 -0.03

OFFS -0.3 -0.1 0.03 0.05

5-Aug-97 Mean Bias (K) Normalized Bias

Area Moist Dry Moist Dry

SDCW -1.8 -2.3 -0.04 -0.07

EAST -1.7 -1.3 -0.02 -0.01

ORNG -1.7 -1.8 -0.04 -0.06

BORD -1.0 -1.8 -0.02 -0.05

OFFS -2.6 -2.4 -0.06 -0.05

6-Aug-97 Mean Bias (K) Normalized Bias

Area Moist Dry Moist Dry

SDCW -0.9 -1.6 -0.02 -0.05

EAST -0.5 -0.4 0.00 0.01

ORNG -1.5 -2.2 -0.04 -0.07

BORD -0.3 -1.4 -0.01 -0.04

OFFS -1.4 -1.7 -0.01 -0.02

7-Aug-97 Mean Bias (K) Normalized Bias

Area Moist Dry Moist Dry

SDCW 1.2 0.2 0.05 0.01

EAST -0.1 -0.2 0.02 0.02

ORNG 0.7 -0.2 0.03 0.00

BORD 0.7 -0.2 0.02 -0.02

OFFS 1.5 1.6 0.10 0.11

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Table 22. Surface temperature error for August 3-7, 1997, for MM5 simulations.

Temperature Statistics

3-Aug-97 Mean Error (K) Normalized Error

Area Moist Dry Moist Dry

SDCW 2.2 2.3 0.08 0.08

EAST 3.4 3.4 0.11 0.12

ORNG 2.4 2.3 0.08 0.08

BORD 2.9 3.2 0.09 0.10

OFFS 3.5 3.6 0.19 0.19

4-Aug-97 Mean Error (K) Normalized Error

Area Moist Dry Moist Dry

SDCW 2.2 2.3 0.08 0.08

EAST 3.3 3.3 0.12 0.13

ORNG 2.3 2.3 0.08 0.08

BORD 1.9 1.9 0.07 0.06

OFFS 3.4 3.6 0.17 0.18

5-Aug-97 Mean Error (K) Normalized Error

Area Moist Dry Moist Dry

SDCW 2.9 3.0 0.10 0.10

EAST 3.9 3.8 0.13 0.13

ORNG 2.7 2.8 0.09 0.10

BORD 2.4 2.6 0.07 0.08

OFFS 4.6 4.5 0.18 0.17

6-Aug-97 Mean Error (K) Normalized Error

Area Moist Dry Moist Dry

SDCW 2.5 2.5 0.09 0.09

EAST 3.2 3.2 0.11 0.12

ORNG 2.7 3.1 0.09 0.11

BORD 2.2 3.2 0.07 0.10

OFFS 4.1 4.2 0.17 0.17

7-Aug-97 Mean Error (K) Normalized Error

Area Moist Dry Moist Dry

SDCW 1.7 1.6 0.07 0.07

EAST 3.3 3.0 0.12 0.11

ORNG 2.1 2.1 0.08 0.08

BORD 1.7 2.1 0.06 0.07

OFFS 2.3 2.3 0.13 0.14

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Mixing heights are under predicted by both the “moist” and “dry” MM5 simulations. 

Both MM5 simulations predict approximately the same mixing heights. MM5 mixing heights

range from a 168m under prediction bias on the 3rd to a 327m under prediction bias on the 5th. 

CALMET is successful in reducing the bias in the mixing heights. Bias is reduced to less than

100m on the 3rd and 6th and to less than 25m on the 4th, 5th, and 7th. However, the CALMET

mixing height errors are somewhat larger than the MM5 mixing height errors. Where MM5

mixing heights have errors ranging from 300m to 400m, the CALMET mixing height errors are

generally between 400m and 500m. MM5 mixing heights are near zero near the coast and Salton

sea. This does not agree with the observations and does not allow for sufficient vertical mixing

of emissions in the CAMx model. Figure 4 shows a spatial plot of MM5 predicted mixing height

for 1000 PDT on August 5, 1997. CALMET estimates higher mixing heights along the coast

and near the Salton sea as seen in Figure 5.

The examination of the spatial and temporal plots of the wind speeds, wind directions,

surface temperature, and mixing heights shows patterns that generally agree with the

observations.

Table 23. Mixing height bias for August 3-7, 1997, for MM5 simulations.

Mixing Height Statistics

3-Aug-97 Mean Bias (m) Normalized Bias

Area Moist Dry CALMET Dry Moist Dry CALMET Dry

PROF -172.4 -168.4 84.7 -0.39 -0.39 0.25

4-Aug-97 Mean Bias (m) Normalized Bias

Area Moist Dry CALMET Dry Moist Dry CALMET Dry

PROF -259.2 -256.4 -12.3 -0.6 -0.59 0.04

5-Aug-97 Mean Bias (m) Normalized Bias

Area Moist Dry CALMET Dry Moist Dry CALMET Dry

PROF -327.2 -322.4 -22.1 -0.66 -0.66 0.11

6-Aug-97 Mean Bias (m) Normalized Bias

Area Moist Dry CALMET Dry Moist Dry CALMET Dry

PROF -311.1 -315.6 -98.2 -0.61 -0.63 -0.10

7-Aug-97 Mean Bias (m) Normalized Bias

Area Moist Dry CALMET Dry Moist Dry CALMET Dry

PROF -186.6 -187 21.9 -0.49 -0.49 0.11

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Table 24. Mixing height error for August 3-7, 1997, for MM5 simulations.

Mixing Height Statistics

3-Aug-97 Mean Error (m) Normalized Error

Area Moist Dry CALMET Dry Moist Dry CALMET Dry

PROF 291.8 305.6 404.6 0.7 0.74 1.00

4-Aug-97 Mean Error (m) Normalized Error

Area Moist Dry CALMET Dry Moist Dry CALMET Dry

PROF 319.5 318.4 401.4 0.76 0.75 0.99

5-Aug-97 Mean Error (m) Normalized Error

Area Moist Dry CALMET Dry Moist Dry CALMET Dry

PROF 375 380.5 484.6 0.8 0.81 1.13

6-Aug-97 Mean Error (m) Normalized Error

Area Moist Dry CALMET Dry Moist Dry CALMET Dry

PROF 392.6 387.4 406.5 0.81 0.8 0.90

7-Aug-97 Mean Error (m) Normalized Error

Area Moist Dry CALMET Dry Moist Dry CALMET Dry

PROF 308.2 294.4 378.9 0.82 0.78 1.04

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Figure 4. Mixing height (meters) from MM5 output.

Figure 5. Mixing height (meters) from CALMET output.

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4.2.2 September 27-28, 1997, Episode 

Several MM5 simulations were made for the September 24-30, 1997, period with various

adjustments in the MM5 model parameters and inputs. Unlike the August episode MM5

simulation, “anomalous” convection was not present which may be due to no “nudging” toward

surface moisture and temperature. A single MM5 simulation is used to prepare CAMX

meteorological inputs.

Statistical model performance is discussed below. The tables are stratified by the subregions defined in Section 4.2. Table 25 lists the bias and normalized bias for surface wind

speed. Table 26 lists the error and normalized error for wind speed. Table 27 lists the bias and

normalized bias for surface temperature. Table 28 lists the error and normalized error for

temperature. Table 29 lists the bias and normalized bias for mixing height. Table 30 lists the

error and normalized error for mixing height for both the MM5 simulation and the CALMET

mixing height estimates.

Except for September 25 most of the sub-regions meet the performance benchmarks for

wind speed bias. Wind speed is mostly over predicted. All days and sub-regions meet the

benchmark for wind speed error.

 Surface temperature is generally over predicted with only a few instances of meeting the

benchmark. Surface temperature errors are from 2K to 4K with only a few instances of meeting

the benchmark.

MM5 underestimates the mixing heights with bias ranging from -235m to -303m. 

CALMET mixing height estimates have lower bias, with under predictions ranging from -58m to 

-77m. MM5 mixing height errors range from 282m to 358m. CALMET mixing height errors

are slightly larger than for MM5 with the CALMET mixing errors ranging from 341m to 380m. 

As with August 3-7, 1997, for September 24-29, 1997, CALMET does better with estimating the

coastal area mixing heights than MM5

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Table 25. Surface wind speed bias for September 24-29, 1997, MM5 simulations.

Wind Speed Statistics

24-Sep-97

Area Mean Bias (m/s) Normalized Bias

SDCW 1.3 0.74

EAST 0.5 0.29

ORNG 0.1 0.37

BORD 0.5 0.36

OFFS 0.1 0.54

25-Sep-97

Area Mean Bias (m/s) Normalized Bias

SDCW 0.6 0.41

EAST -0.1 0.11

ORNG 0.6 0.28

BORD 1.4 0.61

OFFS 0.9 0.64

26-Sep-97

Area Mean Bias (m/s) Normalized Bias

SDCW 0.4 0.44

EAST 0.6 0.82

ORNG 0.6 0.63

BORD 0.4 0.37

OFFS 0.0 0.37

27-Sep-97

Area Mean Bias (m/s) Normalized Bias

SDCW 0.2 0.39

EAST 0.4 0.47

ORNG 0.2 0.22

BORD 0.3 0.42

OFFS 0.2 0.82

28-Sep-97

Area Mean Bias (m/s) Normalized Bias

SDCW -0.1 0.13

EAST 0.7 0.67

ORNG 0.4 0.37

BORD 0.3 0.33

OFFS -0.1 0.46

29-Sep-97

Area Mean Bias (m/s) Normalized Bias

SDCW 0.1 0.10

EAST 0.1 0.33

ORNG 0.2 0.22

BORD 0.1 0.13

OFFS -0.2 0.41

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Table 26. Surface wind speed error for September 24-29, 1997, MM5 simulations.

Wind Speed Statistics

24-Sep-97

Area Mean Error (m/s) Normalized Error

SDCW 1.7 0.84

EAST 1.4 0.58

ORNG 0.9 0.84

BORD 1.1 0.58

OFFS 1.2 0.87

25-Sep-97

Area Mean Error (m/s) Normalized Error

SDCW 1.2 0.56

EAST 1.4 0.54

ORNG 0.8 0.37

BORD 1.4 0.62

OFFS 1.3 0.72

26-Sep-97

Area Mean Error (m/s) Normalized Error

SDCW 0.7 0.62

EAST 1.2 1.05

ORNG 0.9 0.77

BORD 0.9 0.61

OFFS 1.5 0.61

27-Sep-97

Area Mean Error (m/s) Normalized Error

SDCW 0.7 0.66

EAST 1.1 0.80

ORNG 0.7 0.55

BORD 0.7 0.62

OFFS 1.1 1.10

28-Sep-97

Area Mean Error (m/s) Normalized Error

SDCW 0.6 0.54

EAST 1.2 0.91

ORNG 0.7 0.60

BORD 0.6 0.70

OFFS 1.0 0.83

29-Sep-97

Area Mean Error (m/s) Normalized Error

SDCW 0.6 0.46

EAST 0.9 0.77

ORNG 0.8 0.54

BORD 0.6 0.55

OFFS 0.9 0.78

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Table 27. Surface temperature bias for September 24-29, 1997, MM5 simulations.

Temperature Statistics

24-Sep-97

Area Mean Bias (K) Normalized Bias

SDCW 0.8 0.05

EAST -0.7 0.04

ORNG 2.7 0.11

BORD 0.6 0.03

OFFS 1.1 0.06

25-Sep-97

Area Mean Bias (K) Normalized Bias

SDCW 3.8 0.20

EAST 1.0 0.06

ORNG 2.4 0.11

BORD 3.1 0.14

OFFS 0.4 0.03

26-Sep-97

Area Mean Bias (K) Normalized Bias

SDCW 0.4 0.03

EAST 0.8 0.05

ORNG 0.4 0.02

BORD 1.4 0.06

OFFS 0.0 0.05

27-Sep-97

Area Mean Bias (K) Normalized Bias

SDCW 0.2 0.03

EAST 1.6 0.14

ORNG -0.4 0.00

BORD 0.6 0.04

OFFS -0.5 0.03

28-Sep-97

Area Mean Bias (K) Normalized Bias

SDCW 0.4 0.03

EAST 0.2 0.05

ORNG -0.5 -0.01 

BORD 0.1 0.02

OFFS -2.2 -0.06 

29-Sep-97

Area Mean Bias (K) Normalized Bias

SDCW 0.8 0.05

EAST 1.2 0.11

ORNG -0.6 -0.02 

BORD 0.6 0.05

OFFS -1.2 -0.03 

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Table 28. Surface temperature error for September 24-29, 1997, MM5 simulations.

Temperature Statistics

24-Sep-97

Area Mean Error (K) Normalized Error

SDCW 3.7 0.15

EAST 4.2 0.23

ORNG 2.8 0.11

BORD 3.6 0.13

OFFS 3.3 0.14

25-Sep-97

Area Mean Error (K) Normalized Error

SDCW 3.9 0.21

EAST 2.2 0.11

ORNG 2.6 0.11

BORD 3.2 0.15

OFFS 1.6 0.08

26-Sep-97

Area Mean Error (K) Normalized Error

SDCW 1.1 0.06

EAST 2.0 0.11

ORNG 1.3 0.06

BORD 1.8 0.08

OFFS 3.2 0.15

27-Sep-97

Area Mean Error (K) Normalized Error

SDCW 1.8 0.09

EAST 3.2 0.20

ORNG 1.8 0.08

BORD 1.8 0.08

OFFS 3.6 0.16

28-Sep-97

Area Mean Error (K) Normalized Error

SDCW 2.1 0.09

EAST 3.9 0.17

ORNG 2.3 0.10

BORD 2.3 0.09

OFFS 4.0 0.16

29-Sep-97

Area Mean Error (K) Normalized Error

SDCW 1.9 0.09

EAST 3.8 0.20

ORNG 2.1 0.09

BORD 2.2 0.10

OFFS 2.9 0.12

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Table 29. Mixing height bias for September 26-29, 1997, MM5 simulations.

Mixing Height Statistics

26-Sep-97 Mean Bias (meters) Normalized Bias

Area MM5 CALMET MM5 CALMET

PROF -260.9 -58 -0.57 -0.03

27-Sep-97 Mean Bias (meters) Normalized Bias

Area MM5 CALMET MM5 CALMET

PROF -235.2 -59.7 -0.63 -0.16

28-Sep-97 Mean Bias (meters) Normalized Bias

Area MM5 CALMET MM5 CALMET

PROF -303 -76.8 -0.72 -0.08

29-Sep-97 Mean Bias (meters) Normalized Bias

Area MM5 CALMET MM5 CALMET

PROF -258.5 -66.7 -0.65 -0.18

Table 30. Mixing height error for September 26-29, 1997, for MM5 simulations.

Mixing Height Statistics

26-Sep-97 Mean Error (meters) Normalized Error

Area MM5 CALMET MM5 CALMET

PROF 357.7 358.6 0.77 0.92

27-Sep-97 Mean Error (meters) Normalized Error

Area MM5 CALMET MM5 CALMET

PROF 281.9 303.2 0.72 0.83

28-Sep-97 Mean Error (meters) Normalized Error

Area MM5 CALMET MM5 CALMET

PROF 340 380 0.8 0.98

29-Sep-97 Mean Error (meters) Normalized Error

Area MM5 CALMET MM5 CALMET

PROF 317.7 340.8 0.79 0.85

4.3 Evaluation of Air Quality Model Outputs for the Base Year August 4-7, 1997, Episode

EPA guidance recommends statistical and other analytical techniques to be part of an

operational evaluation of ozone model performance. The guidance recommends three statistical

measures be calculated for hourly ozone and 8 hourly ozone over the episode days in an

attainment demonstration. Model predictions are paired in time and space with observations for

these statistical measures. The model predictions at the observational site are bi-linearly

interpolated from the four grid cells surrounding the station location.

• Mean Normalized Bias - EPA (2005, Equation 15.1)

• Mean Normalized Gross Error - EPA (2005, Equation 15.2)

• Average Peak Prediction Bias and Error - as above except applied to daily

maxima at each monitoring location

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In addition we evaluated the ability of the model to predict the unmatched peak ozone in

San Diego County: Modelmax/Observedmax , where the modeled value occurred anywhere in the

county and the observed value occurred at the location of the observed daily maximum in San

Diego County. The statistics were calculated with a threshold value of 60 ppb to avoid undue

weighting of low ozone concentrations.

The modeling protocol established the following goals for the statistical model

performance. The same performance goals are used for both one-hour and eight-hour averaged

ozone. 

• unpaired peak accuracy to within ±20%

• paired normalized bias to within ±15%

• paired normalized error to within 35%

Sixteen surface ozone monitoring stations operated in San Diego County during

SCOS97. The names and mnemonics of these sites are listed in Table 31 and shown in Figure 6. 

The more densely populated areas of San Diego County are shown with shading in the figure. 

Supplemental sites that are not part of the normal monitoring network are indicated in Table 31.

Table 31. Ozone monitoring sites in San Diego County.

Site Mnemonic Site Mnemonic

Alpine ALPN 12th Street SD12

Chula Vista CHVT Black Mountain*^ BLKM

Del Mar DMMC Camp Pendleton PEND

El Cajon ECAJ Red Mountain*^ REDM

Escondido ESCO San Marcos Peak*^ SMPK

Oceanside OCEA Soledad Mountain*^ SOLM

Otay Mesa OTAY Valley Center* VCEN

Overland SDOV Warner Springs* WSPR

*Supplemental monitoring site.

^Site located on elevated terrain.

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Figure 6. Ozone monitoring sites in San Diego County, SCOS97.Eight-Hour Ozone Attainment Plan
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4.3.1 Evaluation of One-Hour Ozone Predictions

One-hour predicted ozone in San Diego meets many of the performance goals except for

over predicting peak ozone on August 6 and 7 and on August 4 the one-hour averaged ozone is

under predicted so the bias misses the performance goal. Table 32 lists the statistical model

performance measures for August 4 to 7.

Table 32. One-hour averaged ozone model performance for San Diego County for the August

4-7, 1997, ozone episode.

Episode Day Unpaired

Normalized Peak

(%)

Normalized

Bias 

(%)

Normalized

Error 

(%)

Normalized

Peak Bias

(%)

Normalized

Peak Error

(%)

August 4

(Peak location)

-14

Black Mtn

-21 28 -9 18

August 5

(Peak location)

-1

Otay Mesa

-4 23 -5 15

August 6

(Peak location)

22

Valley Center

4 16 -1 11

August 7

(Peak location)

30

Warner Springs

14 19 30 31

Figures 7a and 7b show time series of one-hour averaged ozone and NOx predictions and

observations at 16 monitoring sites in San Diego County for August 3 to 7. Figures 8a to 8d

show the daily one-hour maximum grid cell predicted values and the daily maximum observed

ozone for August 4 to 7. 

Alpine is the location of the only monitoring in San Diego County not in attainment of

the 8 hour averaged ozone standard. At Alpine hourly ozone is reasonably well predicted on

August 4 and 5 and on August 6 until about noon. After that time hourly ozone is over predicted

at Alpine. Ozone at the coastal sites of Camp Pendleton, Oceanside, and Del Mar is slightly

over predicted during August 4 to 7. The San Diego 12th Street and Chula Vista sites’ ozone is

predicted on all days. The San Diego Overland site ozone is under predicted on the 4th, predicted

on the 5th and over predicted on the 6th and 7th. Ozone at Otay Mesa is predicted through August

5, then over predicted at night and on August 7. The inland site Escondido ozone is predicted

well on the 3rd to 6th, but over predicted on the 7th. The inland site El Cajon ozone is predicted

well on the 3rd to 5th, but over predicted on the 6th and 7th. The Valley Center site ozone is over

predicted at night and on the 7th, but predicted during the day on August 4, 5, and 6. The ozone

predictions at Warner Springs are out of phase with the predicted peaks, which occur six to eight

hours after the observed ozone peaks. At the elevated sites Black Mountain and Red Mountain

the nocturnal ozone peak which occurs between August 3 and 4 is not predicted. Ozone is

predicted fairly well on the remaining days at Red Mountain. Ozone at Black Mountain is

predicted well on August 4 and 5, but is over predicted on August 6 and 7. Ozone is predicted

Eight-Hour Ozone Attainment Plan
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fairly well at San Marcos Peak and Soledad Mountain on August 3 to 5, but is over predicted on

August 6 and 7. 

The spatial plot of peak ozone for August 4 shows the observed lower ozone

concentrations near the coast and higher values inland in San Diego County are predicted by the

simulations. The peak predicted values extend south from Alpine into Mexico. On August 5

there are two areas of observed maximum ozone in San Diego County; one in the northwest part

of the county and another in the southwest part. The northwest area is predicted well. The

predicted ozone in the southwest part of the county does not extend westward far enough toward

the coast so that Chula Vista, Otay Mesa, and 12th Street are under predicted. Peak predicted

ozone on August 6 in San Diego County is located northeast of Alpine with higher

concentrations extending north and south from that area. This area of predicted peak ozone is

not located far enough eastward, which causes the observed ozone maxima to be over predicted. 

The same pattern is seen in the ozone predictions on August 7, with the predicted maximum not

far enough east of the coast, so again, the inland observed ozone maxima are over predicted.

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Figure 7a. Time series of one-hour averaged ozone and NOx in San Diego County, August 3-7,

1997.

Eight-Hour Ozone Attainment Plan
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Figure 7b. Time series of one-hour averaged ozone and NOx in San Diego County, August 3-7,

1997.

Eight-Hour Ozone Attainment Plan
50

Figure 8a. Plot of maximum predicted one-hour averaged ozone for August 4, 1997.

Figure 8b. Plot of maximum predicted one-hour averaged ozone for August 5, 1997.

Eight-Hour Ozone Attainment Plan
51

Figure 8c. Plot of maximum predicted one-hour averaged ozone for August 6, 1997.

Figure 8d. Plot of maximum predicted one-hour averaged ozone for August 7, 1997.

Eight-Hour Ozone Attainment Plan
52

4.3.2 Evaluation of Eight-Hour Ozone Predictions

Eight-hour predicted ozone in San Diego meets many of the performance goals except for

over predicting peak ozone on August 6 and 7 and on August 4 eight-hour averaged ozone is

under predicted and the bias misses the performance goal. Table 33 lists the statistical model

performance measures for August 4 to 7.

Table 33. Eight-hour averaged ozone model performance for San Diego County for the August

4-7. 1997, ozone episode.

Episode Day Unpaired

Normalized Peak

(%)

Normalized

Bias 

(%)

Normalized

Error 

(%)

Normalized

Peak Bias

(%)

Normalized

Peak Error

(%)

August 4

(Peak location)

-12

Black Mtn

-20 23 -6 13

August 5

(Peak location)

7

Red Mtn

1 16 6 11

August 6

(Peak location)

26

Alpine

9 15 11 11

August 7

(Peak location)

27

Warner Springs

774 4

Figures 9a and 9b show time series of eight-hour averaged ozone predictions and

observations at 16 monitoring sites in San Diego County for August 3 to 7. Figures 10a to 10d

show the daily eight-hour maximum predicted and observed ozone in the modeling domain for

August 4 to 7. 

Alpine is the location of the only monitoring in San Diego County not in attainment of

the eight-hour averaged ozone standard. Eight-hour averaged ozone is reasonably well predicted

on August 4 and 5. After that eight-hour averaged ozone is over predicted at Alpine. Nearer the

coast, El Cajon ozone is over predicted, especially on August 6 and 7. The San Diego Overland

site ozone is predicted on August 4 and 5, but over predicted on August 6 and 7. Ozone at the

San Diego 12th Street is predicted on August 4 and 5, but the flat trend on August 6 is not

predicted. At the coastal sites of Del Mar, Oceanside and Pendleton ozone is over predicted. 

Escondido ozone is predicted on August 4, but is over predicted on August 5, 6, and 7. Red

Mountain ozone is predicted well from the 4th through noon on the 6th and then over predicted. 

At Black Mountain nocturnal ozone peaks are not predicted. The August 5 afternoon ozone peak

is predicted, but the afternoon peaks on August 6 and 7 are over predicted. Ozone at Chula Vista

is predicted on August 4, 5, and 7, but is over predicted on August 6. At Otay Mesa afternoon

ozone is predicted on August 5 and 6, but over predicted on August 4 and 7 and at night on

August 5 and 6. At San Marcos Peak ozone is under predicted at night August 4 to 5, but out of

phase for the observed nocturnal peak ozone August 5 to 6 and August 6 to 7. Ozone at Valley

Center is over predicted. Predicted zone at Warner Springs is out of phase with observed ozone.

Eight-Hour Ozone Attainment Plan
53

The same spatial pattern seen in the one-hour averaged ozone is observed in the eighthour averaged ozone. The spatial plot of peak ozone for August 4 shows the observed lower

ozone concentrations near the coast and higher values inland are predicted by the simulation. 

The peak predicted values extend south from Alpine into Mexico. On August 5 there are two

areas of maximum ozone in San Diego County; one in the northwest part of the county and

another in the southwest part. The northwest area is slightly over predicted. The predicted

ozone in the southwest part of the county is predicted well. Peak predicted ozone on August 6 in

San Diego County is located northeast of Alpine with higher concentrations extending north and

south from that area. This area of predicted peak ozone is not located far enough eastward which

causes the observed ozone maxima to be over predicted. The same pattern is seen in the ozone

predictions on August 7 with the predicted maximum not far enough east of the coast, so again,

the inland observed ozone maxima are over predicted.

Eight-Hour Ozone Attainment Plan
54

Figure 9a. Time series of eight-hour averaged ozone in San Diego County, August 3-7, 1997.

Eight-Hour Ozone Attainment Plan
55

Figure 9b. Time series of eight-hour averaged ozone in San Diego County, August 3-7, 1997. 

Figure 10a. Plot of maximum predicted eight-hour averaged ozone for August 4, 1997.

Eight-Hour Ozone Attainment Plan
56

Figure 10b. Plot of maximum predicted eight-hour averaged ozone for August 5, 1997.

Figure 10c. Plot of maximum predicted eight-hour averaged ozone for August 6, 1997.

Eight-Hour Ozone Attainment Plan
57

Figure 10d. Plot of maximum predicted eight-hour averaged ozone for August 7, 1997.

4.4 Evaluation of Air Quality Model Outputs for the Base Year September 27-28, 1997, Episode

4.4.1 Evaluation of One-Hour Ozone Predictions

One-hour predicted ozone in San Diego County meets most of the performance goals

except bias on both September 27 and 28 when ozone is under predicted. Table 34 lists the

statistical model performance measures for September 27 and 28. Model performance is

improved if the supplemental monitoring sites on elevated terrain are excluded. These would be

sites: Black Mountain, Red Mountain, San Marcos Peak, and Soledad Mountain. These sites are

impacted by ozone aloft, which remains high at night in the observations, but is lower in the

simulation. Statistical performance for the remaining set of monitoring sites is shown in Table

35.

Statistical model performance for one-hour averaged ozone with all monitoring sites does

not meet the performance goals for bias with both September 27th and 28th ozone under predicted. 

When the sites on elevated terrain are excluded most of the performance goals are met except for

an under prediction bias on September 28, which misses the performance goal.

Eight-Hour Ozone Attainment Plan
58

Table 34. One-hour averaged ozone model performance for San Diego County for the

September 27-28, 1997, ozone episode.

Episode Day Unpaired

Normalized

Peak (%)

Normalized

Bias 

(%)

Normalized

Error 

(%)

Normalized

Peak Bias (%)

Normalized

Peak Error

(%)

September 27

(Peak location)

-11

San Marcos Pk

-18 21 -16 16

September 28

(Peak location)

-13

Black Mtn

-26 31 -16 21

Table 35. One-hour averaged ozone model performance for San Diego County for the

September 27-28, 1997, ozone episode excluding elevated sites.

Episode Day Unpaired

Normalized

Peak (%)

Normalized

Bias 

(%)

Normalized

Error 

(%)

Normalized

Peak Bias (%)

Normalized

Peak Error

(%)

September 27

(Peak location)

6

Overland

-7 11 -11 12

September 28

(Peak location)

-13

Alpine

-19 26 -12 20

Figures 11a and 11 b show time series of one-hour averaged ozone and NOx predictions

and observations at 16 monitoring sites in San Diego County for September 26-28. Figures 12a

to 12c show the daily one-hour maximum predicted and observed ozone in the modeling domain

for September 26 to 29.

Alpine is the location of the only monitoring in San Diego County not in attainment of

the 8 hour averaged ozone standard. Hourly ozone is reasonably well predicted on September 27

but is under predicted on September 28. At night ozone is over predicted from the 26th to the

27th. El Cajon ozone is predicted on the 26th and 27th, but the peak is predicted late on the 28th. 

At the coastal site of Del Mar ozone is predicted on the 26th and 27th, but is over predicted on the

28th. At coastal sites Oceanside and Pendleton ozone is predicted during the day, but over

predicted at night. In southern San Diego County at Otay Mesa and Chula Vista, ozone is

predicted on the 26th and 27th, but under predicted on the 28th. Ozone at Escondido is predicted

on the 26th and 27th, but under predicted on the 28th. At the San Diego 12th Street site ozone is

predicted except for an under prediction during the night between the 27th and 28th. The San

Diego Overland site ozone is predicted during the day, but over predicted at night. At the

elevated site Black Mountain ozone is predicted until noon on the 27th, then is under predicted. 

At Red Mountain and San Marcos Peak ozone is predicted on the 26th, but under predicted on the

27th and 28th. Predicted ozone at Valley Center and Warner Springs has little diurnal variation

while the observed ozone shows a nocturnal minimum which is over predicted.

The spatial pattern of observed one-hour averaged peak ozone on September 26 is fairly

uniform across San Diego County except for Warner Springs which has higher ozone. The

Eight-Hour Ozone Attainment Plan
59

pattern of predicted ozone is an area of higher ozone offshore and a second area in mid San

Diego County. The predicted values are close to the observed values except for Warner Springs. 

On September 27 observed ozone is higher at the elevated sites. Predicted ozone shows a ridge

line of higher ozone extending south from the Escondido into Mexico. The predicted values

along this ridge are similar to the observed values. Observed ozone on September 28 has higher

concentrations inland. The predicted ozone has a region of higher concentrations just offshore

and a second region of higher ozone near Alpine. The region near Alpine is not as large in

extent as the region of observed peak ozone.

Eight-Hour Ozone Attainment Plan
60

Figure 11a. Time series of one-hour averaged ozone and NOx in San Diego County, September

26-29, 1997.

Eight-Hour Ozone Attainment Plan
61

Figure 11b. Time series of one-hour averaged ozone and NOx in San Diego County, September

26-29, 1997.

Eight-Hour Ozone Attainment Plan
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Figure 12a. Plot of maximum predicted one-hour averaged ozone for September 26, 1997.

Figure 12b. Plot of maximum predicted one-hour averaged ozone for September 27, 1997.

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63

Figure 12c. Plot of maximum predicted one-hour averaged ozone for September 28, 1997.

4.4.2 Evaluation of Eight-Hour Ozone Predictions

Eight-hour predicted ozone in San Diego meets most of the performance goals except

bias on both September 27 and 28 when ozone is under predicted. Table 36 lists the statistical

model performance measures for September 27 and 28. Model performance is improved if the

supplemental monitoring sites on elevated terrain are excluded. All of the performance goals are

met except for bias on September 28 if the elevated sites are excluded as seen in Table 37.

Table 36. Eight-hour averaged ozone model performance for San Diego County for the

September 27-28, 1997, ozone episode.

Episode Day Unpaired

Normalized

Peak (%)

Normalized

Bias 

(%)

Normalized

Error 

(%)

Normalized

Peak Bias (%)

Normalized

Peak Error

(%)

September 27

(Peak location)

-18

Black Mtn

-24 25 -9 12

September 28

(Peak location)

-6

Alpine

-23 25 -11 15

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64

Table 37. Eight-hour averaged ozone model performance for San Diego County for the

September 27-28, 1997, ozone episode excluding elevated sites.

Episode Day Unpaired

Normalized

Peak (%)

Normalized

Bias 

(%)

Normalized

Error 

(%)

Normalized

Peak Bias (%)

Normalized

Peak Error

(%)

September 27

(Peak location)

5

Alpine

-2 5 -2 6

September 28

(Peak location)

-6

Alpine

-18 20 -10 14

Figures 13a and 13b show time series of eight-hour averaged ozone predictions and

observations at 16 monitoring sites in San Diego County for September 26-28. Figures 14a to

14c show the daily eight-hour maximum predicted and observed ozone in the modeling domain

for September 26 to 28.

Alpine is the location of the only monitoring in San Diego County not in attainment of

the 8 hour averaged ozone standard. Eight-hour averaged ozone is reasonably well predicted on

September 27 but is under predicted on September 28 and over predicted at night September 26

to 27. To the west, at El Cajon and San Diego Overland ozone is predicted except for over

prediction during the night September 27-28. Ozone at the San Diego 12th Street site is predicted

except for under prediction during the night September 27 to 28. At the coastal sites of

Oceanside and Pendleton ozone is predicted during the day, but over predicted at night. At the

coastal site in Del Mar, ozone is predicted September 26 and 27, but over predicted on

September 28. Inland at Escondido ozone is over predicted at night and under predicted on the

28th. At Otay Mesa ozone is over predicted on September 26 and 27 and under predicted on the

28th. Ozone at the elevated sites of Red Mountain, Black Mountain and San Marcos Peak is

under predicted on the 27th and 28th. The northern sites of Valley Center and Warner Springs

show little diurnal variation in the ozone predictions, which causes over prediction at night.

The spatial pattern of observed daily peak eight-hour averaged ozone on September 26 is

an area of ozone with little variation ranging between 40 ppb and 60 ppb in San Diego County. 

The predicted ozone shows the same pattern with concentrations between 40 ppb and 60 ppb. 

On September 27th the observed maximum eight-hour ozone is highest at Alpine and the elevated

supplemental sites. The predicted ozone shows an area of highest concentration south of Alpine. 

Peak observed eight-hour ozone on September 28 is highest inland. Predicted peak ozone has an

area of maximum concentration immediately offshore San Diego County and a second area of

maximum concentration south of Alpine. The observed maximum area in northern San Diego

County is under predicted.

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65

Figure 13a. Time series of eight-hour averaged ozone in San Diego County, September 26-29,

1997.

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66

Figure 13b. Time series of eight-hour averaged ozone in San Diego County, September 26-29,

1997.

Figure 14a. Plot of maximum predicted eight-hour averaged ozone for September 26, 1997.

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Figure 14b. Plot of maximum predicted eight-hour averaged ozone for September 27, 1997.

Figure 14c. Plot of maximum predicted eight-hour averaged ozone for September 28, 1997.

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68

4.5 Source Apportionment

The CAMx simulations for the August 4-7, 1997, and September 27-28, 1997, ozone

episodes were made using the Ozone Source Apportionment Technology (OSAT) (Environ

2005) in the CAMx model. OSAT provides information about the sources of ozone production

that lead to predicted ozone at a designated receptor. Fourteen source regions are defined in the

modeling domain. These source regions listed in Table 38 are mostly defined by the county

boundaries. Sixteen point receptors are defined which are located at the SCOS97 San Diego

County monitoring sites. These receptors are listed in Table 39.

Table 38. Source apportionment source regions.

Region CAMx ID Region CAMx ID

Ocean 1 San Luis Obispo County 2

Kern County 3 San Bernardino County 4

Santa Barbara County 5 Ventura County 6

Los Angeles County 7 Riverside County 8

Orange County 9 San Diego County 10

Imperial County 11 Mexico 12

Outer Continental Shelf 13 State of Nevada 14

Table 39. San Diego Receptors for source apportionment.

Alpine Chula Vista Del Mar El Cajon

Escondido Oceanside Otay Mesa Overland

Downtown 12th St. Black Mountain Camp Pendleton Red Mountain

San Marcos Peak Soledad Mountain Valley Center Warner Springs

The source apportionment tracks the contribution to ozone at a receptor from initial and

boundary conditions and from emissions. Ozone created from emissions is further separated into

that portion formed during VOC (volatile organic compound)-limited conditions and that portion

formed during NOx-limited conditions. The apportionment is tracked each hour of the

simulation.

Table 40 shows the results of the source apportionment for August 5. The apportionment

is listed by receptor for the hour when the peak ozone occurred at that receptor. This means that

the time of the apportionment is different for each receptor. The peak predicted ozone for the

grid cell containing the receptor is listed in the second column of Table 40. This peak value will

differ from the peak values used to calculate the model performance statistics which was a biEight-Hour Ozone Attainment Plan
69

linearly interpolated value. Column three is the contribution to the peak value from initial

conditions; column four is the contribution to the peak value from boundary conditions; columns

five and six are the contributions to the peak value from the chemical reactions. Column five

lists the contribution from ozone created during VOC-limited conditions; column six, the

contribution from ozone created during NOx-limited conditions. Columns 3-6 add up to the peak

predicted ozone. Columns seven and eight show the percentage of ozone formed from local

emissions and from transported emissions. Local emissions are from the San Diego County

source region. Transported emissions are the total from all other source regions in the modeling

domain. 

As an example, look at the Alpine receptor in Table 40. The peak ozone predicted for the

surface grid cell that includes Alpine is 98.5 ppb. Initial and boundary conditions contributed

27.2 ppb to that peak value. Emissions contributed 71.3 ppb to that peak value. So initial and

boundary conditions contribute 28% (27.2/98.5) to the peak ozone. Emissions contribute 72%

(37% + 35%) to the peak ozone. Ozone created under VOC-limited conditions is 57%

(40.9/71.3) of the emission contribution.

On August 5 initial conditions contribute 8 ppb or less to the peak ozone. Boundary

conditions contribute 21 ppb or less to the peak ozone. At the coastal sites of Oceanside and

Pendleton, the inland sites of Escondido, Valley Center, and Warner Springs, and at the elevated

sites of Red Mountain, Black Mountain, and San Marcos Peak transported emissions contribute

considerably more than local emissions to peak ozone. The slightly inland sites of San Diego

12th Street, San Diego Overland, and Chula Vista have transported emissions contributing more

than local emissions to peak ozone. Further inland at El Cajon local emissions contribute

equally with transported emissions to peak ozone. At Alpine local emissions contribute slightly

more than transported emissions to peak ozone.

Table 41 lists the ozone source apportionment for September 27. On September 27,

initial conditions contribute less than 3 ppb to the peak ozone except at Warner Springs. 

Boundary conditions contribute 29 ppb or less to the peak ozone. At the coastal sites of

Pendleton and Oceanside transported emissions contribute considerably more to peak ozone than

local emissions. At the coastal site of Del Mar transported emission contribute more to peak

ozone than local emissions. Peak ozone at the elevated sites of Red Mountain, Black Mountain,

and San Marcos Peak is contributed to more from transported emissions than local emissions. At

the inland stations of Chula Vista, San Diego 12th St., San Diego Overland. and Otay Mesa,

transported emissions contribute slightly more than local emissions to peak ozone. Further

inland at El Cajon, and Alpine local emissions contribute slightly more than transported

emissions to peak ozone.

Table 42 shows the ozone source apportionment for Alpine peak ozone for August 4 to

August 7, and September 27 and 28. Alpine is the only San Diego County site not meeting the

eight-hour ozone standard. August 4 is the only day when initial conditions contribute

significantly (32%) to peak ozone. Boundary conditions contribute little on that day. Boundary

conditions contribute approximately 21 ppb to peak ozone on the remaining days of the August

episode. Boundary conditions contribute approximately 30 ppb to peak ozone during the

Eight-Hour Ozone Attainment Plan
70

September episode. On August 4 and 7 local emissions contribute more than transported

emissions to peak ozone at Alpine. On August 5 and 6 the contributions are about equal. On

both September 27 and 28 local emissions contribute more than transported emissions to peak

ozone at Alpine. More ozone contributing to peak ozone at Alpine is formed under VOClimiting conditions than NOx-limiting conditions for all of the August and September episode

days.

Table 40. Ozone source apportionment for August 5, 1997.

Receptor Predicted

Peak Ozone

(ppb)

Initial

Conditions

(ppb)

Boundary

Conditions

(ppb)

NOx

limited

(ppb)

VOC

limited

(ppb)

Local

Emissions

Transported

Emissions

Alpine 98.5 6.3 20.9 30.4 40.9 37.5% 34.8%

Chula Vista 87.5 6.4 18.2 23.9 39.0 26.5% 45.4%

Del Mar 69.1 4.2 20.1 24.3 20.5 6.9% 58.1%

El Cajon 110.2 7.7 18.1 22.5 61.8 38.4% 38.2%

Escondido 99.7 5.6 20.3 29.8 43.9 3.9% 70.0%

Oceanside 89.3 4.5 18.3 18.1 48.4 1.7% 72.9%

Otay Mesa 99.8 7.4 19.0 23.8 49.6 31.8% 41.7%

Overland 78.8 6.3 18.7 20.9 32.9 19.8% 48.5%

12th Street 75.6 6.1 17.9 20.5 31.1 20.8% 47.4%

Black Mtn. 86.7 6.0 19.0 27.0 34.8 11.3% 60.0%

Pendleton 74.1 3.3 19.6 17.1 34.0 1.3% 67.7%

Red Mtn. 115.7 6.5 18.7 21.3 69.1 3.5% 74.7%

San Marcos Pk. 99.0 5.8 19.3 25.7 48.1 4.8% 69.8%

Soledad Mtn. 68.3 4.4 19.9 25.0 18.9 8.2% 56.2%

Valley Center 118.3 6.5 20.5 27.4 63.9 4.7% 72.5%

Warner Springs 97.2 5.4 21.2 23.2 47.5 1.2% 71.5%

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71

Table 41. Ozone source apportionment for September 27, 1997.

Receptor Predicted

Peak Ozone

(ppb)

Initial

Conditions

(ppb)

Boundary

Conditions

(ppb)

NOx

limited

(ppb)

VOC

limited

(ppb)

Local

Emissions

Transported

Emissions

Alpine 86.8 1.4 27.9 19.2 38.4 37.1% 29.1%

Chula Vista 74.9 1.8 26.5 20.4 26.3 26.7% 35.6%

Del Mar 64.5 2.1 25.1 16.0 21.3 22.2% 35.6%

El Cajon 83.2 1.6 26.6 14.3 40.6 33.7% 32.3%

Escondido 79.2 1.8 24.0 12.4 40.9 25.8% 41.6%

Oceanside 61.9 0.9 27.1 16.9 17.0 1.0% 53.8%

Otay Mesa 79.5 1.7 26.7 18.3 32.7 31.0% 33.2%

Overland 69.8 1.8 25.4 21.0 21.6 23.5% 37.5%

12th Street 67.9 1.8 24.7 19.9 21.5 23.2% 37.8%

Black Mtn. 71.8 1.9 25.1 14.7 30.1 25.0% 37.5%

Pendleton 57.9 2.4 28.9 18.6 8.0 2.2% 43.9%

Red Mtn. 68.6 0.9 27.8 19.0 20.9 4.8% 53.4%

San Marcos Pk. 74.8 1.8 24.4 14.5 34.1 23.3% 41.6%

Soledad Mtn. 66.1 2.1 25.8 18.3 19.9 21.4% 36.4%

Valley Center 70.0 1.2 26.7 21.7 20.4 15.6% 44.6%

Warner Springs 54.4 5.6 25.9 6.4 16.4 1.5% 40.6%

Table 42. Ozone source apportionment for the Alpine monitoring site for the August and

September episodes.

Alpine

Receptor

Predicted

Peak Ozone

(ppb)

Initial

Conditions

(ppb)

Boundary

Conditions

(ppb)

NOx

limited

(ppb)

VOC

limited

(ppb)

Local

Emissions

Transported

Emissions

August 4 91.0 29.4 5.9 15.2 40.6 37.7% 23.5%

August 5 98.5 6.3 20.9 30.4 40.9 37.5% 34.8%

August 6 121.6 2.9 20.4 45.2 53.2 39.0% 41.9%

August 7 105.8 0.9 21.8 33.4 49.7 53.8% 24.8%

September 27 86.8 1.4 27.9 19.2 38.4 37.1% 29.1%

September 28 81.8 0.1 33.7 6.8 41.2 36.9% 21.8%

Eight-Hour Ozone Attainment Plan
72

5.0 MODELED OZONE ATTAINMENT TEST

5.1 Procedures for Design Values and Relative Reduction Factors

The modeled attainment test for 8 hour averaged ozone (EPA 2005) is based on using the

model results in a relative sense rather than an absolute sense. The absolute sense would be

comparing the actual model predicted concentration against the standard of 80 ppb (in practice 

#84 ppb). The relative sense relies on multiplying design values from monitored data by the

relative reduction factors from model predictions. The steps to make the modeled attainment test

are:

• Calculate a site-specific current design value from monitored data.

• Calculate a site-specific relative reduction factor as the ratio of the predicted

future 8 hour average daily maximum concentration near a monitoring site to the

predicted base year 8 hour average daily maximum concentration near the same

site.

• Multiply the site-specific design value times the relative reduction factor for that

site to calculate the predicted site-specific future design value.

• If the predicted future design values is # 84 ppb, then the modeled attainment test

is passed.

The base case August 4-7, 1997, and September 27-28, 1997, ozone episodes have been

simulated with future year emissions. The base year for the site specific eight-hour ozone design

values is 2002. The future year for the modeled attainment demonstration is 2008. CAMx

simulations have been made with the 2002 and 2008 future year emissions. Relative reduction

factors (RRF) are calculated for each of the SCOS97 monitoring sites in San Diego County. 

The guidance (EPA 2005) for selecting the predicted concentration to use in calculating

the RRF recommends selecting the highest predicted value for the day from a grid cell in the

vicinity of the monitoring site. Vicinity is considered to be a grid cell with any part of its area

within 15 km of the monitoring site. For this modeling domain the daily maximum is selected

from grid cells within a 7 by 7 grid cell array with the monitoring site located within the center

grid cell of the array. The 7 by 7 array has 49 grid cells. On each side of the center grid cell are

3 grid cells of 5 km size.

The guidance recommends using the eight-hour average daily maximum of each modeled

day excluding the “ramp-up” day. For the August 4-7, 1997, ozone episode, August 3 is the

“ramp-up” day. For the September 27-28, 1997, ozone episode, September 25 and 26 are “rampup” days. The RRF for a monitoring site is the arithmetic mean of the 2008 predicted daily

maximum for all modeled days divided by the 2002 predicted average daily maximum for the

modeled days. In additions to excluding the “ramp-up” days, days with the predicted 8 hour

ozone significantly below the standard may also be excluded.

The monitored design values are calculated from the fourth highest daily maximum

eight-hour averaged ozone for the year at each monitoring site. Table 43 lists the fourth highest

Eight-Hour Ozone Attainment Plan
73

eight-hour averaged concentrations for each year from 1995 to 2005. Table 44 lists the three

year arithmetic mean of the fourth highest value for each of the three year periods from 1995 to

2005. Table 45 lists year eight-hour ozone design values which are the truncated values from

Table 44, the convention for establishing the eight-hour averaged ozone design values. For the

modeled attainment test the guidance recommends using the average of the three design values

which center on the baseline year, 2002. For a 2002 baseline year the design values for 2000-

2002, 2001-2003, and 2002-2004 are averaged. For Alpine the 2002 average design value is

(95+93+89)/3 = 92.3 ppb.

Eight-Hour Ozone Attainment Plan
74

Table 43. San Diego County eight-hour averaged ozone 4th highest concentration (ppb).

Site 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005

Alpine 107 99 93 114 92 95 96 96 89 83 87Chula Vista 78 75 81 75 70 72 71 70 54 70 70Del Mar 84 79 79 73 70 70 72 71 65 81 64El Cajon 80 90 76 86 70 77 74 73 69 71 71Escondido 83 90 83 87 70 81 76 69 77 73 69Oceanside 77 84 73 75 70 69 71 ****Otay Mesa 81 79 79 67 63 56 60 69 69 69 59Overland 75 78 74 73 73 73 83 76 74 82 6812th St 71 75 72 65 64 64 65 64 62 65 53Pendleton ** ** 83 88 76 75 76 70 81 80 68

* - Monitoring at Oceanside site ended in March, 2002.** - Monitoring at Camp Pendleton site began in April, 1997 (replacement site for Oceanside).Table 44. San Diego County three year average of the 4th highest eight-hour ozone (ppb).

Site 1995-1997 1996-1998 1997-1999 1998-2000 1999-2001 2000-2002 2001-2003 2

Alpine 99.7 102.0 99.7 100.3 94.3 95.7 93.7 

Chula Vista 78.0 77.0 75.3 72.3 71.0 71.0 65.0 Del Mar 80.7 77.0 74.0 71.0 70.7 71.0 69.3 El Cajon 82.0 84.0 77.3 77.7 73.7 74.7 72.0 Escondido 85.3 86.7 80.0 79.3 75.7 75.3 74.0 

Oceanside 78.0 77.3 72.7 71.3 70.0 70.0 71.0 Otay Mesa 79.7 75.0 69.7 62.0 59.7 61.7 66.0 Overland 75.7 75.0 73.3 73.0 76.3 77.3 77.7 12th St 72.7 70.7 67.0 64.3 64.3 64.3 63.7 Pendleton ** ** 82.3 79.7 75.7 73.7 75.7 

* - Monitoring at Oceanside site ended in March, 2002.** - Monitoring at Camp Pendleton site began in April, 1997 (replacement site for Oceanside).Eight-Hour Ozone Attainment Plan
75

Table 45. San Diego County eight-hour ozone design values (ppb).

Site 1995-1997 1996-1998 1997-1999 1998-2000 1999-2001 2000-2002 2001-2003 2

Alpine 99 102 99 100 94 95 93 

Chula Vista 78 77 75 72 71 71 65 Del Mar 80 77 74 71 70 71 69 El Cajon 82 84 77 77 73 74 72 Escondido 85 86 80 79 75 75 74 

Oceanside 78 77 72 71 70 70 71 Otay Mesa 79 75 69 62 59 61 66 Overland 75 75 73 73 76 77 77 12th St 72 70 67 64 64 64 63 Pendleton ** ** 82 79 75 73 75 

* - Monitoring at Oceanside site ended in March, 2002.** - Monitoring at Camp Pendleton site began in April, 1997 (replacement site for Oceanside).Eight-Hour Ozone Attainment Plan
76

5.2 Eight-Hour Ozone Standard Attainment Demonstration Test

Table 46 lists the 2002 and 2008 daily maximum predicted eight-hour ozone for August

4, 5, 6, 7 and September 27 and 28. These concentrations are averaged to calculate the mean

average eight-hour maximum for 2002 and 2008 shown in Table 47. The 2008 mean is divided

by the 2002 mean to calculate the relative reduction factor (RRF) shown in the table. The RRF

for Alpine is 0.940. This value is multiplied by the average design value at Alpine (92.3 ppb) to

estimate the 2008 future year design value of 86 ppb. Since this value exceeds 84 ppb the

modeled attainment demonstration test is not passed. However, since 86 ppb is close to 84 ppb,

then “weight-of-evidence” analyses should be considered as part of an attainment demonstration.

Table 46. Daily maximum predicted eight-hour ozone near a monitoring site (ppb).

Predicted Peak Ozone Predicted Peak

Ozone

2002 2008

Site 4-Aug 5-Aug 6-Aug 7-Aug 27-Sep 28-Sep 4-Aug 5-Aug 6-Aug 7-Aug 27-Sep28-Sep

ALPN 75.1 92.5 106.7 91.8 72.8 73.7 71.4 87.1 100.4 86.2 68.1 68.3

CHVT 67.5 90.6 85.8 69.7 68.8 72.2 65.3 85.8 82.6 67.3 65.8 67.3

DMMC 61.8 83.1 67.0 67.6 63.7 76.3 59.6 78.4 64.6 65.0 61.1 72.6

ECAJ 75.1 92.5 103.9 88.3 72.4 73.7 71.4 87.1 98.2 83.7 68.1 68.3

ESCO 77.4 94.5 90.3 85.8 70.5 62.6 73.7 88.3 85.8 81.3 66.5 59.7

OCEA 67.3 86.5 64.5 67.1 63.5 73.3 64.0 81.0 62.6 64.9 61.0 70.4

OTAY 73.7 92.5 89.3 81.0 72.4 73.7 70.2 87.1 86.8 77.3 68.1 68.3

SDOV 66.7 86.1 84.8 73.3 68.7 74.7 64.0 80.7 81.3 69.8 64.9 69.1

SD12 57.5 78.7 72.6 55.9 64.8 77.0 56.0 74.4 70.3 54.7 62.3 73.1

BLKM 75.6 94.4 84.8 79.6 69.8 71.0 71.9 88.3 81.3 75.7 66.2 66.6

PEND 69.9 88.3 64.5 67.1 65.5 73.3 66.4 82.7 62.6 64.9 62.9 70.4

REDM 76.6 94.7 79.0 85.6 65.0 64.4 71.4 88.0 76.0 80.0 62.4 61.7

SMPK 75.6 95.8 87.7 82.9 69.8 64.1 71.9 88.6 83.6 79.1 66.2 60.2

SOLM 55.2 77.9 61.2 58.1 62.0 77.9 53.3 73.3 59.9 56.7 59.4 74.0

VCEN 77.7 95.8 91.4 85.8 70.5 60.6 73.7 88.6 86.3 81.3 66.5 58.3

WSPR 75.9 93.2 91.0 89.7 62.8 50.7 71.3 86.1 86.2 82.8 59.5 49.6

Eight-Hour Ozone Attainment Plan
77

Table 47. Future year eight-hour ozone design values.

Site 2002 Mean

Predicted

Concentration

(ppb)

2008 Mean

Predicted

Concentration

(ppb)

RRF 2002 Average

Design Value

(ppb)

2008 Future

Year

 Design Value

(ppb)

ALPN 85.4 80.3 0.940 92.3 86

CHVT 75.8 72.4 0.955 66.7 63

DMMC 69.9 66.9 0.957 70.7 67

ECAJ 84.3 79.5 0.943 72.3 68

ESCO 80.2 75.9 0.946 74.0 70

OCEA 70.4 67.3 0.956 70.5 67

OTAY 80.4 76.3 0.949 65.3 61

SDOV 75.7 71.6 0.946 77.0 72

SD12 67.8 65.1 0.960 63.3 60

BLKM* 79.2 75.0 0.947

PEND 71.4 68.3 0.957 75.0 71

REDM* 77.6 73.3 0.945

SMPK* 79.3 74.9 0.945

SOLM* 65.4 62.8 0.960

VCEN* 80.3 75.8 0.944

WSPR* 77.2 72.6 0.940

*Not an official ozone monitoring site for San Diego County.

Eight-Hour Ozone Attainment Plan
78

6.0 REFERENCES

ARB, 1989: Proposed Identification of Districts Affected by Transported Air Pollutants which

Contribute to Violations of the State Ambient Air Quality Standards for Ozone. Staff Report,

Meteorology Section, Technical Support Division, California Air Resources Board, October

1989.

ARB, 1993: Assessment and Mitigation of the Impacts of Transported Pollutants on Ozone

Concentrations in California. Staff Report, Technical Support Division, California Air

Resources Board, June 1993.

ARB, 1996: Second Triennial Review of the Assessment of the Impacts of Transported

Pollutants on Ozone Concentrations in California (Revised). Staff Report, Technical

Support Division, California Air Resources Board, November 1996.

ARB, 2000: Modeling Protocol for Regional 1-Hour and 8-Hour Ozone Modeling in Southern

California for the 2003 State Implementation Plans (Draft #3). Control Strategy Modeling

Section, California Air Resource Board, September 18, 2000, Sacramento, CA, 46pp.

Boucouvala, D., R. Bornstein, J. Wilkenson, D. Miller, 2003: MM5 Simulations of a NARSTOSCOS97 Episode, Atmospheric Environment, Supplement No. 2, S95-S117.

Boucouvala, D., and R. Bornstein, 2003: Analysis of transport patterns during a SCOS97-

NARSTO episode, Atmospheric Environment, Supplement No. 2, S73-S94.

Croes, B.E, E.M. Fujita, 2003: Overview of the 1997 Southern California Study (SCOS97-

NARSTO), Atmospheric Environment, Supplement No. 2, S3-S26.

Emery, C., E. Tai, and G. Yarwood, 2001: Enhanced Meteorological Modeling and Performance

Evaluation for Two Texas Ozone Episodes. Environ International Corporation, Novato, CA,

August 31, 2001, 235pp.

ENVIRON, 2005. “USER’S GUIDE, CAMx, Comprehensive Air Quality Model with

Extensions, Version 4.20. June 2005. ENVIRON International Corporation, Novato,

California, 236p.

EPA, 2005: Guidance on the Use of Models and Other Analyses in the Attainment

Demonstration for the 8-hour Ozone NAAQS. U.S. Environmental Protection Agency, EPA454/R-05-002, October 2005

Hayes, T.P., J.J.R. Kinney, and N.J.M. Wheeler, 1984: California Surface Wind Climatology.

Staff Report, Aerometric Data Division, California Air Resources Board.

Eight-Hour Ozone Attainment Plan
79

Rosenthal, J. S., R. A. Helvey, T. E. Bettalino, C. Fisk, and P. W. Greiman, 2003:Ozone

transport by mesoscale and diurnal wind circulations across southern California,

Atmospheric Environment, Supplement No. 2, S51-S71.

Scire, J. S., F. R. Robe, F. E. Fernau, and R. J. Yarmartino: A User’s Guide for the CALMET

Meteorological Model (Version 5). Earth Tech Inc., January 2000, 332pp.

SDAPCD, 2002: Modeling Protocol for Regional 1-Hour and 8-Hour Ozone Modeling in

Southern California for the 2003 State Implementation Plans, San Diego County Modeling

Supplement. Modeling & Meteorology Section, San Diego Air Pollution Control District,

December 2, 2002, San Diego, CA, 14pp.

Seaman, N.L., D.R. Stauffer, and A.M. Lario. 1995. A Multi-Scale Four Dimensional Data

Assimilation System Applied in the San Joaquin Valley During SARMAP. Part 1: Modeling

Design and Basic Performance Characteristics. Journal of Applied Meteorology, 34:1739-

1776.

Wagner, Kit K., Judith Lake, and Bill Brick, 2005. Application of CAMx to a San Diego County

Attainment Demonstration. Paper 1079, Proceedings of the Air & Waste Management

Association’s (AWMA) 98th Annual Conference & Exhibition, June 21-24, 2005,

Minneapolis, Minnesota.

Wheeler, N.J.M., 2003: Quality Assurance, Review, and Optimization of Meteorological

Modeling for the 1997 Southern California Ozone Study (Prepared for: The San Diego Air

Pollution Control District). Final Report STI-902220-2490-FR, Sonoma Technology Inc.,

August 29, 2003, Petaluma, CA, 121pp.

Eight-Hour Ozone Attainment Plan
Modeling Protocols for a 2007 Modeling Attainment

Demonstration for San Diego County

Eight-Hour Ozone Attainment Plan
MODELING PROTOCOL FOR REGIONAL 1-HOUR AND

8-HOUR OZONE MODELING IN SOUTHERN CALIFORNIA

FOR THE 2003 STATE IMPLEMENTATION PLANS

SAN DIEGO COUNTY MODELING SUPPLEMENT

December 2, 2002

Prepared for:

Southern California Modeling Stakeholders

Prepared by:

Modeling & Meteorology Section

Technical Services Division

San Diego Air Pollution Control District

9150 Chesapeake Drive

San Diego, CA 92123

Eight-Hour Ozone Attainment Plan
SCOS Regional Modeling Protocol Document San Diego County Modeling Supplement 12/2/2002 i

CONTRIBUTORS

Kit Wagner

Bill Brick

Judy Lake

Carl Selnick

Eight-Hour Ozone Attainment Plan
SCOS Regional Modeling Protocol Document San Diego County Modeling Supplement 12/2/2002 ii

TABLE OF CONTENTS

INTRODUCTION

Background and Objectives ....................................................................... 1

MODELING DOMAIN .................................................................................... 2

EPISODE SELECTION .................................................................................... 2

AIR QUALITY MODEL SELECTION ............................................................. 5

HORIZONTAL AND VERTICAL GRID RESOLUTION

Horizontal Grid Resolution ....................................................................... 5

• Air Quality Modeling .................................................................... 5

• Meteorological Modeling .............................................................. 5

• Emission Inventory ...................................................................... 5

Vertical Resolution ................................................................................... 5

• Air Quality Modeling .................................................................... 5

• Meteorological Modeling .............................................................. 6

METEOROLOGICAL INPUTS ....................................................................... 7

Proposed Approaches ............................................................................... 7

Meteorological Input Validation and Technical Review .............................. 7

EMISSION INVENTORY ................................................................................ 7

Anthropogenic Emissions ......................................................................... 7

• Point Sources .............................................................................. 7

• Area Sources ............................................................................... 7

• On-Road Mobile Sources ............................................................. 7

• Other Mobile Sources .................................................................. 7

• Day-Specific Emissions ................................................................ 7

Natural Emissions .................................................................................... 7

• Biogenics .................................................................................... 7

• Soil Nox Emissions ...................................................................... 7

• Oil and Gas Seeps ....................................................................... 7

Organic Gas Speciation ........................................................................... 7

Gridding Surrogates ................................................................................. 7

Northern Mexico Inventory ....................................................................... 8

Quality Assurance Procedures .................................................................. 8

Eight-Hour Ozone Attainment Plan
SCOS Regional Modeling Protocol Document San Diego County Modeling Supplement 12/2/2002 iii

Emission Projections ................................................................................ 8

INITIAL AND BOUNDARY CONDITIONS .................................................... 8

Initial Conditions ..................................................................................... 8

Boundary Concentrations ......................................................................... 8

MODEL PERFORMANCE EVALUATION ..................................................... 8

Statistical and Graphical Analyses ............................................................ 8

Multi-Species Evaluations ...................................................................... 11

Aloft Comparisons .................................................................................. 11

Diagnostic Simulations .......................................................................... 11

USE OF THE MODEL RESULTS .................................................................. 11

Carrying Capacity Estimation ................................................................ 11

Attainment Demonstration ...................................................................... 11

Transport Assessment ............................................................................. 11

TECHNICAL OVERSIGHT ........................................................................... 12

SCHEDULE AND DELIVERABLES .............................................................. 13

Schedule ................................................................................................ 13

Deliverables .......................................................................................... 13

REFERENCES ............................................................................................... 14

Eight-Hour Ozone Attainment Plan
SCOS Regional Modeling Protocol Document San Diego County Modeling Supplement 12/2/2002 1

INTRODUCTION

Background and Objectives

This document is a supplement to the modeling protocol, “Modeling Protocol For

Regional 1-Hour And 8-Hour Ozone Modeling In Southern California For The 2003 State

Implementation Plans (Draft #3)” dated September 18, 2000, (the Protocol) prepared by the

California Air Resources Board (ARB) Staff. This supplement describes the modifications and

additions to the modeling protocol for photochemical modeling of ozone for San Diego County.

In 2001, San Diego County attained the one-hour average National Ambient Air Quality

Standard for ozone. The San Diego Air Pollution Control District (SDAPCD) is submitting a

request for redesignation as attainment of this National one-hour ozone standard. In 2002, San

Diego County remains non-attainment of the California one-hour average ozone standard and

will likely be designated as non-attainment of the National eight-hour average ozone standard

when those designations occur. San Diego County is also impacted by transport of ozone and

ozone precursors from the South Coast Air Basin and from Mexico.

Photochemical modeling of ozone is needed to demonstrate that current and future

emission control measures provide for attainment of the California one-hour ozone standard and

the National eight-hour ozone standard in San Diego County. In the event that San Diego

County becomes non-attainment of the National one-hour ozone standard, modeling will be used

to demonstrate when attainment will be restored. Modeling will be used to assess the

effectiveness of local emission control measures. Modeling will be used to evaluate the role of

transport on ozone in San Diego County and the benefits of upwind emission reductions on

ozone in San Diego County. The San Diego Air Pollution Control District will carry out the

photochemical modeling for San Diego County in conjunction with modeling efforts of the

California Air Resources Board and the South Coast Air Quality Management District

(SCAQMD).

This supplement should be used in combination with the Protocol to understand the

modeling procedures to be followed. Procedures not modified or appended in this document will

be implemented as described in the Protocol. As with the Protocol this supplement will be

updated as circumstances warrant.

Eight-Hour Ozone Attainment Plan
SCOS Regional Modeling Protocol Document San Diego County Modeling Supplement 12/2/2002 2

MODELING DOMAIN

The modeling domain will be as described in the Protocol. Both Universal Transverse

Mercator (UTM) coordinates and Lambert Conformal coordinates are used in the modeling. 

There will be some slight differences in domains for the different coordinate systems. The

domain in UTM coordinates is defined by the UTM zone and the easting and northing

coordinates. This domain is

UTM Zone 11, 150000m to700000m Easting, 3580000m to 3950000m Northing.

The domain in Lambert Conformal coordinates is defined by the latitudes where the conic

projection intersects the sphere (standard parallels), the longitude of the center of the map

(central meridian), the latitude of the projection origin, and the boundaries of the domain. The

central meridian and latitude of origin define the center or origin of the projection. The

boundaries of the domain are measured from this origin. This domain is

Standard parallels 30 degrees north 60 degrees north

Central meridian -118 degrees (west)

Latitude of origin 30 degrees north

Extent -290000m to +290000m east coordinate

 225000m to 625000m north coordinate.

EPISODE SELECTION

There are four SCOS97 ozone episodes that are of interest for modeling in San Diego

County. Those episodes in priority order are:

1. August 3-7, 1997

2. September 26-29, 1997

3. October 30 - November 1, 1997

4. September 3-6, 1997

Table 1 on the following page lists the SCOS97 ozone episodes, episode types, and maximum

one-hour and eight-hour ozone for the sub-regions.

August 3-7, 1997, is an ozone episode where both local contributions and transport

contributed to exceedances of the standards in San Diego County. Peak one-hour ozone during

this episode was 0.12 ppm on August 3 at Alpine and on August 5 at Otay Mesa. Exceedances

of the California one-hour standard were wide spread on August 5. Alpine alone exceeded the

California one-hour standard on August 6. The peak eight-hour averaged ozone in San Diego

County during this episode was 0.099 ppm which occurred at a supplemental monitor. The

highest eight-hour averaged ozone at an official monitor was 0.087 at Alpine on August 5.

September 26-29, 1997, is weekend episode. Peak ozone in San Diego County occurred

on Sunday, September 28, with a concentration of 0.11 ppm at Alpine. Additional exceedances

Eight-Hour Ozone Attainment Plan
SCOS Regional Modeling Protocol Document San Diego County Modeling Supplement 12/2/2002 3

of the California one-hour standard occurred at other monitors in the County. Both local sources

and transport contributed to the exceedances. Exceedances of the ozone standard on weekends

are important in San Diego County. In 1997 forty-two percent of the days with exceedances of

the California one-hour ozone standard were on Saturday or Sunday. In 2001 this had increased

to fifty-two percent. In San Diego County during this episode 0.096 ppm was the peak eighthour averaged ozone which occurred at a supplemental monitor. Eight-hour averaged ozone did

not exceed 0.084 ppm at the official monitors during this episode.

October 30 to November 1, 1997, is an episode with off-shore transport of ozone and

ozone precursors from Los Angeles to San Diego County. Peak one-hour ozone was 0.14 ppm

on October 31, at San Marcos Peak, a supplemental monitor. Peak one-hour ozone at the official

monitors was 0.12 ppm on October 31, at several sites and at Chula Vista on November 1. 

Exceedances of the California one-hour standard occurred at several monitors on October 30-31,

and November 1. Although transport was overwhelming at many monitors, several monitors had

local contributions to ozone standard exceedances. Eight-hour averaged ozone peaked at 0.119

ppm at a supplemental monitor. Peak eight-hour averaged ozone at official monitors was 0.099

at Chula Vista on November 1. Eight-hour averaged ozone exceeded 0.084 ppm at Camp

Pendelton on October 30, and at Del Mar, Chula Vista, and Camp Pendelton on October 31.

September 3-6, 1997 is an episode with transport aloft that caused an ozone

concentration of 0.13 ppm at a supplemental monitor at Black Mountain on September 4. 

Although, the 0.13 ppm at Black Mountain exceeded the ozone standards in San Diego County

during the this episode, there were no exceedances of the State or National one-hour standards at

the official monitors. For this reason this episode is not as well suited for emission control

strategy development as the other episodes. The eight-hour averaged peak ozone was 0.090 ppm

at a supplemental monitor. Eight-hour averaged ozone did not exceed 0.084 ppm at the official

monitors during this episode.

Eight-Hour Ozone Attainment Plan
SCOS Regional Modeling Protocol Document San Diego County Modeling Supplement 12/2/2002 4

Table 1. Characteristics of SCOS97 Episodes

Episode Days of Week Episode

Type(s)

Maximum 1-Hour/8-Hour Ozone Concentration (pphm)

SCAB Ventura San Diego Mojave

Desert

Santa

Barbara

Imperial

County

Northern Mexico

Mexicali Tijuana/

Rosarito

August 3-7, 1997 Sunday–Thursday 1-, 2-, 3- 19 / 13.0 13 / 11.5 12 / 9.9 14 / 11.3 10 / 8.7 10 / 9.3 9 / 7.5 10 / 8.0

September 3-6, 1997 Wednesday–Saturday 1-, 2, 3- 16 / 9.9 10 / 7.5 13 / 9.0 10 / 7.7 9 / 7.5 8 / 5.8 10 / 6.6 8 / 6.4

September 26-29, 1997 Friday–Monday 1-, 2-, 4- 17 / 10.7 12 / 9.7 11 / 9.6 10 / 7.7 11 / 9.3 11 / 7.0 13 / 9.8 11 / 8.5

October 30–November 1, 1997 Thursday–Saturday 5 10 / 6.3 11 / 8.1 14 / 11.9 8 / 7.2 9 / 7.6 12 / 8.3 21 / 11.4 12 / 9.6

National 1- and 8-Hour Design Values: 1997‡

1998‡

1999‡

21.5 / 14.8

21.7 / 15.4

21.1 / 14.7

15.2 / 11.5

14.4 / 11.2

13.4 / 10.6

13.8 / 9.9

13.5 / 10.2

13.5 / 9.9

17.5 / 12.4

16.7 / 12.7

16.6 / 11.8

13.0 / 8.9

13.0 / 8.7

10.8 / 8.2

16.0 / 10.3

14.0 / 9.3

13.9 / 9.1

State 1-Hour Design Value: 1997‡

1998‡

1999‡

24

22

21

15

14

14

13

13

13

16

18

16

11

11

10

16

18

14

Episode Types

1 South Coast Air Basin ozone maximum

2 upper level transport to San Diego

3 secondary South Coast Air Basin ozone maximum with transport into Mojave Desert

4 eddy transport to Ventura following episode in South Coast Air Basin

5 off-shore surface transport to San Diego

Eight-Hour Ozone Attainment Plan
SCOS Regional Modeling Protocol Document San Diego County Modeling Supplement 12/2/2002 5

AIR QUALITY MODEL SELECTION

The Comprehensive Air Quality Model with Extension (CAMx) will be used for

photochemical ozone modeling in San Diego County. Version 3.10 (ENVIRON, 2002) with the

Carbon Bond IV chemical mechanism will be used. Alternate air quality models will be

considered if modeling work by the ARB and SCAQMD demonstrate that another model may be

more appropriate for southern California.

HORIZONTAL AND VERTICAL GRID RESOLUTION

Horizontal Grid Resolution

• Air Quality Modeling

The CAMx modeling will use a 5km horizontal grid resolution. Depending on the

meteorological model used to prepare the meteorological inputs the domain will be in either the

UTM coordinate system or the Lambert Conformal coordinate system. This grid resolution

creates a 116 east-west by 80 north-south grid system within both coordinate systems.

• Meteorological Modeling

The meteorological modeling with MM5 also will use a 5km horizontal grid resolution in

Lambert Conformal coordinates for the fine-scale domain. The fine-scale domain is coincident

with the air quality modeling domain. Meteorological modeling with the CALMET

meteorological model will use a 5km horizontal grid resolution in UTM coordinates.

• Emission Inventory

The 2km horizontal grid resolution emission inventory in UTM coordinates will be

mapped into the 5km Lambert Conformal air quality model grid coordinates.

Vertical Resolution

• Air Quality Modeling

The air quality model will have sixteen (16) layers from the earth’s surface to

approximately 5000 m AGL. The specific vertical resolution depends upon the method used to

create the meteorological inputs. If the meteorological inputs are created with a diagnostic

model such as CALMET, the vertical resolution of CAMx will be the CALMET vertical

resolution. When MM5 is used to create the meteorological inputs, the vertical resolution of

CAMx will be the MM5 vertical resolution for the lower sixteen layers.

Eight-Hour Ozone Attainment Plan
SCOS Regional Modeling Protocol Document San Diego County Modeling Supplement 12/2/2002 6

• Meteorological Modeling

The vertical resolution of the meteorological modeling for CALMET and MM5 for the

sixteen layers are shown in Table 2.

Table 2. Vertical Domain for the Meteorological Modeling

Layer No. CALMET layers+ (meters) MM5 layers* (meters)

1 20 58

2 60 146

3 100 250

4 200 369

5 300 490

6 400 613

7 600 737

8 800 879

9 1000 1023

10 1500 1234

11 2000 1451

12 2500 1767

13 3000 2095

14 3500 2942

15 4000 3962

16 5000 4986

+

 Heights are for a constant height terrain following coordinate system.

*

 The vertical coordinate system for MM5 is based on a normalized pressure scales. The layer

heights are approximate based on a standard atmosphere and are height above the terrain.

Eight-Hour Ozone Attainment Plan
SCOS Regional Modeling Protocol Document San Diego County Modeling Supplement 12/2/2002 7

METEOROLOGICAL INPUTS

Proposed Approaches

The SDAPCD will sponsor an independent review of the CALMET and MM5

meteorological modeling efforts for the SCOS97 ozone episodes which are described in the

Protocol. The review will evaluate the meteorological inputs that have been prepared by the

ARB and SCAQMD for the SCOS97 domain as to their suitability for photochemical modeling

of ozone in San Diego County. This study will make recommendations for any modifications or

enhancements that may be required to address the specific concerns for modeling of San Diego

County.

Meteorological Input Validation and Technical Review

Meteorological input validation and technical review will be carried out as described in

the Protocol with specific emphasis on the region of San Diego County.

EMISSION INVENTORY

The 1997 base year emission inventory photochemical modeling inputs will be prepared

as described in the Protocol and created by the ARB staff. Refer to the Protocol for a discussion

of the following emission inventory topics and procedures.

Anthropogenic Emissions

• Point Sources

• Area Sources

• On-Road Mobile Sources

• Other Mobile Sources

• Day-Specific Emissions

Natural Emissions

• Biogenics

• Soil NOx Emissions

• Oil and Gas Seeps

Organic Gas Speciation

Gridding Surrogates

Eight-Hour Ozone Attainment Plan
SCOS Regional Modeling Protocol Document San Diego County Modeling Supplement 12/2/2002 8

Northern Mexico Inventory

Quality Assurance Procedures

Emission Projections

The future year emissions will be projected as described in the Protocol. 

INITIAL AND BOUNDARY CONDITIONS

Initial and boundary conditions for the photochemical ozone modeling will be prepared

as described in the Protocol.

Initial Conditions

Boundary Concentrations

MODEL PERFORMANCE EVALUATION

The model performance evaluation will be carried out as described in the Protocol.

Statistical and Graphical Analyses

• Subregional Performance

Emphasis on subregional performance will be placed on model performance within San

Diego County. The four subregions of the South Coast Air Basin listed in the Protocol will not

be evaluated separately.

Supplemental air quality monitors were sited in San Diego County during SCOS97. 

Official monitoring sites along with the supplemental monitors are listed in Table 3. The

locations of the monitors are shown in Figure 1. Several of the supplemental monitors were

sited atop mountains. These sites are Black Mountain (BLKM), Red Mountain (REDM), San

Marcos Peak (SMPK), and Mount Soledad (SOLM). These sites are not representative of the

surrounding surface air quality. Their purpose for SCOS97 was to observe aloft transport. The

air quality model scientific formulation with the 5 km grid resolution is not designed to resolve

the large changes in terrain elevation over the small horizontal distances occurring at these sites. 

These sites will not be included in the statistical model performance evaluation.

Eight-Hour Ozone Attainment Plan
SCOS Regional Modeling Protocol Document San Diego County Modeling Supplement 12/2/2002 9

Table 3. San Diego County air quality monitoring sites during SCOS97

Site Identifer Elevation

MSL meters

Pollutants

Sampled

Alpine ALPN 603 O3

Camp Pendelton PEND 6 O3, NO, NO2, NOX

Chula Vista CHVT 56 O3, NO, NO2, NOX, CO, SO2

Del Mar DMMC 35 O3

El Cajon ECAJ 143 O3, NO, NO2, NOX, CO, THC, CH4, NMHC

Escondido ESCO 204 O3, NO, NO2, NOX, CO

Oceanside OCEA 37 O3, NO, NO2, NOX, CO

Otay Mesa OTAY 155 O3, NO, NO2, NOX, CO, SO2

San Diego Overland SDOV 135 O3, NO, NO2, NOX, CO

San Diego 12th

Street

SD12 6 O3, NO, NO2, NOX, CO, SO2, THC, CH4,

NMHC

Supplemental Monitors

Black Mountain BLKM 473 O3

Mount Soledad SOLM 251 O3, NO, NO2, NOX, NOY

Red Mountain REDN 552 O3

San Marcos Peak SMPK 549 O3

Valley Center VCEN 414 O3

Warner Springs WSPR 945 O3

Eight-Hour Ozone Attainment Plan
SCOS Regional Modeling Protocol Document San Diego County Modeling Supplement 12/2/2002 10

Figure 1 Air quality monitoring sites in San Diego County during SCOS97.

Eight-Hour Ozone Attainment Plan
SCOS Regional Modeling Protocol Document San Diego County Modeling Supplement 12/2/2002 11

Multi-Species Evaluations

Ozone precursors and secondary species were not measured as extensively in San Diego

County as they were in the South Coast Air Basin during SCOS97. To the extent that

measurements are available, model performance for these species will be assessed with emphasis

on San Diego County.

Aloft Comparisons

Qualitative comparisons will be made between model predictions and air quality

measurements made aloft in San Diego County. This includes aircraft and ozone sonde

measurements along with the mountain top supplemental sites in San Diego County, BLKM,

REDM, SMPK, and SOLM.

Diagnostic Simulations

The diagnostic simulations proposed in the Protocol will made. The analysis of these

diagnostic simulations will focus on impacts in San Diego County.

USE OF THE MODELING RESULTS

Carrying Capacity Estimation

An estimate of carrying capacity for San Diego County will be prepared if required by

the ARB or U.S. EPA. The estimate will be made using the procedures in the Protocol.

Attainment Demonstration

Demonstrations of attainment of the ozone standards in San Diego County will be carried

out as describe in the Protocol using relative reduction factors. Attainment will be demonstrated

for the State one-hour and the National proposed eight-hour ozone standards. The specific years

for future year simulations and attainment demonstrations will be chosen based on future

guidance from the U.S. EPA and ARB.

If San Diego County fails to maintain attainment of the National one-hour ozone

standard, modeling simulations will be used to demonstrate when attainment will be restored.

Transport Assessment

Transport of ozone and ozone precursors into San Diego County will be evaluated using

the modeling simulations. Trajectory analysis using the meteorological inputs will be used to

identify specific source-receptor relationships both at the surface and aloft. The photochemical

ozone modeling simulations will be used to quantify the estimates of transport impacts.

Eight-Hour Ozone Attainment Plan
SCOS Regional Modeling Protocol Document San Diego County Modeling Supplement 12/2/2002 12

One approach for transport assessment will use subregional modifications to the emission

inventory model inputs. Anthropogenic emissions in the South Coast Air Basin, for example,

will be set to zero for a simulation of a SCOS97 episode. The difference in model predictions

between the base case and this sensitivity simulation will be analyzed to determine the impact of

transport on ozone in San Diego County. 

A second approach for transport assessment will use the Ozone Source Apportionment

Technology (OSAT) capabilities within CAMx. Procedures will be created to use OSAT to

estimate the relative contributions of transport and local emission sources to exceedances of the

ozone standards. OSAT will also be used to examine the importance of low level over-water

transport and transport aloft of ozone and ozone precursors to ozone measured in San Diego

County.

TECHNICAL OVERSIGHT

This modeling project will seek review from the Southern California modeling

stakeholders and the SCOS97 technical working groups.

Eight-Hour Ozone Attainment Plan
SCOS Regional Modeling Protocol Document San Diego County Modeling Supplement 12/2/2002 13

SCHEDULE AND DELIVERABLES

Schedule

A preliminary schedule for photochemical ozone modeling for San Diego County is

shown in Table 4.

Table 4. Schedule for San Diego County Photochemical Modeling

Activity Begin Date End Date

Prepare base case model inputs October 2002 March 2003

Base case simulations and model performance evaluation November 2002 May 2003

Diagnostic and sensitivity simulations November 2002 July 2003

Source apportionment simulations January 2003 July 2003

Future year and attainment demonstration simulations March 2003 October 2003

Deliverables

San Diego County will provide interim summaries and graphics of the photochemical

modeling to the stakeholders and technical working groups for review and comments. At the

completion of the project the attainment demonstration and transport assessment along with

documentation and electronic files will be made available.

Eight-Hour Ozone Attainment Plan
SCOS Regional Modeling Protocol Document San Diego County Modeling Supplement 12/2/2002 14

REFERENCES

ENVIRON, 2002. “USER’S GUIDE, Comprehensive Air Quality Model with Extensions,

Version 3.10. April 2002. ENVIRON International Corporation, Novato, California.

Eight-Hour Ozone Attainment Plan
MODELING PROTOCOL FOR REGIONAL 1-HOUR AND

8-HOUR OZONE MODELING IN SOUTHERN CALIFORNIA

FOR THE 2003 STATE IMPLEMENTATION PLANS

(DRAFT #3)

September 18, 2000

Prepared for:

Southern California Modeling Stakeholders

Prepared by:

Control Strategy Modeling Section

Modeling & Meteorology Branch

Planning & Technical Support Division

California Air Resources Board

P.O. Box 2815

Sacramento, CA 95812

Eight-Hour Ozone Attainment Plan
SCOS Regional Modeling Protocol Document (DRAFT #3, 09/18/00) 2

CONTRIBUTORS

Paul Allen

John DaMassa

Bruce Jackson

Don McNerny

Elliot Mulberg

Mena Shah

Southern California Stakeholders

Eight-Hour Ozone Attainment Plan
SCOS Regional Modeling Protocol Document (DRAFT #3, 09/18/00) i

TABLE OF CONTENTS

INTRODUCTION

Background and Objectives.............................................................................1

MODELING DOMAIN...........................................................................................3

EPISODE SELECTION..........................................................................................5

AIR QUALITY MODEL SELECTION................................................................8

HORIZONTAL AND VERTICAL GRID RESOLUTION

Horizontal Grid Resolution ...........................................................................11

• Air Quality Modeling ......................................................................11

• Meteorological Modeling................................................................11

• Emission Inventory..........................................................................12

Vertical Resolution ........................................................................................12

• Air Quality Modeling ......................................................................12

• Meteorological Modeling................................................................13

METEOROLOGICAL INPUTS..........................................................................15

Previous Applications....................................................................................16

Proposed Approaches....................................................................................16

• Diagnostic Modeling .......................................................................16

• Prognostic Modeling .......................................................................17

• Hybrid Approach.............................................................................17

Meteorological Input Validation and Technical Review...............................17

EMISSION INVENTORY....................................................................................22

Anthropogenic Emissions..............................................................................22

• Point Sources...................................................................................22

• Area Sources....................................................................................23

• On-Road Mobile Sources ................................................................23

• Other Mobile Sources......................................................................24

• Day-Specific Emissions ..................................................................24

Natural Emissions..........................................................................................25

• Biogenics .........................................................................................25

• Soil Nox Emissions .........................................................................27

• Oil and Gas Seeps............................................................................27

Organic Gas Speciation.................................................................................27

Gridding Surrogates ......................................................................................27

Eight-Hour Ozone Attainment Plan
SCOS Regional Modeling Protocol Document (DRAFT #3, 09/18/00) ii

Northern Mexico Inventory ...........................................................................28

Quality Assurance Procedures......................................................................28

Emission Projections.....................................................................................28

INITIAL AND BOUNDARY CONDITIONS

Initial Conditions...........................................................................................30

Boundary Concentrations..............................................................................30

MODEL PERFORMANCE EVALUATION......................................................32

Statistical and Graphical Analyses ...............................................................32

Multi-Species Evaluations.............................................................................33

Aloft Comparisons.........................................................................................33

Diagnostic Simulations..................................................................................34

USE OF THE MODEL RESULTS ......................................................................36

Carrying Capacity Estimation.......................................................................36

Attainment Demonstration.............................................................................37

Transport Assessment....................................................................................38

TECHNICAL OVERSIGHT................................................................................39

SCHEDULE AND DELIVERABLES

Schedule.........................................................................................................40

Deliverables...................................................................................................40

REFERENCES.......................................................................................................42

Eight-Hour Ozone Attainment Plan
SCOS Regional Modeling Protocol Document (DRAFT #3, 09/18/00) iii

ACRONYMS

Several acronyms are used in the modeling protocol document. For convenience,

the acronyms used are listed here to aid the reader.

AGL – Above Ground Level

AQMP – Air Quality Management Plan

ARB – Air Resources Board

AUSPEX – Atmospheric Utility Signatures, Predictions, and EXperiments

AVHRR – Advanced Very High Resolution Radiometer

CAMx – Comprehensive Air-Quality Model with Extensions

CBM – Carbon Bond Mechanism

CEFS – California Emission Forecasting System

CMAQ – Community Multi-scale Air Quality (model)

CO – Carbon Monoxide

EIWG – Emission Inventory Working Group

ICAPCD – Imperial County Air Pollution Control District

IOP – Intensive Operation Period

NOx Nitrogen Oxides

RECLAIM – Regional Clean Air Incentives Market

RRF – Relative Reduction Factor

SANDAG – San Diego Association of Governments

SAPRC – State Air Pollution Research Center

SAQM – SARMAP Air Quality Model

SARMAP – SJVAQS/AUSPEX Regional Model Adaptation Project

SCAG – Southern California Association of Governments

SCAQMD – South Coast Air Quality Management District

SCOS97 – Southern California Ozone Study (1997)

SDCAPCD – San Diego County Air Pollution Control District

SIP – State Implementation Plan

SJVAQS – San Joaquin Valley Air Quality Study

SOx – Sulfur Oxides

TOG – Total Organic Gases

UAM – Urban Airshed Model

USEPA – United States Environmental Protection Agency

VCAPCD – Ventura County Air Pollution Control District

Eight-Hour Ozone Attainment Plan
SCOS Regional Modeling Protocol Document (DRAFT #3, 09/18/00) iv

SCOS97 SPONSORS

Several organizations provided financial and in-kind support to make the 1997

Southern California Ozone Study possible. These organizations were:

California Air Resources Board

Coordinating Research Council

Electric Power Research Institute

Mojave Desert Air Quality Management District

National Renewable Energy Laboratory

Pacific Merchant Shipping Association

Port of Los Angeles

Port of Long Beach

San Diego County Air Pollution Control District

South Coast Air Quality Management District

Steamship Association

United States Marines

United States Navy

United States Environmental Protection Agency

Ventura County Air Pollution Control District

Eight-Hour Ozone Attainment Plan
SCOS Regional Modeling Protocol Document (DRAFT #3, 09/18/00) 1

INTRODUCTION

Background and objectives

During the Summer of 1997 a large-scale field measurement program was carried

out in Southern California to collect sufficient aerometric data to allow data

analysts and modelers to characterize and simulate ozone formation and fate in the

region. Several agencies and others participated during the planning and

operational phases of the field study, including the ARB, the USEPA, the local

districts, the US Navy, the US Marines, and the marine industry. The specific

goals and objectives of the 1997 Southern California Ozone Study (SCOS97) were

two-fold:

1) To update and improve the existing aerometric and emission databases and

model applications for representing ozone episodes in Southern California, with

primary emphasis on high ozone concentrations in the South Coast Air Basin

and secondary emphasis on high ozone concentrations in the San Diego Air

Basin, the South Central Coast Air Basin, the Mojave Desert Air Basin, and the

Salton Sea Air Basin.

2) To quantify the contributions of precursor emissions and of ozone generated

from emissions in one Southern California air basin to federal and state ozone

standard exceedances in neighboring air basins, and to apply modeling and data

analysis methods to design regional ozone attainment strategies.

SCOS97 occurred over a four month period from June 15 – October 15, 1997, and

captured several episodic ozone days. In addition to the SCOS97 data collected, a

severe ozone episode with widespread ozone exceedances occurred during July

1998. This episode is also of planning interest to the regional agencies. Although

data archival and quality assurance activities for the SCOS97 and July 1998 data

are ongoing, it is now time to contemplate the ozone modeling that will be

performed in support of planning needs.

Several ozone nonattainment air basins and regions fall within the planned

modeling domain, and include several potential stakeholder agencies:

Eight-Hour Ozone Attainment Plan
SCOS Regional Modeling Protocol Document (DRAFT #3, 09/18/00) 2

Air Basin/Region Stakeholder Agencies/Region

Mojave Desert Air Basin Mojave Desert Air Quality Management District;

South Coast Air Quality Management District

Northern Mexico Border Region

Salton Sea Air Basin Imperial County Air Pollution Control District;

South Coast Air Quality Management District

San Diego County San Diego County Air Pollution Control District

South Coast Air Basin South Coast Air Quality Management District

South Central Coast Air Basin Santa Barbara County Air Pollution Control

District; San Luis Obispo County Air Pollution

Control District; Ventura County Air Pollution

Control District

Each of the stakeholder agencies is a potential user of the modeling results; all

have been involved to some extent in the planning of the measurement program

and subsequent inventory collection efforts.

The model results are intended to provide technical support to the local agencies in

support of planning needs, primarily the development of comprehensive and

regionally coordinated emission control strategies for attainment of the national

ozone standards. Transport assessment is another planned objective of the

modeling results. Because of the large number of stakeholder agencies, there is a

need for ongoing involvement by all of the agencies to ensure that the modeling

analyses meet their needs in a timely fashion.

This protocol document provides a proposed modeling methodology to be used for

regional 1-hour and 8-hour ozone modeling in Southern California. It describes

the procedures, tools, and analyses that will be used to investigate ozone formation

and transport within the region and, ultimately, to develop and evaluate control

strategies. Although the emphasis of the 2003 State Implementation Plan (SIP)

revision will clearly be on the 8-hour ozone standard, a review of the impact on the

1-hour standard will be performed as resources permit. SIP revisions for the 1-

hour standard may or may not be considered.

We intend for the protocol document to be dynamic, and will update it in response

to reviewer comments and to reflect the results of the modeling analyses.

Eight-Hour Ozone Attainment Plan
SCOS Regional Modeling Protocol Document (DRAFT #3, 09/18/00) 3

MODELING DOMAIN

Previous ozone modeling results in Southern California, such as those in support of

the 1994 State Implementation Plan (SIP), proved sensitive to boundary

concentrations of air pollutants. This reflected the physical processes of

recirculation of pollutants within Southern California and the transport of

pollutants from one air basin to another. However, because of the threedimensional nature of transport and recirculation, it is difficult to take field study

measurements that are adequate to determine boundary conditions. Thus the

boundary conditions used in previous studies were uncertain.

The photochemical modeling studies done for the 1994 SIP for the South Coast Air

Basin, the San Diego Air Basin, and the South Central Coast Air Basin defined the

upper domain boundary at a height of 2,000 m above ground level (AGL) or less.

There were few air quality measurements above this height. However, terrain

elevations in Southern California often exceed 2,000 m AGL and recirculation and

transport above this height are possible. Ozonesonde measurements made during

the 1997 Southern California Ozone Study (SCOS97) have shown high

concentrations of ozone at heights above 3,000 m AGL.

The proposed SCOS97 modeling domain will minimize the influence of boundary

conditions on simulation results and allow the effects of recirculation and

interbasin transport to be better represented by meteorological and photochemical

model simulations. The SCOS97 modeling domain will completely encompass the

South Coast Air Basin and San Diego County, almost all of the South Central

Coast Air Basin (excepting a small piece of San Luis Obispo County),the

California-Mexico border regions, and includes most of the inland desert areas

(Figure 1) to eliminate the need to define boundary concentrations between them.

The domain will extend far enough offshore to contain wind flow patterns

conducive to overwater recirculation. Specifically, the UTM Zone 11 coordinates

of the domain are 150-700 km UTM East and 3580-3950 km UTM North.

Vertically, the modeling domain will extend to a height of at least 5,000 m AGL

for a more complete representation of atmospheric processes. This will contain

observed high ozone concentrations aloft and allow three-dimensional wind flow

patterns near elevated terrain features to be represented better than in previous

simulations, providing more accurate representation of pollutant transport and

recirculation.

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SCOS Regional Modeling Protocol Document (DRAFT #3, 09/18/00) 4

San Luis

Obispo Co.

Santa

Barbara Co.

Kern Co.

Ventura

Co.

Orange

 Co.

Imperial

Co.

Los

Angeles Co.

Riverside Co.

San Diego

Co.

San

Bernardino

Co.

Northern Mexico

Figure 1. The 1997 Southern California Ozone Study photochemical modeling

domain.

Eight-Hour Ozone Attainment Plan
SCOS Regional Modeling Protocol Document (DRAFT #3, 09/18/00) 5

EPISODE SELECTION

Decisions regarding which episode days to model depend on a number of factors,

including peak ozone concentrations and their locations, the type of meteorology,

exceptional events such as large wildfires, and the availability of air quality and

meteorological data. Another consideration is the availability of field

measurements from special studies such as offshore tracer releases.

During the 4 month field study period, the peak observed ozone concentration

within the SCOS97 domain was 21 pphm. There were 13 Intensive Operation

Period (IOP) days during which additional measurements were taken, such as

speciated hydrocarbons and air quality aloft. The peak ozone concentration

measured on an IOP day was 19 pphm. Because of the unique meteorological

patterns during SCOS97 associated with the El Niño phenomenon, there is a

concern that the peak ozone concentrations measured during SCOS97 may not

represent actual design values for Southern California. In July 1998 a severe

regional ozone episode occurred in Southern California with a peak observed onehour ozone concentration in the SCOS97 domain of 24 pphm. Although intensive

field study data are not available for this episode, there were approximately 10

radar wind profilers operating during that period, thereby providing aloft

meteorological data.

Table 1 summarizes the episodes under consideration for regional modeling,

including peak observed ozone concentrations, design values, and other attributes:

Eight-Hour Ozone Attainment Plan
Table 1

Characteristics of SCOS97 and Other Episodes Under Consideration for Modeli

Maximum 1-Hour/8-Hour Ozone Concentratio

Episode Days of Week Episode Type(s) SCAB Ventura San Diego Mojave Desert Santa Barbara IAugust 3-7, 1997 Sunday–Thursday 1-, 2-, 3- 19 / 13.0 13 / 11.5 12 / 9.9 14 / 11.3 10 / 8.7 September 3-6, 1997 Wednesday–Saturday 1-, 2, 3- 16 / 9.9 10 / 7.5 13 / 9.0 10 / 7.7 9 / 7.5 September 21-23, 1997 Sunday–Tuesday 4 11 / 8.8 10 / 8.8 10 / 7.9 7 / 6.1 14 / 10.8 September 26-29, 1997 Friday–Monday 1-, 2-, 4- 17 / 10.7 12 / 9.7 11 / 9.6 10 / 7.7 11 / 9.3 October 30–November 1, 1997 Thursday–Saturday 5 10 / 6.3 11 / 8.1 14 / 11.9 8 / 7.2 9 / 7.6 July 14-19, 1998 * Tuesday–Sunday 1 24 / 20.6 17 / 15.2 16 / 14.2 20 / 14.8 12 / 9.8 1

National 1- and 8-Hour Design Values: 1997!

1998!1999!

21.5 / 14.821.7 / 15.421.1 / 14.7

15.2 / 11.514.4 / 11.213.4 / 10.6

13.8 / 9.9

13.5 / 10.2

13.5 / 9.9

17.5 / 12.416.7 / 12.716.6 / 11.8

13.0 / 8.913.0 / 8.710.8 / 8.2

16

11

State 1-Hour Design Value: 1997!

1998!1999!

242221

151414

131313

161816

111110

Episode Types1 South Coast Air Basin ozone maximum2 upper level transport to San Diego3 secondary South Coast Air Basin ozone maximum with transport into Mojave Desert4 eddy transport to Ventura following episode in South Coast Air Basin5 off-shore surface transport to San Diego* There is no aloft air quality data available for the July 1998 episode.

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SCOS Regional Modeling Protocol Document (DRAFT #3, 09/18/00) 7

We propose to simulate several multi-day ozone episodes, as discussed below.

Synopses of the meteorology associated with each of the 1997 episodes can be

found in the summary of SCOS97 field operations (ARB et. al, 1998).

The following episodes are proposed as primary episodes for the regional modeling

effort, pending further discussion with the stakeholders:

• The SCOS97 episode period of August 3-7, 1997. This episode was selected

because the peak 1-hour ozone concentration of 19 pphm and the peak 8-hour

concentration of 12.5 pphm measured in the South Coast during this period

were the highest not associated with an exceptional event during SCOS97.

High ozone concentrations were also observed in other areas, as indicated in

Table 1.

• The SCOS97 episode period of September 26-29, 1997 was selected because it

includes the second highest ozone concentrations measured during an IOP, and

it represents a weekend episode. The peak 1-hour (17 pphm) and 8-hour (10.7

pphm) ozone concentrations were both observed at Upland. The 17 pphm value

represents the second highest episodic ozone concentration observed during a

SCOS97 intensive operating period.

• The SCOS97 episode period of September 3-6, 1997 was selected because it

includes the highest 1-hour ozone concentration (13 pphm) measured during an

IOP in San Diego, and because of the availability of offshore tracer release data

for windfield validation.

• The non-SCOS July 14-19, 1998 episode was selected because it represents a

severe, widespread high ozone event in the region. The peak observed 1-hour

ozone concentration in the South Coast Air Basin was 24 pphm; an 8-hour peak

of 20.6 pphm was also observed. Other areas also experienced elevated ozone

peaks, including San Diego (1-hour peak of 16 pphm), Ventura (1-hour peak of

17 pphm, 8-hour peak of 15 pphm), and Mojave Desert (1-hour peak of 20

pphm, 8-hour peak of 14 pphm).

In addition to the primary episodes listed above, the September 21-23, 1997 and

the October 30-November 1, 1997 episodes are also of potential planning interest,

and will be considered based upon stakeholder input and the availability of

resources.

Eight-Hour Ozone Attainment Plan
SCOS Regional Modeling Protocol Document (DRAFT #3, 09/18/00) 8

AIR QUALITY MODEL SELECTION

The Urban Airshed Model (UAM-IV) is the only Eulerian photochemical

modeling tool that has been previously approved by the USEPA for ozone

modeling studies. However, the UAM-IV (USEPA 1990) is widely acknowledged

to have characteristics which limit its utility when applied to large modeling

domains, or to domains that are not geographically uniform. In addition, much of

the science in the model is not up to date, and both the USEPA and the ARB are

contemplating removing that model’s recommended status. A number of

photochemical models have been developed over the last decade to improve upon

the UAM-IV; these include:

• CALGRID (Yamartino et. al, 1989). The CALGRID model was developed for

the ARB in the late 1980's. The model has been applied by various air pollution

agencies around the world. It is modular to allow the user to substitute various

types of wind fields and chemical mechanisms. CALGRID incorporates refined

treatments of numerical advection, vertical transport and dispersion, and dry

deposition. The model can be exercised with either the Carbon Bond IV or

SAPRC chemical mechanisms, and contains highly efficient chemical

integration routines. The vertical structure of the atmosphere can be optionally

defined relative to a mixing height field, similar to the UAM, or can be based

on fixed layer heights and a derived mixing height.

• The Comprehensive Air-Quality Model with Extensions (ENVIRON 1997).

CAMx contains a number of advanced features, including grid nesting, subgrid-scale plume-in grid simulation, alternative numerical advection solvers,

and the ability to use alternative chemical mechanisms. In addition it has the

ability to tag emissions so that at the end of the simulation one can determine

the sources of emissions impacting a particular receptor. Since CAMx is a

relatively new model, there is a relatively short history of experience applying

the model.

• Models-3 (USEPA 1998a). Models-3 is a flexible software system designed for

applications ranging from regulatory and policy analysis to understanding the

complex interactions of atmospheric chemistry and physics. The MODELS-3

system allows the user to go from developing model inputs to visualizing

results all in one package. At the heart of the current version of MODELS-3 is

the Community Multi-scale Air Quality (CMAQ) model. Its capabilities

include urban to regional scale air quality simulation of ozone, acid deposition,

visibility, and fine particles. CMAQ is a modular system capable of using

output from the MM5 prognostic meteorological model, along with the CBIV

Eight-Hour Ozone Attainment Plan
SCOS Regional Modeling Protocol Document (DRAFT #3, 09/18/00) 9

or RADM-2 chemical mechanism. The CMAQ model also includes a plumein-grid module, vertical and horizontal growth due to turbulence and shear, a

choice of advection schemes, and a cloud- module to simulate precipitating and

non-precipitating clouds. A forthcoming aerosol module will allow simulation

of PM2.5 and PM10. Since the Models-3 system is new, some implementation

and application problems are likely.

• SARMAP Air Quality Model (J.S. Chang et. al, 1997). SAQM is a threedimensional non-hydrostatic model based upon the Regional Acid Deposition

Model (Chang et. al 1987, 1990). However, SAQM includes a number of

improvements over RADM, including: a fixed vertical coordinate system that is

compatible with MM5; a horizontal coordinate system defined in a LambertConformal projection that accounts for curvature of the Earth; a mass

conservation module for compatibility with non-hydrostatic meteorological

inputs; the Bott advection scheme (Bott 1989a, 1989b) to reduce numerical

diffusion and increase numerical accuracy; two-way nesting, and the capability

to use either the CBM-IV or SAPRC chemical mechanisms. A version of

SAQM with plume-in-grid treatment is also available.

• Urban Airshed Model-Flexible Chemical Mechanism (Kumar et. al, 1995). The

UAM-FCM is an alternate version of the UAM-IV that has been enhanced to

allow the flexibility to incorporate any Carbon Bond- or SAPRC-type chemical

mechanism. The FCM allows incorporation of reaction-specific photolysis

rates. In addition, the UAM-FCM has a generalized methodology to solve the

set of differential equations that is mechanism independent.

• Urban Airshed Model-V (SAI 1996). The UAM-V (UAM-V) is an updated

version of the Urban Airshed Model (UAM-IV) which incorporates many

state-of-the-art enhancements in chemical mechanisms, meteorological models,

and representation of emissions. Perhaps the most significant additions are: an

updated CB-IV mechanism to include aqueous phase chemistry; plume-in-grid

capabilities; an improved dry deposition algorithm; and an improved plume rise

algorithm. Other enhancements over UAM-IV include allowing the user a

fixed vertical structure as opposed to one that is relative to the diffusion break,

the ability to use three dimensional inputs from prognostic models, and twoway grid nesting. However, the present non-public domain status of UAM-V

precludes regulatory usage.

As part of their joint preparation of a year 2000 AQMP, the staffs of the ARB and

the SCAQMD have agreed to begin the testing of a number of the available models

for the SCOS97 domain: CALGRID, UAM-V, CAMx, UAM-FCM, Models-3 and

SAQM. This testing will provide experience using each model. The experience

Eight-Hour Ozone Attainment Plan
SCOS Regional Modeling Protocol Document (DRAFT #3, 09/18/00) 10

gained during this exercise will allow us to narrow the list of candidate models for

application to 8-hour ozone modeling in the SCOS97 region. If appropriate, more

than one air quality model will be used as the basis for attainment planning

activities in the region.

The models will be run using the Carbon Bond IV chemical mechanism (Gery et.

al, 1989), which is the most widely used mechanism. However, the ARB

anticipates making additional simulations with the SAPRC mechanism

(Carter1990; Carter et. al, 1993; Carter 1995; Carter et. al, 1996; Carter et. al,

1997; Carter et. al, 1999) for comparison purposes. The SAPRC chemical

mechanism is the basis for chemical reactivity scales.

Eight-Hour Ozone Attainment Plan
SCOS Regional Modeling Protocol Document (DRAFT #3, 09/18/00) 11

HORIZONTAL AND VERTICAL GRID RESOLUTION

Horizontal Grid Resolution

Over the past decade, photochemical models have been applied in California with

horizontal grid resolutions in the range from 2 x 2 km to 8 x 8 km. The specific

grid resolution chosen was primarily dependent on the size of the modeling

domain, computer resources available, and the time and money available to carry

out the simulations. In effect the final resolution was a compromise between the

accuracy desired and the cost. However, the current generation of high-speed

computers have minimized cost and resource constraints.

The horizontal grid resolution plays an important role in the modeling process.

Large grid resolution tends to smooth emission gradients and meteorological

inputs, which in turn leads to a smoothing of the resulting concentration fields. In

general, the resolution should be sufficiently small to pick up emission gradients in

urban areas and be consistent with the major terrain features which may affect the

air flow.

• Air Quality Modeling

For the SCOS97 modeling, we propose to use a horizontal grid resolution of 5 km

for the air quality modeling. No grid nesting is anticipated. This resolution is

consistent with the grid resolution used in earlier photochemical modeling studies

for the South Coast Air Basin (e.g., SCAQMD, 1994) and for San Diego. For the

proposed SCOS97 modeling domain, use of a 5 km resolution results in a

modeling grid with 110 cells in the east-west direction, and 74 cells in the northsouth direction. The SAQM model will be based on a Lambert-Conformal map

projection system, and thus will use a slightly different domain; all other air quality

models will use a UTM-based horizontal coordinate system.

• Meteorological Modeling

Meteorological inputs to the air quality model will be provided for the same

horizontal grid resolution and coordinate system (i.e., UTM or Lambert

Conformal). More details of the meteorological modeling can be found in the

section “METEOROLOGICAL INPUTS.”

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SCOS Regional Modeling Protocol Document (DRAFT #3, 09/18/00) 12

• Emission Inventory

The emission inventory is based on a UTM coordinate system, with a horizontal

resolution of 2 km. For SAQM, the emissions will be mapped from UTM into a

Lambert Conformal coordinate system. More information on the inventory can be

found in the section entitled “EMISSION INVENTORY.”

Vertical Resolution

As with the selection of the horizontal grid resolution, the vertical resolution

defined for photochemical modeling domains has been limited by computational

resources. In addition, available aloft meteorological and air quality databases

were not sufficient to characterize conditions aloft. As a result, simulation results

have been limited by the relatively few number of vertical layers within the surface

mixed layer, resulting in poor representation of the stratification of the atmosphere.

As enhanced aerometric databases have become available—such as the 1990 San

Joaquin Valley Air Quality Study and 1997 SCOS97—more has been learned

about the vertical structure of the atmosphere. The ability to better simulate the

vertical structure of the atmosphere is emerging due to the availability of

measurements aloft, the emergence of higher-speed computers, and our increased

experience with diagnostic and prognostic meteorological models.

• Air Quality Modeling

To improve on the representation of the vertical structure of the atmosphere for the

SCOS97 modeling, the number of vertical layers below 500 m (the nominal height

of the afternoon mixing height within the Los Angeles coastal plain) will be

increased over previous studies, and the modeling domain top will be set to a

height of at least 5,000 m.

CALGRID – 16 vertical layers will be used, to a height of 5,000 m. The vertical

layering will be the same as that used by the CALMET model (see Table 3).

CAMx – The fixed height vertical layers will be the same as for CALGRID.

UAM/FCM – As for the UAM, the vertical atmosphere is defined in two zones:

that above the mixing height and that below. A total of 5-8 vertical layers are

proposed for the SCOS97 simulations.

Models-3 – Since we are in the process of installing and implementing Models-3,

its vertical structure has not yet been defined.

Eight-Hour Ozone Attainment Plan
SCOS Regional Modeling Protocol Document (DRAFT #3, 09/18/00) 13

SAQM – 15 vertical layers will be used, to a height of 100 mb or approximately

15 km. Table 2 shows the proposed SAQM layering.

Table 2Proposed vertical layer heights for SAQM

Layer # Height (m)*

1................... 61

2.................. 153

3.................. 262

4.................. 388

5.................. 516

Layer # Height (m)*

6.................. 645

7.................. 776

8.................1,077

9.................1,528

10................2,207

Layer # Height (m)*

11................4,032

12................5,083

13................7,270

14...............10,499

15...............15,634

* These height estimates are based on sigma-level calculations at sea level using

standard conditions. Height increments will decrease as terrain elevation

increases.

• Meteorological Modeling

For the terrain-following CALMET model, the proposed vertical layer definition is

shown below.

Table 3

Proposed vertical layer heights for CALMET/CALGRID

Layer # Height (m)*

1.................20.0

2.................60.0

3................100.0

4................300.0

5................400.0

6................400.0

Layer # Height (m)*

7 ............... 600.0

8 ............... 800.0

9 ..............1,000.0

10 .............1,500.0

11 .............2,000.0

Layer # Height (m)*

12 ..............2,500.0

13 ..............3,000.0

14 ..............3,500.0

15 ..............4,000.0

16 ..............5,000.0

* Heights are for a constant-height, terrain-following coordinate system

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For the MM5 prognostic model, the following vertical structure is proposed.

Table 4

Proposed vertical structure for MM5

Level Height (m)*

30................. 61

29................ 154

28................ 263

27................ 389

26................ 516

25................ 646

24................ 776

23................ 926

22............... 1077

21............... 1300

Level Height (m)*

20 ............. 1528

19 ............. 1862

18 ............. 2207

17 ............. 2714

16 ............. 3228

15 ............. 3837

14 ............. 4452

13 ............. 5083

12 ............. 5816

11 ............. 6551

Level Height (m)*

10..............7270

9...............7981

8...............8773

7...............9624

6..............10499

5..............11371

4..............12230

3..............13227

2..............14334

1..............15635

* The vertical coordinate system for MM5 is based on a normalized pressure

scale. The above layer heights were calculated from sea level using standard

conditions. Layer heights are lower relative to ground level as terrain height

increases.

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METEOROLOGICAL INPUTS

Air quality models require three-dimensional meteorological inputs. The key

parameters are winds, mixing heights, temperature, and insolation. The windfields

describe the transport and dispersion of pollutants. Mixing heights define the

vertical extent of pollutant mixing near the surface. Temperature and insolation

fields influence emission rates and the rates of chemical transformation. Because

meteorological measurements can only be made at discrete locations,

meteorological models are required to develop the 3-dimensional fields required by

models.

The meteorological models used to generate these three-dimensional fields are

generally of three types: objective, diagnostic or prognostic.

Objective models are the least sophisticated meteorological models. The analysis

consists of interpolation of observations. Obtaining a reasonable field requires

sufficient observations to accurately represent the observed pattern(s). This is

especially true for windfields. In areas with complex terrain and bodies of water,

such as the SCOS97 domain, the meteorology can be quite complex, and a

successful objective analysis would require a large number of observations.

Diagnostic models rely on observations, yet apply constraints based on physical

concepts such as the conservation of mass. A diagnostic wind model can simulate

thermally induced circulations and the effects of surface friction. One example of

this type of model is the Diagnostic Wind Model (DWM) distributed by the

USEPA. For the DWM, the user defines first an initial guess mean wind field that

can be representative of synoptic scale patterns. The domain mean wind is then

adjusted for the effects of terrain. Available observations are then used to develop

meteorological fields using objective analysis. The initial guess and the objective

analysis are then merged. A criticism of diagnostic models is that the fields

produced are not consistent from one hour to the next. Since the processes which

create the wind, temperature, and mixing height fields are relatively independent,

the model is criticized for not being thermodynamically consistent between the

meteorological parameter fields.

Prognostic models are the most sophisticated of the meteorological models. They

are based on first principles, i.e., conservation of mass, momentum, energy and

moisture. As a result they are computationally intensive. The use of four

dimensional data assimilation (FDDA)–where observations are introduced to the

model as an additional forcing term–is typically used in areas of complex

meteorology to improve the accuracy of the outputs. Another approach is

objective combination, in which observations are introduced after the model has

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estimated a value. Prognostic models are capable of explicitly incorporating many

of the physical flow processes important in the SCOS97 domain. However,

prognostic models have historically had problems estimating fine-scale flow

features due to the limited resolution of datasets used for describing geographic

features

Previous Applications

In the past, the ARB and SCAQMD have utilized prognostic, diagnostic, and

objective models to generate meteorological inputs for modeling. The National

Center for Atmospheric Research’s prognostic, non-hydrostatic Mesoscale Model

(MM5) was applied for modeling in support of attainment planning in the San

Joaquin Valley. The SCAQMD also has experience with the SAIMM prognostic

model. Diagnostic models (WIND2D, WIND3D, DWM) have been applied in the

Sacramento area and in Southern California to prepare meteorological input fields

for the application of photochemical models in those areas. The ARB and the

SCAQMD have also begun a review of CALMET, which may be viewed as an

improved version of the DWM and which is being distributed through the USEPA

for air quality modeling applications. The CALMET model has an added feature

that allows a hybrid meteorological field to be developed by merging the results

from a prognostic model, such as MM5, with an objective or diagnostic analysis

characteristic of the CALMET model. This hybrid approach has the potential to

take advantage of the prognostic capabilities of MM5 in areas of the domain where

meteorological measurements are few, and utilizing measurements in an objective

analysis where there are many.

Proposed Approaches

The SCOS97 field study generated a dataset with a relatively high spatial density

of meteorological observations. While this dataset suggests that an

objective/diagnostic model would be adequate to develop the meteorological

parameter fields required for air quality modeling, there are large portions of the

SCOS97 modeling domain—such as over the ocean or the inland desert—where

there are few observations. Therefore, three approaches are proposed to develop

the necessary meteorological fields. After the fields have been developed using

each approach, they will be evaluated to determine which is the most suitable for

air quality modeling.

• Diagnostic Modeling

The first approach will be to use the diagnostic meteorological model CALMET.

As described previously, CALMET uses a fixed-height, terrain-following

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coordinate system. For the SCOS97 modeling, 16 vertical layers will be used to a

height of 5,000 m above the ground (see Table 2).

• Prognostic Modeling

The second approach will be to use the MM5 prognostic model. The

meteorological boundary conditions for MM5 are generated using the output from

a Global Climate Model (GCM) with a relatively coarse grid scale of 45 km.

Nested domains of 15 km and 5 km are then defined within MM5 to simulate

meteorological fields for the fine grid scale of the SCOS97 modeling domain. The

modeling domain for MM5 is defined in a Lambert-Conformal projection with two

parallels to account for curvature of the Earth within the modeling domain over

such a large region. Figure 2 shows the nested MM5 domains. Figure 3 shows the

finest scale (interior) MM5 domain.

The vertical structure of MM5 is defined in a terrain-following, “sigma” coordinate

system based upon a normalized pressure index. The 30 vertical layers defined for

MM5 (see Table 3) can be transformed to fit the requirements of any air quality

model.

• Hybrid Approach

The third approach for developing meteorological parameter fields will be to

combine the results of the CALMET and MM5 models into a hybrid

meteorological field. In this approach, the parameter fields will be overlaid using a

weighting scheme that is based on the proximity to meteorological observations.

The resultant fields benefit from the capabilities of the prognostic model in those

areas of the modeling domain with few observations (such as offshore, in complex

terrain, and in the desert areas), and benefit from the objective analysis component

of the diagnostic model to force the fields to agree with observations. To develop

the hybrid fields, the fields developed using CALMET and MM5 will need to be

mapped into common horizontal and vertical coordinate domains. The CALMET

model code is structured to facilitate this mapping.

Meteorological Input Validation and Technical Review

The meteorological inputs have a profound influence on the spatial and temporal

resolution of ozone and other pollutant concentrations estimated by the air quality

model. It is therefore essential that the products of meteorological models undergo

a rigorous evaluation. By evaluating both offshore and onshore flow

characteristics of the windfield and other key meteorological parameters we can

minimize the uncertainty in the air quality simulations.

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This process includes an evaluation of the gross circulation features in the

modeling region to determine if the model is replicating those essential features

(Mulberg, 1995, Lolk and Douglas, 1996). These features include areas of

convergence and divergence, eddy circulations, land/sea breeze, slope flows, and

transport corridors. Since the SCOS97 domain includes large overwater areas it is

also necessary to evaluate offshore flows as well.

Key features of the windfield are areas of convergence and divergence. These

features result in vertical velocities which can transport pollutants upward (in the

case of convergence) or bring pollutants from aloft down to the surface (with

divergence). The evaluation should include a review of the convergence and

divergence zones in the simulated windfield to determine if they agree with

measurements or conceptual models in terms of location, timing, and extent. The

impact on vertical velocities should also be evaluated.

Converging flows can sometimes result in an eddy circulation. In the SCOS97

domain two key eddy features are prevalent: the Catalina eddy (centered near

Catalina Island), and the Gaviota Eddy in the Santa Barbara Channel (Smith, et.

al., 1984). Both eddy circulations are important transport mechanisms; they are

capable of transporting precursors and aged ozone concentrations onshore.

Exceedances of the ozone standards are often observed with the presence of an

eddy circulation. The timing of the onset of eddy circulation, its persistence, and

spatial extent should be considered as part of the windfield validation.

Land/sea breeze circulations are another important flow feature. The sea breeze is

one method whereby pollutants generated in the Los Angeles Basin are transported

eastward. That is, the strength of the sea breeze will determine how far precursors

and ozone generated near the coast will be transported inland. Errors in the timing

of the sea breeze can cause precursor emissions to be transported to the wrong

locations instead of inland where peak concentrations are observed. It is thus

essential that the onset of the sea and land breezes simulated by the model be

compared to observations for reasonableness.

The onshore portion of the SCOS97 domain includes areas of complex terrain.

Slope flows are important as a recirculation mechanism that may influence ozone

concentrations. Slope flows are probably the most challenging feature for

prognostic meteorological models, due to the sparse observational data in complex

terrain. A proposed qualitative approach is to determine if wind speeds estimated

by the model appear to be reasonable in areas of complex terrain.

Transport of ozone and precursors from the Los Angeles area to outlying areas is

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an obvious mechanism of interest to the regional stakeholders. Provided that the

observational data support transport, the generated windfield(s) should allow us to

evaluate transport couples of interest. Specifically we are interested in transport

from Los Angeles to the desert areas, from Los Angeles to San Diego, from Los

Angeles to Ventura and Santa Barbara, from Mexico to San Diego, and from San

Diego to Mexico. These evaluations can be made by calculating trajectories both

at the surface and aloft with the simulated windfield, and comparing to

observations and conceptual models based on the observations.

As a qualitative and quantitative evaluation of the windfields, we propose to

statistically summarize and plot wind speeds by site and globally throughout the

SCOS97 domain (Seaman et. al., 1995, Bigler-Engler et. al., 1996). Temporal

plots for agreed upon key sites will be examined to determine agreement with

observations. Quantitative techniques will make use of statistical measures such as

the mean gross error and mean bias to compare modeled and measured wind

speeds (Mulberg, 1995).

The proposed approaches for generating meteorological inputs incorporate

observations, thus we should expect good agreement near those observation sites

where data was used as input to the model. In order to diagnose the impact that

incorporation of the observations has on the meteorological models, it may be

useful to consider withholding some observations when executing the models to

have an independent set of observations for comparison. The sites withheld should

have some relation to the sites used to provide some assurance in the results from

the comparison. We propose to conduct this diagnostic evaluation once acceptable

meteorological fields have been prepared.

Temperature fields will also be examined. At the surface, qualitative analyses will

include an examination of the temporal and spatial variation of estimated and

observed temperatures. The interface at the coastline will also be examined. Mean

bias and mean gross error statistics will also be calculated to provide quantitative

measures of performance.

In addition, the vertical temperature profiles generated by the models will be

compared to those observed at rawinsonde sites, at wind profiler locations, and

from aircraft spirals. The vertical temperature profile influences the stability

characteristics of the modeling domain. One of the most notable affects is on

mixing heights. The evaluation will include temporal and spatial evaluations of

simulated mixing heights as compared to those estimated from observed soundings

and profiler data. The timing of the onset and breakup of the inversion will also be

evaluated, as this phenomenon has a profound effect on estimated ozone

concentrations.

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Figure 2

Nested MM5 Domains

The horizontal grid resolution of the outermost domain is 45 km, for the middle

domain is 15 km, and for the fine scale domain is 5 km.

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Figure 3

The Fine-Scale (5 km) MM5 Domain.

-10

-10

1000

1000

1000

1000

1000

1000

1000

1000

1000

1000

1000

1000

1000

1000

1000

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EMISSION INVENTORY

Ozone episodes occurring in both 1997 and 1998 will be simulated for the SCOS97

modeling domain. Base year inventories for CO, NOx, SOx, and TOG are needed

for ozone modeling. PM is also included in the inventory in order to support

inputs needed for aerosol modeling. Photochemical air quality models require

gridded, hourly emissions. The information needed to complete the emission

inventory for the SCOS97 modeling region is obtained from local air pollution

control districts, transportation planning agencies, and the California Air Resources

Board. In addition, contracts have been established with universities and the

private sector to provide important inventory components.

To develop an emission inventory for SCOS97, an Emission Inventory Working

Group (EIWG) was formed. The EIWG is comprised of members from the ARB,

SCAQMD, SDCAPCD, VCAPCD, ICAPCD, MDAQMD, SBCAPCD, and US

Navy (ARB 1997a).

Anthropogenic Emissions

• Point Sources

Emissions for point sources (including RECLAIM facilities) are inventoried by

local districts and reported to the ARB. If annual emissions for a facility fall

below 10 tons/year (this cutoff varies with district) the source is included in the

area source inventory. Point sources are allocated to grid cells using the location

that is stored as part of the point source emission database. Temporal codes which

describe hours of operation are also included in the emission database. Factors are

also stored to convert annual average emissions to a specific month and day of

week.

Point sources have been inventoried for 1996. The SCAQMD is working on a

point source inventory for 1997 which will include an update to locations (UTM

coordinates) and stack parameters. Santa Barbara and Ventura Counties have

submitted their 1997 annual average inventory; 1997 data from other districts will

also be incorporated if available in time. Most other point source emissions will be

“grown” to 1997 from 1996 emission values using ARB’s California Emission

Forecast System (CEFS). Point source emissions for 1998 will also be estimated

using the CEFS (M. Johnson, 1997).

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• Area Sources

Area sources are comprised of emission source types that are difficult to inventory

individually. Examples are architectural coatings, residential water heating,

gasoline stations, and off-road mobile sources not included in the OFFROAD

model. Districts and the ARB share responsibility for estimating area source

emissions. Methodologies used to estimate emissions from area sources are

described in several documents (ARB 1997b). Factors are also included that allow

estimates of specific month and day of week emissions from annual average

emissions. Temporal codes which describe hours of operation are also included in

the area source emission database.

Area source categories have been inventoried for 1996. Emissions for 1997 and

1998 (except for eight ARB categories that were updated in 1997) will be grown

using CEFS, except for Santa Barbara and Ventura Counties, since these counties

have already submitted their 1997 annual average inventory.

• On-Road Mobile Sources

On-road mobile source inventories are prepared using vehicle activity data from

transportation planning agencies. The majority of travel is reflected in

transportation plans developed by:

1) Southern California Association of Governments (SCAG);

2) San Diego Association of Governments (SANDAG);

3) Santa Barbara County Association of Governments (SBCAG); and

4) Kern Council of Governments (Kern COG).

Travel for areas not covered by the transportation planning agencies is extracted

from the California Statewide Planning Model maintained by the California

Department of Transportation.

Emission factors for on-road mobile sources will be estimated using the ARB’s

EMFAC99 emission factor model. DTIM3 will use both the emission factors and

travel activity data to produce hourly gridded emission estimates for the SCOS97

region. EMFAC7G, the current ARB emission factor model, is being updated and

will be replaced by EMFAC99. DTIM3 has undergone testing with EMFAC7G

but is not compatible with EMFAC99. The needed changes to DTIM3 are in

progress. If delays are encountered, DTIM3 can be used to grid on-road mobile

source emissions with EMFAC7G emission factors. The gridded inventory can

then be scaled to be consistent with EMFAC99 using scaling factors specific to

source category, time, and location.

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The ARB has contracted with STI to acquire all travel data needed for this

modeling study. STI will ensure that the digitized highways are consistent at the

boundaries of the various planning areas. The network and travel activity data

provided by transportation planning agencies is developed for peak and off-peak

time periods, which will be processed into 24 hourly data sets. The results from a

U.C. Davis project (that is nearing completion) to incorporate traffic count data

from episode days will be used to calibrate DTIM3 inputs. STI will run the

DTIM3 program to develop mobile source inventories for several episode days,

including weekend days.

ARB staff will use the network and travel activity data to produce DTIM3

inventories for episode days not run by STI. One of STI’s tasks is to provide

training in processing inputs and executing the DTIM3 code.

• Other Mobile Sources

Area source emissions from most categories of off-road mobile sources will be

estimated using ARB’s off-road mobile source emission model (OFFROAD).

OFFROAD covers more than 12 off-road categories, including lawn and garden

equipment, small utility and construction equipment, as well as farm equipment.

Categories not estimated by OFFROAD will be covered under “area sources”.

OFFROAD will produce countywide emission inventories for each calendar year

desired. The OFFROAD model will have the capability to estimate exhaust,

starting, and evaporative emissions for differing spatial and temporal conditions.

• Day-Specific Emissions

Emissions from many sources vary from day to day. Evaporative emissions from

vehicles and vegetation increase with ambient temperature. Exhaust emissions are

also a function of ambient temperature. Increased air conditioning demands on hot

days also lead to increased emissions from electrical generation. Hourly surface

temperatures for episode days are interpolated to each grid cell and are used in

estimating emissions on-road mobile sources.

Criteria pollutant emissions from approximately 80 major point sources will also

be estimated hourly for each specific episode day. Each district has acquired data

from major point sources for 1997 episode days and has already finished or is

developing day-specific point source inventories for that year. Day-specific data

for the July 1998 episode have been solicited from the districts. Districts also

collected information on variances, temporary breakdowns, and shutdowns.

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Wildfire emissions occurring on 1997 and 1998 episode days have been compiled

by ARB staff, and hourly emissions have been estimated for each wildfire. The

type of information collected will allow development of temporally and spatially

resolved emission estimates.

A computer model to estimate emissions from large ships in the SCOS97 modeling

domain is being developed by ARB staff. Ship activity data (for commercial

vessels) from shipping ports, ship-specific engine characteristics, and the latest

emission factors will be used to estimate emissions for transit in the shipping lanes

and at the ports.

The ARB has purchased aircraft activity data for the SCOS97 and July 1998

episode days. This data has one minute radar-derived locations for all aircraft in

the SCOS97 region. Hourly landing, takeoff, approach, climbout, and cruise

emissions can be determined from these data for each episode day. This database

will be used to construct a three dimensional aircraft emissions array that can be

input to photochemical models.

An analysis of air quality-related special events (such as air shows, sporting events,

fires, and unusual traffic problems) has turned up an absence of such events.

Natural Emissions

• Biogenics

The derivation of a gridded biogenic emission inventory requires data sets

describing the spatial distributions of plant species, biomass, and emission factors

that define rates of hydrocarbon emissions for each plant species. The Biogenic

Emission Inventory System (BEIS 2.3) (USEPA, 1995) model, distributed by the

USEPA for this purpose, is one source of these data sets for areas throughout the

United States. However, the BEIS model has been shown to have limited use in

California because of poor spatial resolution within the referenced data sets and a

simplified scheme for assigning emission factors (e.g., Jackson, et al., 1996). The

development of a gridded biogenic emission inventory for the SCOS97 domain

will benefit from research conducted within California that describes the needed

data sets in more detail than is defined within the BEIS model (Benjamin et. al.,

1998).

ARB staff in consultation with Dr. Arthur Winer of UCLA has developed a

methodology to complete a gridded biogenics inventory for the SCOS97 region.

The following paragraphs describe this approach.

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Gridded Plant Species Maps

The distribution of plant species within the SCOS97 modeling domain will be

determined using a composite of a number of data sets. Plant species as a function

of urban land-use classifications were described by SCAQMD (1990) for the Los

Angeles basin and updated by Benjamin et. al. (1996) and Arey et. al. (1995).

These land-use classifications were extrapolated to other urban areas within the

modeling domain. For the SCOS97 modeling domain, plant species distributions

were taken from the GAP data base (Davis et. al. 1995), an inventory of biomass

diversity for the United States.

Biomass Distribution

Plant biomass is difficult to measure and there are few descriptive data sets of

biomass distribution for areas within the SCOS97 modeling domain. Therefore,

estimates of biomass distribution were determined using published correlations

between biomass and Normalized Difference Vegetative Index (NDVI). The

NDVI is an index of relative "greenness" calculated from Advanced Very High

Resolution Radiometer (AVHRR) data. Spatial distribution of NDVI from satellite

remote sensing data sets were acquired from the United States Geological Survey

EROS Data Center.

Emission Factors

The chemical species and rates of hydrocarbon emissions vary by plant species.

Emission factors have been measured for only a relatively small subset of the more

than 6,000 plant species known in California, and for only a few general categories

of chemical species. However, research has shown that emission factors for

various plant species can be correlated using taxonomic relationships between the

plant species (Benjamin et. al., 1996). Using this “taxonomic model”, emission

factors were assigned for all plant species known to exist within the SCOS97

modeling domain. However, because of the limited research results available,

biogenic emission factors are available for only 2 classes of hydrocarbons:

isoprene and monoterpenes.

Gridded Biogenic Inventory

The gridded plant species, biomass distribution, and emission factor databases will

be combined with episode-specific ambient temperature and photosynthetically

active radiation data using a Geographic Information System to produce gridded

hourly emissions of isoprene, monoterpenes, and methylbutenol.

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• Soil NOx Emissions

Soil emissions of NOx to the air have been associated with the use of nitrogen

containing fertilizers. Emissions have been estimated from fertilizer usage in the

San Joaquin Valley. The soil NOx emissions were seen to have insignificant

impacts on ozone concentrations. As a result, a soil NOx inventory has not been

planned for this study.

• Oil and Gas Seeps

There are substantial emissions from oil and gas seeps near the coast in the areas of

Santa Barbara and Ventura counties. Estimates for these sources are provided to

the ARB by the respective counties.

Organic Gas Speciation

Organic gas speciation profiles are applied to all categories of TOG emissions to

obtain estimates for each organic gas species emitted in the modeling region. ARB

maintains a database of current profiles that are routinely updated to reflect recent

information. The most recent updates were for gasoline exhaust and evaporation,

diesel exhaust and jet engine exhaust. These recent updates were presented at the

September 10, 1998, VOC Speciation Workshop held in Sacramento. The ARB

publication “Identification of VOC Species Profiles” (ARB 1991) documents the

organic gas profiles; an update is planned by summer 1999 to reflect the recent

workshop.

Gridding Surrogates

Area and OFFROAD emissions are estimated and stored in the emission inventory

database at the county level. There are many types of data (with highly resolved

spatial resolution) that can be used as surrogates for one or more emission

categories. For example, census tract population can be used to allocate consumer

product emissions to grid cells. Housing units, also available for census tracts, can

be used to spatially allocate residential lawn and garden equipment emissions.

Maps are used to digitize and spatially allocate emissions for several categories of

watercraft, locomotives, and airports.

The ARB has contracted with STI to provide gridded surrogates for all area and

off-road mobile source emission categories. STI will seek inputs from the districts

and the ARB on the appropriate gridding surrogates to use for each emission

category for the SCOS97 region.

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SCOS97 surrogates are being resolved to a 2 kilometer grid scale to allow high

spatial resolution if needed. The 2 kilometer inventory can easily be aggregated to

larger grid cells.

Northern Mexico Inventory

A portion of northern Mexico is included in the SCOS97 modeling region. A

gridded inventory for this region was developed by SAI (SAI 1997) as part of a

study to develop a 1990 gridded inventory for the region. Another contractor, STI,

will review and recommend updates to the SAI gridded inventory for Northern

Mexico. Organic gas emissions will be speciated using the most appropriate

species profiles used for California emission categories.

Quality Assurance Procedures

ARB provided specific guidelines to assist state and local agencies in

implementing uniform and systematic approaches for collecting, compiling, and

reporting emission inventory data. A comprehensive quality control and quality

assurance plan was prepared to ensure good quality practices during development

of 1996, 1997, and future year emission inventories. These procedures include:

quality control checks for collecting non-emission data, updating activity data, and

using appropriate emission factors for calculating emissions; emission calculation

methodology; quality assurance evaluation using the Data Attribute Rating System

(DARS); and quality review of the entire inventory. The DARS program,

originally developed by the USEPA, will be used as an additional quality assurance

tool to quantify the relative accuracy of the annual emission inventories. ARB has

also provided the districts with a variety of quality assurance reports to aid in the

review of inventory data important for modeling. These reports were intended to

provide checks on the accuracy of the emission calculations, stack data, facility

location data, temporal data, devices data, process data, etc.

Emission Projections

Future year emissions form the basis for an air quality emission reduction target.

Control measures and growth factors are applied to base year (1997) area and point

source emissions to project future year emissions. Area source emissions are

gridded using the appropriate surrogates as used for 1997. STI is also preparing

gridded future year surrogates for the entire SCOS97 region for 2005, 2010, and

2020. Surrogates for other years can be interpolated as needed.

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Future year traffic activity and network data are also prepared by local planning

agencies. EMFAC99 will give estimates of future year emission factors. DTIM3

uses future year emission factors and network travel data to obtain gridded future

year on-road mobile emissions. DTIM3 inputs for future years are being compiled

and prepared (for DTIM3 input) by STI under contract to the ARB. Ambient

temperatures that occurred during 1997 are also used in calculating future year

emissions for each episode day.

Biogenic emissions will remain constant for each episode day for all future years.

Even though there may be a shift in farm or landscaping plans and species, we do

not have the capability to incorporate any potential changes into the inventory.

Seep emissions will also remain constant in future year inventories.

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INITIAL AND BOUNDARY CONDITIONS

Initial Conditions

Initial conditions define the spatial distribution of chemical species concentrations

throughout the 3-dimensional modeling domain at the time at which the air quality

model simulation begins. There are two problems inherent in defining initial

conditions. The first is that chemical species concentrations are only measured at

discrete locations and, for some species, for discrete time periods. Therefore,

observed concentrations must be extrapolated to estimate concentrations

throughout the modeling domain. The second problem is that observed chemical

species concentrations may not represent chemical equilibrium, especially since

not all important chemical species are measured explicitly.

To minimize the importance of initial conditions on air quality model simulation

results, the simulation is frequently begun at some time interval before the period

of interest. Historically, this “spinup” time interval has ranged between 8 and 72

hours. For the SCOS97 episodes, the spinup period will begin at between 0000

PDT and 0500 PDT of the day before the first day of interest (the difference in the

begin time reflects the difference in time-base – GMT vs. local time – for some

meteorological models). This spinup period will allow a full diurnal cycle of

sunlight, prior to the period of interest, to enable the air quality model to reach

chemical equilibrium.

Initial conditions will be determined by interpolation/extrapolation of the chemical

species concentration measurements available from the SCOS97 field study

archive. For the large areas of the study domain in which there are few such

measurements, initial-conditions will be assigned “background” values based on

the minimum concentrations measured from monitoring sites where measurements

are available.

Boundary Concentrations

Boundary concentrations are chemical species concentrations on the study domain

boundaries and represent the concentrations for the air mass moving into the

domain. Unlike initial conditions which need to be defined only for the beginning

of the simulation, boundary conditions must be defined for each hour of an air

quality model simulation on the 2-dimensional, vertical planes on each of the

horizontal boundaries of the domain, and at the top of the modeling domain.

Ideally, modeling domain boundaries are placed so remotely that simulation results

are insensitive to boundary conditions. For the SCOS97 study domain, the

Eight-Hour Ozone Attainment Plan
SCOS Regional Modeling Protocol Document (DRAFT #3, 09/18/00) 31

influence of boundary conditions on the simulation results from an air quality

model is problematic. Beyond the northern SCOS97 boundary, emissions from

central California could have an impact on the domain. To the south, emissions

from Mexico could have an impact. The western boundary is over the Pacific

Ocean, where recirculation may be an issue. Boundary conditions will be

determined from measured chemical species concentrations where they are

available from the SCOS97 field study. Where measurements are not available,

background chemical species concentrations will be assigned based on the lowest

concentrations from sites where concentrations were measured. A part of the air

quality model evaluation process will be to assess the influence of boundary and

initial concentrations on

simulation results.

Eight-Hour Ozone Attainment Plan
SCOS Regional Modeling Protocol Document (DRAFT #3, 09/18/00) 32

MODEL PERFORMANCE EVALUATION

It is a well established tenet of the modeling community that for an air quality

modeling simulation to give reliable results, it must be capable of giving the right

answers for the right reasons. That is, not only must the model be capable of

reproducing observed ozone measurements with a reasonable level of accuracy, but

it must also pass a series of prescribed tests designed to ensure that the apparently

accurate results are not produced by a combination of compensating errors. As

discussed below, we propose to conduct several tests on the modeling simulations,

both at the surface and aloft–for precursor and secondary species in addition to

ozone–as part of the model performance process. The statistical tests will be

performed for the domain, by district, and for several subregions to ensure that the

domainwide statistics do not mask subregional problems. This information should

allow a determination that the model is working properly. Much of the following

information is taken from the ARB’s photochemical modeling guidance (ARB

1992).

Statistical and Graphical Analyses

The evaluation will include both graphical and statistical analyses. Graphical

analyses compare simulated pollutant concentrations with measured values. These

will include time series plots showing temporal variations, contour plots showing

spatial variations, scatter plots showing tendencies for over- or underestimation,

and residual plots showing the distribution of the differences between observed and

predicted concentrations. The statistical analyses will examine the accuracy of

peak estimates (both paired and unpaired in time and space), mean normalized

bias, mean absolute gross error, and mean absolute normalized gross error. The

statistical performance criteria outlined in the ARB’s guidance document for

Class B or better ozone performance will be used to guide the determination of

acceptable model performance. These statistical criteria will be used as a criterion

for acceptable model performance. However, other analyses (graphical, multispecies, aloft comparisons, and the diagnostic simulations) will also be used to

determine acceptable model performance, and ultimately a conclusion that the

model is working properly must be made considering all of the analyses.

• SUBREGIONAL PERFORMANCE

In addition to the domainwide statistical analyses, we propose to conduct

subregional analyses. The proposed subregions are San Diego County, the South

Coast Air Basin, the Mojave Desert, and the South Central Coast.

Eight-Hour Ozone Attainment Plan
SCOS Regional Modeling Protocol Document (DRAFT #3, 09/18/00) 33

Since the South Coast Air Basin is very large, we also propose to evaluate model

performance for four subregions within that area:

! Coastal Los Angeles and Orange counties;

! the central basin including downtown LA, southeast Los Angeles and inland

Orange county;

! the inland valley regions which include the San Gabriel Valley and the San

Fernando Valley; and

! the portions of Riverside and San Bernardino counties within the South Coast

Air Basin.

Since the modeling results may be used to support attainment demonstrations in

several districts, we propose to use the same statistical acceptance criteria for the

subregions as for the entire domain.

Multi-Species Evaluations

To be useful for planning or other purposes, an air quality model must be able to

replicate measured ozone concentrations with reasonable accuracy. However, it is

also important to compare estimated and measured concentrations of ozone

precursors and secondary species, to establish confidence that the chemistry

processes are being simulated properly. The important precursors are NO, NOx,

HONO, and organic gas species; important secondary species are HNO3 and PAN.

Organic gas concentrations will be lumped according to the scheme employed by

each model’s chemical mechanism. Comparisons will be made for each of the

estimated precursor species and lumped organic gas species, for each monitoring

location. In addition, comparisons will also be made for NOx, and total ROG.

These comparisons may reveal problems not associated with those for ozone

concentrations. Many of the precursor species have a secondary component as

well. Concentrations of primary pollutants tend to have higher gradients than do

secondary species. This makes it more difficult to assume that a measured

concentration of a primary pollutant represents a grid cell average. For these

reasons it is probably unreasonable to expect the same accuracy in replicating

precursor concentrations as for ozone concentrations. Thus we don’t recommend a

specific statistical error or bias criterion. These comparisons should be viewed as

qualitative, to uncover potential problems in precursor and secondary performance.

Aloft Comparisons

During the SCOS97 field study, concentrations of selected air pollutants were

measured above the ground using aircraft, balloons, and LIDAR. The primary

Eight-Hour Ozone Attainment Plan
SCOS Regional Modeling Protocol Document (DRAFT #3, 09/18/00) 34

component of these measurements was oxidant concentrations measured with

ozonesondes to a height of 5,000 m AGL. Ozonesondes were flown at 7 sites, at

6-hour intervals, for selected episode days. Also, 4 aircraft were flown up to 3

times per day and an ozone LIDAR was operated continuously on selected episode

days.

The performance of air quality model simulations above the ground will be

determined by comparing simulated oxidant and ozone concentrations with

measurements, for the same times and locations. Measured concentration profiles

will be averaged for the vertical layer increments corresponding to those of the air

quality model. Because of the vertical spacing required for the air quality models,

the vertical resolution of this comparison will be relatively poor. Therefore,

initially this comparison will be of a qualitative nature only.

In addition to measuring ozone, three of the aircraft measured oxides of nitrogen

and collected samples for later hydrocarbon analysis. Comparisons between these

precursor data and concentrations simulated using the air quality models will also

be made. However, there are relatively few samples and because an aircraft is not

in one grid cell for an hour, comparisons may not be consistent with modeled

concentrations. We will make the comparisons to see if any large discrepancies

exist between modeled and measured concentrations aloft.

Diagnostic Simulations

Several diagnostic, or investigative, simulations are proposed to further determine

the fidelity of the model results. These are anticipated to include the following:

• Zero emissions – all anthropogenic and biogenic emissions will be set to zero to

test the model’s sensitivity to emissions and to ensure that the base case

results are influenced appropriately by the emission inputs.

• Double anthropogenic emissions – all anthropogenic emissions will be doubled

to test the model's sensitivity to increased man-made emissions.

• Zero biogenics – biogenic emissions will be set to zero to test the model’s

sensitivity to biogenic emissions.

• Zero and clean air boundary and initial conditions – the initial (interior) and

boundary (at the top and sides of the modeling domain) conditions will be

set to zero and USEPA recommended clean air values to determine model

sensitivity to these inputs.

• Zero surface deposition – deposition will be turned off for all species to

examine the effects of dry deposition on ozone estimations.

• Reduced wind speeds – reducing the wind speeds by 50% is proposed to test the

model’s sensitivity to that parameter. However, the feasibility of doing so in

Eight-Hour Ozone Attainment Plan
SCOS Regional Modeling Protocol Document (DRAFT #3, 09/18/00) 35

the event that a dynamically consistent, prognostic model is used, has not yet

been investigated.

• Reduced mixing heights – reducing mixing heights by 50% is proposed to test

the model’s sensitivity to that parameter. However, the feasibility of doing

so in the event that a dynamically consistent, prognostic model is used, has

not yet been investigated.

• Alternative meteorological inputs – if an alternate procedure for preparing

meteorological inputs provides acceptable fields, these will be simulated to

test the model’s response to similar but different fields. For example, if

prognostic outputs are used as the primary meteorological fields, but

diagnostic fields are available and are judged technically credible, they will

be used as alternative inputs.

Eight-Hour Ozone Attainment Plan
SCOS Regional Modeling Protocol Document (DRAFT #3, 09/18/00) 36

USE OF THE MODELING RESULTS

It is anticipated that the model results will be used for the following planning

activities: carrying capacity estimation, attainment demonstration, and transport

assessment. Other uses are dependent on the regulatory needs of the stakeholders,

and will be coordinated via the agency stakeholder meetings with local, state, and

Federal agency participation. All planning uses of the model results are contingent

upon acceptable base case model performance for the episodes simulated. That is,

only episodes which meet the model performance acceptance criteria will be used.

Carrying Capacity Estimation

A traditional use of models for planning has been the estimation of carrying

capacities for ozone precursors. This is typically achieved by exercising the model

with a series of across-the-board precursor emission reductions from the future

year baseline, from which an ozone isopleth (“EKMA”) diagram is constructed.

The metric used for the isopleth diagram can be one of several, such as peak

1-hour or 8-hour ozone concentrations within the modeling domain (or subregion),

number of grid cells above the standard, or one of many population exposure

metrics. For the SCOS97 region, we propose to construct isopleth diagrams by

episode for at least the following air quality metrics:

• Peak 8-hour ozone concentration for the domain, adjusted using USEPA’s

relative reduction factor (RRF) approach.

• Peak 1-hour ozone concentration for the domain, adjusted using RRFs.

• Air basin-specific peak 8-hour ozone concentration (adjusted using RRFs) for

those of the following air basins which experienced 8-hour ozone violations

during a given episode: the South Central Coast Air Basin; San Diego County;

the SCAQMD; the Mojave Desert (including Antelope Valley); and Imperial

County.

• Same as the preceding bullet but for RRF-adjusted peak 1-hour ozone

concentrations.

Ozone design values for RRF application will be calculated based on monitoring

from 1997 through 1999 for both the 1-hour and 8-hour standards. The resulting

isopleth diagrams will be shared with the stakeholder agencies, from which

additional simulations can be identified and coordinated.

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SCOS Regional Modeling Protocol Document (DRAFT #3, 09/18/00) 37

Attainment Demonstration

As required by the USEPA in their draft 8-hour ozone guidance (USEPA 1998b),

we propose to use relative reduction factors (RRFs) as part of the attainment

demonstration process for the 8-hour ozone standard, assuming that satisfactory

base year model performance is established. The RRF approach incorporates

design period monitoring data directly into the attainment test along with the ratio

of future to current year model estimations. This allows the model to be used in a

relative, rather than absolute, sense to reduce uncertainty in the predictions.

We will also consider the use of an RRF type adjustment factor for the 1-hour

standard. If properly applied, we believe that the use of RRFs can provide better

estimates of the emission reductions needed for attainment. This is because they

are capable of addressing two problems in model applications that tend to result in

underestimation of emission reductions needed. The first problem is that modeled

episodes usually have ozone concentrations lower than the design value. The

second problem is that simulation results have historically exhibited a tendency

towards underestimation of observed concentrations. By utilizing monitored data

along with model estimations, RRFs address both problems.

As shown in the following table, it will be necessary to simulate multiple future

attainment years to fully address planning needs in the region. Because of the

staggered nature of the attainment years, it will be necessary to coordinate future

year inventories within the region to facilitate the required simulations.

Probable Ozone Attainment Years in the Region

Area 1-Hour National Standard 8-Hour National Standard

Mojave Desert

San Diego

Santa Barbara

South Coast

Ventura

2007

1999

1999

2010*

2005

↓

↓

2005-2010? for all areas**

↑

↑

* The SCAQMD and the ARB are jointly preparing a year 2000 AQMP that will address the

1-hour ozone standard for the SCAQMD and the Mojave Desert. That process is on a separate

schedule, however much of the work on and products from that process will be of use to the

SCOS97 regional modeling.

** Appropriate attainment dates to be determined during the SIP development process.

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SCOS Regional Modeling Protocol Document (DRAFT #3, 09/18/00) 38

Transport Assessment

Transport within the region is of obvious importance to the agency stakeholders. It

is anticipated that, if acceptable model performance is established, the regional

modeling may be useful to address some transport issues that are of concern to the

local agencies. This assumes that the episodes simulated manifest the type(s) of

meteorology conducive to transport between couples. We propose to work with

the stakeholder agencies to identify and prioritize potential transport scenarios and

simulations of interest within the region. This may involve simulations where

anthropogenic emissions in one or more areas are turned off or reduced, or may

take advantage of some of the newer models’ (e.g., CAMx) ability to conduct

source apportionment. However, modeling in support of the attainment

demonstrations will remain our highest priority.

Eight-Hour Ozone Attainment Plan
SCOS Regional Modeling Protocol Document (DRAFT #3, 09/18/00) 39

TECHNICAL OVERSIGHT

As with previous modeling efforts by the ARB, it is intended that the modeling

process be an open one. That is, the involvement of all interested stakeholders and

other technical experts is welcome throughout the process. Such involvement will

allow comments and suggestions to be accommodated during the process, rather

than foster disagreement at the end.

A SCOS97 Emission Inventory Working Group has already been established, and

has met several times to discuss inventory-related issues and coordinate inventory

preparation activities. The ARB has also hosted a series of ongoing agency

stakeholder modeling meetings in Southern California to discuss the various

aspects of the inventory, modeling, and planning processes. A meteorological

working group has also been established to review the preparation of

meteorological inputs. Members for other technical working groups will be

solicited, and other peer review mechanisms considered, based on stakeholder

input. As progress is made and products are available, interim results will be

shared with the agency stakeholders in an agreed upon format and with the

interested public at appropriate times and locations.

Eight-Hour Ozone Attainment Plan
SCOS Regional Modeling Protocol Document (DRAFT #3, 09/18/00) 40

SCHEDULE AND DELIVERABLES

Schedule

Much of the work to prepare meteorological inputs, initial and boundary

conditions, and to test and evaluate air quality models for the SCOS97 domain will

be carried out as part of a joint effort by the staffs of the ARB and the SCAQMD

to prepare that district’s year 2000 AQMP. In addition, base year and future year

baseline emission inventories will be prepared as part of the joint effort. The

current schedule calls for that technical work to be completed by mid 2000.

The following table provides some preliminary milestones for the modeling

process. Additional milestones will be developed in coordination with the agency

stakeholders.

Tentative Milestones for 1- and 8-Hour SCOS97 Modeling

Task

• Completion of technical work in support of

SCAQMD year 2000 AQMP

• Development of regional and air basin-specific

carrying capacities.

Due Date

Mid-2000

Mid-2001

Deliverables

As discussed previously, all interim products and summaries will be provided to

the individual technical working groups (emission inventory, meteorology, air

quality, etc.). Comments and suggestions will be solicited from the working

groups throughout the entire process.

In addition to the interim products, specific deliverables will be shared with the

agency stakeholders via the regularly scheduled meetings of the local, state, and

Federal agencies, and at public meetings convened at strategic times. These

deliverables will include at least the following:

• Carrying capacity estimations. These are intended to provide an initial

assessment of the emission targets for each region. Due to the large number of

air basins included within the SCOS97 domain, and the potential for different

Eight-Hour Ozone Attainment Plan
SCOS Regional Modeling Protocol Document (DRAFT #3, 09/18/00) 41

attainment dates, the methodology for conducting these simulations will need

to be worked out with the district stakeholders. However, we have proposed

an initial methodology in the “USE OF THE MODELING RESULTS” section.

• The results of any 1-hour and 8-hour ozone attainment demonstration

simulations carried out. As indicated above, the methodology for conducting

these simulations will need to be worked out with the district stakeholders.

Control measures for each district will need to be supplied by district staff.

• The results from any agreed upon transport assessments. The ARB will work

with the local agencies via the regularly scheduled agency stakeholder

meetings to identify appropriate and necessary transport simulations.

Eight-Hour Ozone Attainment Plan
SCOS Regional Modeling Protocol Document (DRAFT #3, 09/18/00) 42

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Eight-Hour Ozone Attainment Plan
Listing of the SCOS97 stations with their locations and mnemonics.

Eight-Hour Ozone Attainment Plan
ID Description

LatDeg Lat- Min Lat- Sec Lon- Deg Lon- Min Lo

Se

29PL MDAQMD TWENTY NINE PALMS-6078 ADOBE RD 34 8 31 116 3 ACTN ACTION 34 26 45 118 12 AGRN ARROYO GRANDE 35 11 31 120 25 ALPM Alpine 32 51 53 116 48 ALPN SDAQMD*ALPINE-2300 VICTORIA DR 32 49 58 116 45 ANAH SCAQMD*ANAHIEM-1610 S HARBOR BLVD 33 49 11 117 54 ANZA ANZA 33 33 18 116 40 APRT USFS ANGELES PORTABLE 34 0 0 117 0 ARED CIMIS ARVIN-EDISON 35 12 22 118 46 ARGR XONTEC ARROYO GRANDE-RALCOA WAY 35 2 38 120 34 ARVN CARB *ARVIN-20401 BEAR MTN BLVD 35 12 28 118 47 ATAS SLOCO *ATASCADERO-6005 LEWIS AVE 35 29 27 120 40 AZSA SCAQMD*AZUSA-803 N LOREN AVE 34 8 9 117 55 AZSM 34 9 37 117 54 BANH SCAQMD*BANNING-135 N ALLESANDRO 33 55 40 116 52 BANN SCAQMD*BANNING-135 N ALLESANDRO 33 55 40 116 52 BARS MDAQMD*BARSTOW-200 E BUENA VISTA 34 53 41 117 1 BEAR BLM BEAR PEAK 35 53 3 118 3 BELL BELL CANYON 33 32 30 117 35 BKGS SJVUCD*BAKERSFIELD-1138 GOLDEN STATE 35 23 5 119 0 BKWC CIMIS BLACKWELLS CORNER 35 38 59 119 57 BLFC CARB *BAKERSFIELD-5558 CALIFORNIA ST 35 21 21 119 2 BLHT CIMIS BLYTHE NE 33 33 24 114 39 BLKM Black MounSDCAPCD 32 58 54 117 6 BRBK SCAQMD*BURBANK-228 W PALM AVE 34 10 33 118 18 BRMT USFS BRANCH MOUNTAIN 35 11 20 120 5 BRST CIMIS BARSTOW NE 34 53 3 116 59 BRWN Brown FielNOAA 32 34 20 116 58 BSHP CIMIS BISHOP 37 21 29 118 24 BURN BLM BURNS CANYON 34 12 30 116 37 

Eight-Hour Ozone Attainment Plan
ID Description

LatDeg Lat- Min Lat- Sec Lon- Deg Lon- Min Lo

Se

BY23 Buoy 46023 34 42 50 120 58 BY45 Buoy 46045 34 50 12 118 27 BY54 Buoy 46054 34 16 8 120 26 CAJB Cajon Pass (AV) 34 22 31 117 26 CALB Calabasas (AV) 34 8 52 118 36 CALE CARB *CALEXICO-CALEXICO HS ETHEL ST 32 40 33 115 28 CAMB CIMIS CALIPATRIA/MULBERRY 33 2 37 115 24 CARL Carlsbad NOAA 33 8 22 117 16 CARR BLM CARRIZO 35 5 47 119 46 CASE CASE SPRINGS 33 26 43 117 25 CATA Catalina AP (AV) 33 26 30 118 29 CATH CIMIS CATHEDRAL CITY 33 50 33 116 28 CATI Catalina Isl (AV) 33 24 17 118 24 CATM Santa CataNOAA 33 26 44 118 28 CBC USN PORT HUENEME CBC 34 8 47 119 12 CHES NPS CHEESEBORO 34 11 5 118 43 CHIL USFS CHILAO 34 20 0 118 2 CHVT SDAQMD*CHULA VISTA-80 E "J" ST 32 37 22 117 3 CLEM San ClemenSDCAPCD 32 54 55 118 29 CLRM CIMIS CLAREMONT 34 7 48 117 41 CLXC ICAPCD*CALEXICO-900 GRANT ST 32 40 26 115 30 CLXE Calexico CARB 32 49 29 115 29 CMFS USFS CAMERON FIRE STATION 32 43 17 116 27 CMMV SCAQMD*COSTA MESA-2850 MESA VERDE DR 33 40 29 117 55 CMP9 CAMP 9 34 21 42 118 25 CMPT CMP TARGET RANGE 33 22 20 117 21 CONV USFS CONVERSE 34 11 1 116 55 CPGB CHVRON*CARPINTERIA-GOBERNADOR RD 34 24 10 119 27 CRZW 34 3 37 119 55 CUYA CIMIS CUYAMA 34 55 54 119 36 DELO BLM DELONAGHA 35 34 12 118 37 DEVO DEVORE 34 13 16 117 24 DMMC SDAQMD*DEL MAR-MIRACOSTA COLLEGE 32 57 10 117 15 ECAJ SDAQMD*EL CAJON-1155 REDWOOD AVE 32 47 27 116 56 

Eight-Hour Ozone Attainment Plan
ID Description

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ECSP SBAPCD*EL CAPITAN STATE PARK 34 27 39 120 1 EDSN CARB *EDISON-JOHNSON FARM 35 20 45 118 51 ELCR USFS EL CARISO 33 39 6 117 24 ELDO CIMIS EL DORADO 33 47 50 118 5 ELRO VCAPCD*EL RIO-RIO MESA SCHOOL 34 15 53 119 8 ELTR SCAQMD*EL TORO-23022 EL TORO RD 33 37 37 117 41 EMAM El Monte CARB 34 4 12 118 1 EMMA VCAPCD*EMMA WOOD STATE BEACH 34 17 23 119 19 ESCD CIMIS ESCONDIDO 33 5 24 116 58 ESCO SDAQMD*ESCONDIDO-600 E. VALLEY PKWY 33 7 40 117 4 FAMS CIMIS FAMOSO 35 36 14 119 12 FAWN USFS FAWNSKIN 34 15 58 116 53 FISH BLM FISH CREEK MOUNTAI 32 59 0 116 3 FONT SCAQMD*FONTANA-14360 ARROW BLVD 34 6 0 117 30 FRBH CIMIS FIREBAUGH/TELLES 36 51 4 120 35 FSPR FOUNTAIN SPRINGS 35 53 32 118 54 FSU CIMIS FRESNO STATE 36 49 15 119 44 FVML BLM FIVE MILE 35 52 18 117 55 FVPT CIMIS FIVEPOINTS/WSFS USDA 36 20 11 120 6 GAFH CIMIS GOLETA FOOTHILLS 34 28 18 119 52 GAIL 34 7 33 119 24 GAVE CHVRON*GAVIOTA EAST-N OF CHEVRON PLAN 34 28 40 120 12 GAVW CHVRON*GAVIOTA WEST-NW OF CHEVRON PLA 34 28 40 120 12 GCTY SLOCO *GROVER CITY-9 LE SAGE DR 35 7 30 120 37 GLDR SCAQMD*GLENDORA-840 LAUREL 34 8 38 117 51 GLEL CIMIS GLENDALE 34 12 0 118 13 GLWF SBAPCD*GOLETA-380 W FAIRVIEW AVE 34 26 41 119 49 GOLE SBAPCD GOLETA-380 N FAIRVIEW 34 26 41 119 47 GRAN BLM GRANITE MOUNTAIN 34 32 8 117 1 GTCB TEXACO*NOJOQUI PASS-GTC B HWY 101 34 31 40 120 11 GTCC TEXACO*GAVIOTA-GTC C 1 MI E OF PLANT 34 28 29 120 11 GUAD CIMIS GUADALUPE 34 57 42 120 32 HAWH SCAQMD*HAWTHORNE-5234 W. 120TH ST 33 55 51 118 22 HESP MDAQMD*HESPERIA-17288 OLIVE ST 34 25 4 117 17 

Eight-Hour Ozone Attainment Plan
ID Description

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HOND Platform Hondo 34 24 0 120 6 HORS BLM HORSE THIEF SPRING 35 46 14 115 54 HUEN Oxnard NOAA 34 9 54 119 13 INDO SCAQMD*INDIO-46-990 JACKSON ST 33 42 32 116 12 INWC BLM INDIAN WELLS CANYON 35 41 6 117 53 IREN 34 36 40 120 43 IRVI CIMIS IRVINE 33 41 19 117 43 JAWB BLM JAWBONE 35 17 40 118 13 JOSH NPS JOSHUA TREE NATIONAL MONUMENT 34 4 15 116 23 JPFT JUNIPER FLAT 33 46 41 117 5 JULI JULIAN 33 4 33 116 35 KEEN USFS KEENWILD 33 42 47 116 42 KEST CIMIS KESTERSON 37 13 57 120 52 KETT CIMIS KETTLEMAN 35 52 8 119 53 LAGP LAGUNA PEAK 34 6 31 119 3 LANM SCAQMD*LOS ANGELES-1630 N MAIN ST 34 4 1 118 14 LAPZ LA PANZA 35 22 52 120 11 LELS SCAQMD*LAKE ELSINORE-506 W FLINT ST 33 40 29 117 20 LFC1 EXXON *CAPITAN-LFC #1 LAS FLORES CNYN 34 29 23 120 2 LFC2 EXXON *CAPITAN-LFC #2 LAS FLORES CNYN 34 28 44 120 1 LFC3 EXXON *CAPITAN-LFC #3 LAS FLORES CNYN 34 28 8 120 2 LFC4 EXXON *CAPITAN-LFC #4 LAS FLORES CNYN 34 28 51 120 2 LGRE SCAQMD*CRESTLINE-LAKE GREGORY-LAKE DR 34 14 38 117 16 LHAB SCAQMD*LA HABRA-621 W. LAMBERT 33 55 33 117 57 LIND CIMIS LINDCOVE 36 21 26 119 3 LODI CIMIS LODI 38 6 34 121 20 LOSB CIMIS LOS BANOS 37 5 30 120 45 LOSP UNOCAL*LOS PADRES NF-PARADISE RD 34 32 27 119 47 LOST NPS LOST HORSE 34 1 4 116 11 LPHP UNOCAL*LOMPOC-HS&P FACILITY 500 M SW 34 43 8 120 25 LPHS UNOCAL*LOMPOC-HS&P FACILITY 500 M SW 34 43 33 120 25 LPSH SBAPCD*LOMPOC-128 S 'H' ST 34 38 16 120 27 LRLM BLM LAURAL MOUNTAIN 35 28 42 117 41 LSF LSF LAS FLORES 33 17 20 117 26 

Eight-Hour Ozone Attainment Plan
ID Description

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LTAB LAS TABLAS 35 39 20 120 55 LYNW SCAQMD*LYNWOOD-11220 LONG BEACH BLVD 33 55 44 118 12 MANT CIMIS MANTECA 37 50 5 121 13 MBLD Azusa CARB 34 14 21 117 37 MELO CIMIS MELOLAND 32 48 24 115 26 MEXA Mexicali CARB 32 39 31 115 25 MEXI Mexicali CARB 32 37 10 115 23 MEXT Mexicali CARB 32 34 13 115 20 MEXU Mexicali CARB 32 37 45 115 26 MID BLM MID HILLS 35 9 58 115 24 MILL USFS MILL CREEK 34 23 0 118 4 MOBY SLOCO *MORRO BAY-MORRO BAY BL & KERNR 35 22 4 120 47 MODE CIMIS MODESTO 37 38 10 121 11 MOJA BLM MOJAVE RIVER SINK 35 3 30 116 5 MOJP CARB *MOJAVE-923 POOLE ST 35 3 3 118 8 MONT USFS MONTECITO 34 27 6 119 38 MRCP SJVUCD*SCHOOL-755 STANISLAUS ST, MARI 35 3 14 119 24 MTLG USFS MT LAGUNA 32 52 47 116 25 NAFB Norton AFBCARB 34 9 12 117 15 NIPO UNOCAL NIPOMO-1300 GUADALUPE RD 35 1 19 120 34 NLGB SCAQMD*LONG BEACH-3648 N LONG BEACH 33 49 26 118 11 NXP NWS TWENTYNINE PALMS 34 7 48 115 56 OAKG USFS OAK GROVE 33 23 36 116 47 OASS CIMIS OASIS 33 31 32 116 9 OCEA SDAQMD*OCEANSIDE-1701 MISSION AVE 33 12 10 117 22 OCSD CIMIS OCEANSIDE 33 15 21 117 19 ODOR CHVRON*GAVIOTA-ODOR WEST-S OF PLANT 34 28 15 120 13 OJAI VCAPCD OJAI-1768 MARICOPA HIWY 34 26 49 119 16 OLDL CARB *OILDALE-3311 MANOR ST 35 26 20 119 0 OPAL BLM OPAL MOUNTAIN 35 9 15 117 10 OTAY SDAQMD*OTAY-1100 PASEO INTERNATIONAL 32 35 2 116 56 PALM SCAQMD*PALM SPRINGS-FS 590 RACQUET CL 33 51 17 116 32 PANO CIMIS PANOCHE 36 53 25 120 43 PDSW SCAQMD*PASADENA-752 S. WILSON AVE 34 5 2 118 6 

Eight-Hour Ozone Attainment Plan
ID Description

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PEND Camp Del MSDCAPCD 33 13 2 117 23 PERR SCAQMD*PERRIS-237 .5 N "D" ST 33 47 27 117 14 PFLD PARKFIELD 35 53 56 120 25 PHEL MDAQMD*PHELAN-BEEKLEY & PHELAN RDS 34 25 33 117 33 PICO SCAQMD*PICO RIVERA-3713 SAN GABRIEL 34 0 46 118 3 PIRU CIMIS PIRU 34 22 30 118 47 PLVD CIMIS PALO VERDE 33 23 15 114 43 POMA SCAQMD*POMONA-924 N. GAREY AVE 34 4 1 117 45 POMO CIMIS POMONA 34 3 30 117 48 POTR POTRERO 32 36 22 116 36 PRLR CIMIS PARLIER 36 35 52 119 30 PRTG VCAPCD*PIRU-2SW, 2815 TELEGRAPH RD 34 23 56 118 49 PSRB CARB *PASO ROBLES-235 SANTA FE AVE 35 37 55 120 41 PTCL CHVRON*POINT CONCEPTION LIGHTHOUSE 34 27 7 120 27 PTHU CIMIS PORT HUENEME 34 10 24 119 12 PVSP Palos Verdes (AV) 33 44 46 118 20 RAMO CIMIS RAMONA 33 2 58 116 56 RANC RANCHITA 33 12 44 116 30 RDLD SCAQMD*REDLANDS-500 N. DEARBORN 34 3 35 117 9 REDM Fallbrook SDCAPCD 33 24 2 117 11 ROSE USFS ROSE VALLEY 34 32 35 119 11 ROSW 34 0 31 120 14 RSDA SCAQMD*RESEDA-18330 GAULT ST 34 11 56 118 31 SANB SCAQMD*SAN BERNARDINO-24302 4TH ST 34 6 28 117 16 SAND CIMIS SAN DIEGO 32 43 59 117 8 SBAR NPS SANTA BARBARA 33 29 0 119 2 SBWC CARB *SANTA BARBARA-3 W. CARRILLO ST 34 25 15 119 42 SCIS NPS SANTA CRUZ ISLAND 33 59 45 119 43 SCLA Santa Clarita -- Sodar site 34 23 9 118 31 SCLH San Clemente Island 32 52 33 118 25 SCLM San ClemenNOAA 33 1 7 118 35 SCLR Santa ClarSCAQMD 34 23 16 118 32 SD12 SDAQMD*SAN DIEGO-330A 12TH AVE 32 42 32 117 9 SDOV SDAQMD*SAN DIEGO-5555 OVERLAND AVE 32 49 40 117 7 

Eight-Hour Ozone Attainment Plan
ID Description

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SELY CIMIS SEELEY 32 45 34 115 43 SFDM SANTA FE DAM 34 7 15 117 56 SGUS SAUGUS 34 25 30 118 31 SHAF CIMIS SHAFTER/USDA 35 31 59 119 16 SHFT CARB *SHAFTER-548 WALKER ST 35 30 14 119 16 SLOM CARB *SAN LUIS OBISPO-1160 MARSH ST 35 17 2 120 39 SLOP CIMIS SAN LUIS OBISPO 35 18 22 120 39 SLTE CIMIS SALTON SEA EAST 33 13 12 115 34 SLTW CIMIS SALTON SEA WEST 33 19 38 115 57 SMI San Miguel Island 34 1 59 119 21 SMPK Deer SprinSDCAPCD 33 11 6 117 7 SMSB CARB *SANTA MARIA-500 S BROADWAY B69 34 56 52 120 26 SNBA CIMIS SANTA BARBARA 34 26 16 119 44 SNBO SCAQMD*SAN BERNARDINO-ARB 34 5 56 117 40 SNI SAN NICOLOS ISLAND 33 14 0 119 27 SNTM CIMIS SANTA MARIA 34 57 16 120 23 SNTY CIMIS SANTA YNEZ 34 34 59 120 4 SOLM La Jolla SDCAPCD 32 50 27 117 15 SQSP BLM SQUAW SPRINGS 35 22 12 117 34 SRIS NPS SANTA ROSA ISLAND 33 58 40 120 4 SRPL SANTA ROSA PLATEAU 33 31 43 117 13 STAM CIMIS SANTA MONICA 34 2 28 118 28 STRA CIMIS STRATFORD 36 9 27 119 51 SVAL VCAPCD*SIMI VALLEY-5400 COCHRAN ST 34 16 40 118 41 SVLM Simi ValleVCAPCD 34 17 27 118 47 SYAP SBAPCD*SANTA YNEZ-AIRPORT RD 34 36 10 120 4 TANB USFS TANBARK 34 10 0 117 46 TEME CIMIS TEMECULA 33 29 25 117 13 THER CIMIS THERMAL 33 38 47 116 14 THOS CARB *OAK VIEW-5500 CASITAS PASS RD 34 23 13 119 24 TILM Tijuana CARB 32 29 52 116 58 TIPL Tijuana CARB 32 30 50 117 6 TIRP Tijuana CARB 32 21 12 117 3 TITT Tijuana CARB 32 31 30 116 59 

Eight-Hour Ozone Attainment Plan
ID Description

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TME2 CIMIS TEMECULA-EAST II 33 33 24 117 1 TOMP VCAPCD*THOUSAND OAKS-9 2323 MOORPARK 34 12 35 118 52 TRNA MDAQMD*TRONA-83732 TRONA ROAD 35 46 29 117 22 TUST Tustin NOAA 33 42 25 117 50 UCR CIMIS U.C. RIVERSIDE 33 57 54 117 20 UCSB EXXON *UCSB WEST CAMPUS-ARCO TANK, IS 34 24 53 119 52 UHL UHL 35 48 0 118 36 USCZ Los AngeleNOAA 34 1 10 118 17 VALA SCAQMD*W LOS ANGELES-VA HOSPITAL 34 3 3 118 27 VBPP VBGAFB*VANDENBERG AFB-STS POWER PLANT 34 35 45 120 37 VCEN SDAPCD VALLEY CENTER 33 13 57 117 1 VDMR CHVRON*GAVIOTA-ODOR EAST 34 28 19 120 10 VICT VICTORVILLE 34 30 15 117 19 VLYC VALLEY CENTER 33 13 34 116 59 VNUY Van Nuys 34 12 57 118 29 VSLA CIMIS VISALIA/ICI AMERICAS 36 18 3 119 13 VTRV CIMIS VICTORVILLE 34 28 42 117 15 WALK BLM WALKER PASS 35 39 53 118 3 WARM USFS WARM SPRINGS 34 35 0 118 33 WSPR WARNER SPRINGS 33 19 20 116 41 WTLD CIMIS WESTLANDS 36 38 0 120 22 YCAV YUCCA VALLEY 34 7 24 116 24 APE +Alpine Profiler 32 51 36 116 48 AZS Azusa Profiler 34 9 36 117 54 BFD +Brown Field Profiler 32 34 12 116 59 BTW +Barstow Profiler 34 55 12 117 18 CBD +Carlsbad Profiler 33 8 24 117 16 EAF Edwards AFB Profiler 34 17 60 116 10 ECO +El Centro Profiler 32 49 48 115 34 EMT +El Monte Profiler EMT 34 5 24 118 1 GLA +Goleta Profiler 34 25 48 119 50 HPA +Hesperia Profiler 34 23 24 117 24 LAS +Las Alamitos,CA Profiler 33 47 24 118 3 LAX +Los Angeles International Profiler 33 56 24 118 26 

Eight-Hour Ozone Attainment Plan
ID Description

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NTN +Norton Air Force Base Profiler 34 5 24 117 15 ONT +Ontario Profiler 34 3 36 117 34 PDE +Palmdale Profiler 34 36 36 118 5 PHE +Port Hueneme Profiler 34 10 12 119 13 PLM +Point Loma Profiler 32 42 0 117 15 RSD +Riverside Profiler 33 55 12 117 18 SCA Santa Clarita Profiler 34 25 12 118 31 SCE +San Clemente Island Profiler 33 1 12 118 35 SCL +Santa Catalina Island Profiler 33 27 0 118 28 SMIP +Simi Valley Profiler 34 17 24 118 48 TCL +Temecula Profiler 33 30 0 117 9 TML +Thermal Profiler 33 38 24 116 9 TTN +Tustin Marine Base Profiler 33 42 36 117 50 29P 29 Palms Profiler 34 18 36 116 15 USC +USC Profiler 34 1 12 118 16 VAF +Vandenberg Air Force Base Profiler 34 46 12 120 31 VLC +Valley Center Profiler 33 15 36 117 2 VNS +Van Nuys Profiler 34 13 12 118 29 

Eight-Hour Ozone Attainment Plan