i 

Commonwealth of Pennsylvania 

Department of Environmental Protection

Final Air-Quality Modeling Protocol 

For the Annual PM2.5 NAAQS 

Philadelphia-Wilmington, PA-NJ-DE 

Annual PM2.5 Nonattainment Area 

October 2007 

Bureau of Air Quality 

Pennsylvania Department of Environmental Protection 

P.O. Box 8468 

Harrisburg, PA 17105-8468 

717-787-9495 

www.dep.state.pa.us 
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Table of Contents 

1.0 Overview of Philadelphia-Wilmington Annual PM2.5 Nonattainment Modeling 

Demonstration..................................................................................................................... 1 

1.1 Background and Objectives ..................................................................................... 1 

1.2 Philadelphia-Wilmington Annual PM2.5 Nonattainment Area ................................ 2 

1.3 Philadelphia-Wilmington Data Analysis Summary................................................. 4 

1.4 Technical Committees ............................................................................................. 5 

1.5 Participating Organizations...................................................................................... 6 

1.6 Schedule for Completion ......................................................................................... 6 

2.0 Model and Modeling Inputs......................................................................................... 6 

2.1 Selection of Air Quality, Meteorological and Other Model Inputs ......................... 6 

2.2 Modeling Domain .................................................................................................... 7 

2.3 Horizontal and Vertical Grid Resolution ................................................................. 7 

2.4 Model Initial and Boundary Conditions .................................................................. 8 

2.5 Near-Scale Modeling ............................................................................................... 8 

2.6 Episode Selection..................................................................................................... 9 

2.7 Meteorological Model.............................................................................................. 9 

2.8 Emission Inputs...................................................................................................... 10 

2.9 Area Examined in the Attainment Demonstration................................................. 10 

2.10 Quality Assurance................................................................................................ 11 

3.0 Model Performance Evaluation ................................................................................. 12 

3.1 Ambient Data Base ................................................................................................ 12 

3.2 Evaluation Procedures ........................................................................................... 13 

4.0 Attainment Demonstration and other Supplemental Analyses .................................. 13 

4.1 Model Attainment Test .......................................................................................... 13 

4.2 Unmonitored Area Analysis .................................................................................. 14 

4.3 Additional Analyses............................................................................................... 15 

5.0 Procedural Requirements........................................................................................... 15 

5.1 Reporting................................................................................................................ 16 

5.2 Data Archive and Delivery of Modeling Files....................................................... 16 

6.0 References.................................................................................................................. 16 

Table of Figures

Figure 1-1 Philadelphia-Wilmington Annual PM2.5 Nonattainment Area......................... 3 

Figure 1-2 Annual Design Values: Philadelphia-Wilmington annual PM2.5

Nonattainment Area.................................................................................................... 4 

Figure 2-1 OTC Modeling Study Domain......................................................................... 7 

Table of Tables

Table 1-1 Historic Design Values: Philadelphia-Wilmington annual PM2.5

Nonattainment Area.................................................................................................... 4 

Table 1-2 Summary of PM2.5 WOE Guidelines (from the U.S. EPA Guidance) ............ 15 
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1.0 Overview of Philadelphia-Wilmington Annual PM2.5 Nonattainment Modeling 

Demonstration 

This section provides background information and describes the basic structure to the 

PM2.5 demonstration that the Pennsylvania Department of Environmental Protection (PA 

DEP) will undertake. Final modeling guidelines for PM2.5 were issued on April 16, 2007 

(posted on the U.S. EPA’s Support Center for Regulatory Air Modes, SCRAM). This 

modeling protocol follows the structure outlined in section 12.2 of the U.S. EPA’s 

Guidance on the Use of Models and Other Analyses for Demonstrating Attainment of Air 

Quality Goals for Ozone, PM2.5, and Regional Haze. 

1.1 Background and Objectives 

Background information on PM2.5 included in this section was taken from the U.S. EPA’s 

website (www.epa.gov/pmdesignations/). This includes basic information on PM2.5

components and their health affects. 

Particle pollution is a mixture of microscopic solids and liquid droplets suspended in air. 

This pollution, also known as particulate matter, is made up of a number of components, 

including acids (such as nitrates and sulfates), organic chemicals, metals, soil or dust 

particles, and allergens (such as fragments of pollen or mold spores). 

Fine particle pollution or PM2.5 describes particulate matter that is less than or equal to 

2.5 μm in diameter, approximately 1/30th the diameter of a human hair. 

Fine particle pollution can be emitted directly or formed secondarily in the atmosphere. 

Examples of some of the primary forms of secondary pollutants include: 

Sulfates: These are formed from sulfur dioxide emissions from power plants and 

industrial facilities. 

Nitrates: These are formed from emissions of nitrogen oxides from power plants, 

automobiles, and other combustion sources. 

The chemical composition of particles depends on location, time of year, and weather. 

Health studies have shown a significant association between exposure to fine particles 

and premature death from heart or lung disease. Fine particles can aggravate heart and 

lung diseases and have been linked to effects such as: cardiovascular symptoms; cardiac 

arrhythmias; heart attacks; respiratory symptoms; asthma attacks; and bronchitis. These 

effects can result in increased hospital admissions, emergency room visits, absences from 

school or work, and restricted activity days. Individuals that may be particularly sensitive 

to fine particle exposure include people with heart or lung disease, older adults, and 

children. 
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The U.S. EPA issued the fine particle standards in 1997 after evaluating hundreds of 

health studies and conducting an extensive peer review process. The annual standard is a 

level of 15.0 micrograms per cubic meter (μg/m3), based on the 3-year average of annual 

mean PM2.5 concentrations. The U.S. EPA established a twenty-four hour standard of 65 

micrograms per cubic meter (μg/m3

), determined by the 3-year average of the annual 98th 

percentile concentrations. In 2006 the U.S. EPA lowered the twenty-four hour PM2.5

standard to 35 μg/m3

. Because the nonattainment designations for new twenty-four hour 

PM2.5 standard are not yet in place, the Commonwealth’s PM2.5 modeling analyses will 

instead use the1997 twenty-four hour standard (65 μg/m3

). Final PM2.5 SIPs are due in 

April of 2008. 

In April 2003, the U.S. EPA issued a memorandum outlining the schedule for designating 

areas under the PM2.5 standard and related guidance on nine factors to consider in 

identifying nonattainment areas. The Clean Air Act provides for states and tribes to 

submit designation recommendations to the U.S. EPA, and it requires the U.S. EPA to 

provide time for consultation in cases where the Administrator plans to promulgate a 

designation that modifies the state or tribal recommendation. On December 17, 2004 The 

U.S. EPA published its air quality designations and classifications for the fine particles 

(PM2.5) national ambient air quality standards (NAAQS). These designations became 

effective on April 5, 2005.

The objective of this protocol is to outline the methods and procedures that will be used 

to support the modeling demonstration. The Department will take the lead in developing 

emission control strategies to demonstrate the Philadelphia-Wilmington annual PM2.5

nonattainment area will reach attainment by the designated attainment date, April 2010 

(five years from the final designations). 

1.2 Philadelphia-Wilmington Annual PM2.5 Nonattainment Area 

The Philadelphia-Wilmington annual PM2.5 nonattainment area is a three-state 

nonattainment area including the five-county Philadelphia area (Pennsylvania), one 

county in Delaware and three counties in the state of New Jersey. Figure 1-1 graphically 

depicts all of the annual PM2.5 nonattainment areas within Pennsylvania. 

The Philadelphia-Wilmington nonattainment area currently violates the U.S. EPA’s 

health-based annual PM2.5 standard (15.0 μg/m3). Philadelphia-Wilmington annual PM2.5

nonattainment area’s 2006 annual design value is 15.2 μg/m3

and its twenty-four hour 

design value is 36.5 μg/m3. This is below the 1997 twenty-four hour PM2.5 standard (65 

μg/m3

). Philadelphia-Wilmington annual PM2.5 nonattainment area will need to 

demonstrate that it will attain of the annual PM2.5 standard by no later than five years 

from the final designation date of April 5, 2005 (April, 2010). 
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Figure 1-1 Philadelphia-Wilmington Annual PM2.5 Nonattainment Area 

There are eight (8) monitoring sites currently operating in the Philadelphia-Wilmington 

annual PM2.5 nonattainment area. The Department operates several types of PM2.5

monitors within the Philadelphia-Wilmington annual PM2.5 nonattainment area; four (4) 

Federal Reference Method (FRM) samplers, two (2) PM2.5 speciation monitors and two 

(2) continuous PM2.5 monitor. FRM sampling began in January of 1999 and speciated 

sampling began in April of 2002. Sample frequencies for the Philadelphia-Wilmington 

FRM monitors range from once per day (1/1) to once every three days (1/3) and once 

every six days (1/6) for the speciated samplers. One of the continuous PM2.5 monitors 

has been operational since October 2003 while another became operational in May of 

2006. Measurements from the continuous monitor are generally used for air-quality 

forecasting purposes and cannot be used to determine attainment status. 
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1.3 Philadelphia-Wilmington Data Analysis Summary 

Table 1-1 lists the historic PM2.5 concentrations in the Philadelphia-Wilmington annual 

PM2.5 nonattainment area. Historic FRM data indicate the Philadelphia-Wilmington 

annual PM2.5 nonattainment area has consistently exceeded the health-based annual PM2.5

standard since the Department began sampling (see Figure 1-2). 

Table 1-1 Historic Design Values: Philadelphia-Wilmington annual PM2.5

Nonattainment Area 

Year 98th 24-Hour 24-Hour 

Design Value 

Annual Annual 

Design Value 

2000 15.99 

2001 39.5 15.86 

2002 31.9 14.73 15.5 

2003 37.8 36 15.29 15.3 

2004 30.5 33 15.02 15.0 

2005 37.0 35 16.51 15.6 

2006 36.7 35 13.99 15.2 

Annual standard: 15.0 μg/m3 Twenty-four hour standard 65 μg/m3

Figure 1-2 Annual Design Values: Philadelphia-Wilmington annual PM2.5

Nonattainment Area

Philadelphia-Wilmington Nonattainment Area

Annual PM2.5 Concentrations

12.00

13.00

14.00

15.00

16.00

17.00

18.00

19.00

2000 2001 2002 2003 2004 2005 2006

Concentrations (ug/m3) 

Annual

Annual Design Value

Annual Standard
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The Department has reviewed FRM, speciated and continuous PM2.5 data within the 

Philadelphia-Wilmington annual PM2.5 nonattainment area. More detailed analyses are 

included in Appendices A, B and C. Results from these appendices form the basis of our 

general conceptual model. As more analyses are completed in the future, our conceptual 

model may need to be updated. 

A short list of findings is set forth below: 

• The majority of FRM monitors within the Philadelphia-Wilmington annual 

PM2.5 nonattainment area appear to have significant trends (see Appendix E). 

The bulk of these trends appear to be downward. Decreases in annual PM2.5 

concentrations may be due to emission reductions in the mobile-source sector 

since many of the trend monitors are located near major highways. 

• The major components in the speciated data are sulfates, organic carbon, nitrates 

and ammonium. Component percentages for speciated monitors within the 

Philadelphia-Wilmington annual PM2.5 nonattainment area are similar to results 

from nearby speciated monitors. 

• Results from Norristown’s continuous TEOM monitor are very similar to the 

corresponding FRM values indicating results from the continuous monitor are a 

good reflection of actual concentrations on days when an FRM sample is not 

collected. 

• Additional observations from the Norristown continuous monitor: 

o Continuous measurements run slightly higher than the corresponding 

FRM measurements. 

o Jump in hourly concentrations during the “morning rush” due to 

increased highway traffic. This jump is less apparent over the weekend. 

o Overnight concentrations are only slightly higher than daytime 

concentrations. This is probably due to local meteorology with overnight 

emissions “pooling” under the nighttime inversion then mixing away 

during the day. 

o Weekend concentrations are generally lower than weekday 

concentrations indicating a strong anthropogenic component. 

• Monitors within southeast Pennsylvania generally correlate well with each other 

though correlations are not as good between southeast Pennsylvania and 

monitors to the west (Lancaster County) and north (Northumberland County). 

• The Chester and 500 Broad Street (Philadelphia County) monitors do not 

correlate as well with other monitors in southeast Pennsylvania suggesting some 

deviations at these sites from the overall trends in the region. 

1.4 Technical Committees 

PA DEP staff in consultation with staff from other state agencies will work together to 

reach decisions regarding technical issues concerning modeling and monitored design 

values. Any questions or issues that cannot be answered by this group will be forwarded 

to the appropriate staff in the U.S. EPA Region III. 
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1.5 Participating Organizations 

The PA DEP will be the primary developer of the Commonwealth’s modeling 

demonstration. The Allegheny County Health Department will prepare the modeling 

demonstration for the Liberty-Clarton annual PM2.5 nonattainment area in western 

Pennsylvania. Both agencies maintain periodic contact with one another during the SIP 

development process. Other organizations involved in developing the Commonwealth’s 

modeling demonstration include the Ozone Transport Commission’s (OTC) Modeling 

Workgroup, the Mid-Atlantic/Northeast Visibility Union (MANE-VU) and the Northeast 

States for Coordinated Air Use Management (NESCAUM). 

1.6 Schedule for Completion 

Pennsylvania is currently working with other members of the Ozone Transport 

Commission’s (OTC) Modeling Workgroup to complete the PM2.5 modeling 

demonstration. This modeling demonstration builds on the group’s ozone SIP modeling 

platform. Modeling work should be completed before the end of 2007 to allow adequate 

time for the states to prepare SIP demonstrations by April 2008. 

2.0 Model and Modeling Inputs 

The modeling demonstration for the Philadelphia-Wilmington annual PM2.5

nonattainment area relies heavily on the OTC SIP quality-modeling platform. Ozone 

modeling was the primary focus of this effort. This group’s interaction with the MidAtlantic/Northeast Visibility Union (MANE-VU) and the Northeast States for 

Coordinated Air Use Management (NESCAUM) allowed it, through the regional 

modeling centers, to do additional year-round modeling for PM2.5 and Regional Haze. 

The PA DEP has been an active participant in the OTC’s modeling workgroup. The 

Department provided the necessary emissions files for Pennsylvania sources needed to 

run the photochemical grid model used in the SIP modeling platform. The following 

sections provide brief summaries of the OTC modeling study. More detailed information 

can be found in the OTC documentation produced as part of this modeling analysis. 

Several of these documents are included in the reference section and in Appendix B. 

2.1 Selection of Air Quality, Meteorological and Other Model Inputs 

The U.S. EPA’s current guidance does not recommend a particular model or models for 

use in a SIP attainment demonstration. The OTC modeling committee used the 

Community Multi-scale Air Quality (CMAQ) photochemical grid model (version 4.5) as 

part of its SIP modeling platform (OTC Final Modeling Protocol, 2006). CMAQ is a 
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Eulerian grid model capable of simulating air-pollutant concentrations in the atmosphere 

using mathematical equations to characterize chemical and physical properties. 

Meteorological and emission input files must be prepared regardless of which 

photochemical grid model is used. The regional fine-particulate modeling analysis will 

encompass an entire year of simulation (2002). This should provide a good variety of 

episodes to characterize Philadelphia-Wilmington’s annual PM2.5 nonattainment. 

2.2 Modeling Domain 

Figure 2-1 shows the modeling domain used by the OTC. A nested-grid approach is used 

with the lower resolution outer grid providing boundary conditions for a more refined 

grid covering the area of interest. The modeling domain was chosen to be large enough 

to properly simulate regional transport. The outer domain boundary is far enough from 

the inner grid’s boundary so that clean-boundary condition assumptions are realistic and 

probably do not unduly influence concentrations within the inner domain. 

Figure 2-1 OTC Modeling Study Domain 

Outer grid at 36-kilometer resolution, inner grid at 12-kilometer resolution

2.3 Horizontal and Vertical Grid Resolution 

The inner (fine) grid covering the northeast region and the Philadelphia-Wilmington 

nonattainment area has a horizontal grid resolution of 12 km. CMAQ’s horizontal grid 

resolution matches the grid resolution of the meteorological model (MM5). This 

proposed resolution is within the upper range of the fine-grid resolution size 
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recommended in the U.S. EPA’s draft modeling guidance document. The resolution 

should be adequate to realistically simulate regional air-quality within the PhiladelphiaWilmington annual PM2.5 nonattainment area. 

The model’s vertical resolution is also in part defined by the vertical resolution of the 

meteorological model (MM5). The definition of the vertical structure could also have 

adopted the one-to-one resolution of the meteorological model. However, based upon 

prior experience, the vertical extent of the model was set around a height of six to eight 

km. The number of vertical layers permitted in the model is limited by computational 

considerations as well as storage limits; too many layers increase the amount of time 

needed to complete a simulation and the amount of information being stored, processed 

and exchanged. Limiting the vertical resolution to a few layers, however, would 

inherently discard the detailed information provided by the meteorological model. A 

compromise solution would be to maintain the high resolution with a one-to-one design 

of the vertical layers up to approximately one or two km yielding around 7 to 10 levels, 

followed by a collapse of the MM5 upper layers to around six to eight km to form 

another six to eight levels. Thus, under this scenario there would be a total of 13 to 18 

layers in the vertical with 7 to 10 levels below two km and the remaining between two 

and eight km. It should be noted that the mid-point of layer 1 in this analysis is around 

10 m. 

2.4 Model Initial and Boundary Conditions 

The photochemical grid model will be started three days before the start of the analysis 

period using “clean” conditions across the domain. Prior experiences have shown that a 

three-day ramp-up period is sufficient to establish pollutant levels that are encountered in 

the beginning of an episode. 

In prior studies, attempts have been made to include any information that is available 

from monitors that are near the western and northern boundaries of the modeling domain. 

For this modeling analysis, similar attempts will be made to obtain pollutant data at the 

boundaries. “Clean” conditions, however, will be assumed for the outer model 

boundaries if reliable data is not available. 

2.5 Near-Scale Modeling 

A near-scale modeling analyses may be necessary if the regional model fails to 

demonstrate that the Philadelphia-Wilmington annual PM2.5 nonattainment area will meet 

the health-basted annual PM2.5 standard. In this case, the Department will use a 

Lagrangian or Gaussian model to examine primary particulate in accordance with 

applicable guidance. The approach will be similar to what the Allegheny County Health 

Department has proposed for its Liberty-Clairton annual PM2.5 nonattainment area. 
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2.6 Episode Selection 

The OTC modeling study simulated for all of 2002 instead of the episodic approach. 

This should allow for an adequate analysis of Philadelphia-Wilmington’s annual PM2.5

nonattainment since it will include periods of low and elevated fine-particulate 

concentrations. 

Attainment demonstrations have typically been based on a limited number of episodes 

which are in turn are made up of a limited number of days when pollutant concentrations 

exceeding the NAAQS. Episodes are chosen on the basis of peak concentrations and the 

representativeness of the atmospheric conditions that typically occurred during times of 

elevated pollutant concentrations. Philadelphia-Wilmington annual PM2.5 nonattainment 

area violates the annual fine-particulate standard so it is important to consider conditions 

during the entire year not just episodes when concentrations are high. 

Typically computational and resource constraints limited the number of episodes used in 

a demonstration. Advances in computer capabilities and expanded resources have 

permitted groups like the OTC modeling group to simulate longer periods of time. The 

current OTC modeling study has proposed simulating all of 2002 using a regional 

photochemical grid model. This approach has several advantages. The first advantage 

being the greater variety of episodes the modeling demonstration can examine. This 

makes the analysis more robust and increases confidence that emission reductions will be 

beneficial over a number of atmospheric conditions that lead to elevated fine-particulate 

concentrations. The second advantage is 2002 coincides with the U.S. EPA’s choice to 

build the base emission inventory. This coincidence will lead to more confidence in the 

photochemical model’s ability to simulate actual fine-particulate concentrations based on 

the base inventory (modeled 2002 concentrations will be based on 2002 emissions and 

compared with actual monitored 2002 concentrations). 

2.7 Meteorological Model 

The meteorological files used in CMAQ were produced using the Pennsylvania State 

University/National Center for Atmospheric Research (PSU/NCAR) mesoscale model 

more commonly know as MM5. MM5 is a limited-area, nonhydrostatic, terrainfollowing sigma-coordinate model designed to simulate or predict mesoscale atmospheric 

circulation. The model is publicly available and has been used for various air-quality 

modeling studies in the past. Additional information regarding MM5 can be found in 

Appendix B (OTC Documentation - Meteorological Modeling using Penn State/NCAR 

5th Generation Mesoscale Model, MM5). 
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2.8 Emission Inputs 

The OTC Modeling Committee also examined two emissions processors (EMS2001 and 

SMOKE, both using CB4 chemistry) in its prior work and concluded that there are 

differences between them that could be minimized by forcing the models to use a 

common speciation and surrogate database. OTC documentation included in Appendix B 

(Emission Processing for the Revised 2002 OTC Regional and Urban 12 km Base Case 

Simulations) details on how the emission inventories were built and processed. 

For areas with an attainment date of no later than April 5, 2010 for the annual PM2.5

NAAQS, the emission reductions need to be implemented no later than the beginning of 

the 2009. A determination of attainment will likely be based on air-quality monitoring 

data collected in 2007, 2008, and 2009. Therefore, the year to project future emissions 

should be no later than the last year of the three-year monitoring period; in this case 

2009. 

The 2002 base year emissions inventory shall be projected to 2009 using standard 

emissions projection techniques. 2009 inventories developed by MANE-VU shall be 

used in the attainment demonstration. The most recently available inventories from other 

RPOs in the modeling domain will be used. 

Emission inventory guidance documents will be followed for developing projection year 

inventories for point, area, mobile, and biogenic emissions. These procedures address 

projections of spatial, temporal, and chemical composition change between the base year 

and projection year. 

The control strategies developed for evaluation in the attainment demonstration will be 

selected by the OTC’s Control Strategy Committee. These will be selected from groups 

of strategies developed by the technical subcommittees responsible for identifying and 

developing the regulations and/or control measures. 

Consideration will be given to maintaining consistency with control measures likely to be 

implemented by other modeling domains that may be involved in region-wide analysis. 

Also, technology-based emission reduction requirements mandated by the Clean Air Act 

will be included in the future year model runs. 

2.9 Area Examined in the Attainment Demonstration 

The Philadelphia-Wilmington annual PM2.5 nonattainment area is a multi-state 

nonattainment area consisting of five (5) counties in Pennsylvania, one in Delaware and 

three (3) in New Jersey. Three types of fine–particulate monitors operated during 2002; 

FRM samplers, speciated samplers and continuous monitors. Quarterly relative reduction 
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factors (RRFs) will be calculated using the OTC’s modeling results for all monitors in the 

Philadelphia-Wilmington annual PM2.5 nonattainment area. RRFs have to be determined 

for each PM2.5 component in accordance with the U.S. EPA’s modeling guidance 

document. 

The two speciated monitors operated by the Department did not begin operations until 

April 2002. RRFs for the first quarter will have to be based on a mean first quarter 

values or some other methodology in accordance with the U.S. EPA modeling guidance 

document. 

Unusual weather conditions contributed to massive fires in the northern portion of 

Canada’s Quebec province in early July 2002. The plume from this fire impacted both 

fine particulate and ozone concentrations across much of the northeast for several days 

(Northeast Oxidant and Particle study NE-OPS, 2002). Data (July 6-9, 2002) from 

almost all of the FRM monitors in southeast Pennsylvania including Chester were 

invalidated as an “exceptional event” under the U.S. EPA guidelines. 

2.10 Quality Assurance 

All air quality, emissions, and meteorological data will be reviewed to ensure 

completeness, accuracy, and consistency before proceeding with modeling. Any errors, 

missing data or inconsistencies, will be addressed using appropriate methods that are 

consistent with standard practices. 

Quality Assurance (QA) activities will be carried out for the various emissions, 

meteorological, and photochemical modeling components of the modeling study. 

Emissions inventories obtained from the various Regional Planning Organizations (RPO) 

will be examined through the use of quality assurance software, algorithms, and plotting 

routines to check for errors in the emissions estimates. When such errors are discovered, 

the problems in the input data files shall be corrected. 

Emission inventories from the MANE-VU RPO are currently undergoing final 

preparation and quality assurance tests. The OTC intends to use the most current 

emission inventory data from the other RPOs that are contained within the modeling 

domain. The other RPOs may revise their emission inventories after the OTC 

commences its modeling analysis. These changes will not be incorporated into the 

OTC’s modeling analysis due to time constraints. Emission inventory changes made by 

the other RPOs are expected to be small and therefore only contribute to minor changes 

in fine-particulate concentrations within the OTR. 

The MM5 meteorological and CMAQ air quality model inputs and outputs will be plotted 

and examined to ensure accurate representation of the observed data in the model-ready 

fields, and temporal and spatial consistency and reasonableness. Both MM5 and CMAQ 

will undergo an operational/scientific evaluation and this will facilitate, among other 

things, the quality assurance review of the meteorological and air quality modeling 

procedures. Data sets available to support this quality assurance of the aerometric inputs 
12 

include the routine synoptic-scale data sets from the NWS 12-hourly rawinsondes and 

three-hourly surface observations. These data include the horizontal wind components (u 

and v), temperature (T), and relative humidity (q) at the standard pressure levels, plus 

sea-level pressure (SLP) and ground temperature (Tg). 

The OTC Modeling workgroup has completed several analyses of the MM5 

meteorological files used in the group’s modeling analysis. Analyses of the MM5 

meteorological fields are located in Appendix C. OTC’s most resent analysis of MM5 

was to examine the effects of different Planetary Boundary Layer (PBL) schemes on the 

meteorological fields. Three different PBL schemes were examined using meteorological 

information including temperature, wind speed, wind direct and humidity from over 600 

National Weather Service (NWS) and CASTNet (Clean Air Status and Trends Network). 

MM5 was found to produce meteorological fields that were in general agreement with 

corresponding observations. 

3.0 Model Performance Evaluation 

A model performance evaluation will be conducted to ensure the regional photochemical 

model is simulating fine-particulate concentrations in a reasonable fashion. If the 

regional photochemical model reproduces the fine-particulate components well, then it 

lends more credibility to the model’s ability to simulate fine-particulate concentrations 

correctly for the control strategy runs. 

3.1 Ambient Data Base 

Model evaluations will need to be completed on all fine-particulate components. 

Evaluation matrices from the U.S. EPA’s draft modeling guidance document will be 

used. It is important that the regional photochemical model simulate the highest 

contributing fine-particulate components correctly. In Philadelphia-Wilmington annual 

PM2.5 nonattainment area’s case this would be sulfates, nitrates and organic carbon. 

Results from PA DEP’s speciated PM2.5 monitor will be used in this analysis. 

There are several additional sources of fine-particulate measurements that could be used 

in the model performance evaluation. These include Philadelphia-Wilmington’s FRM 

and continuous fine-particulate measurements and results from an acid rain monitoring 

site near Valley Forge. Data from the acid rain site is of limited use because the site only 

started collecting data in November of 2002. 

Other performance evaluation measures will have to be developed if the Department has 

to do additional “near-scale” modeling to demonstrate attainment. 
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3.2 Evaluation Procedures 

The U.S. EPA guidance will be used to evaluate model performance. Model PM2.5 bias 

statistics will be developed in accordance with section 18.4.2 of the guidance. These will 

be used to determine each PM2.5 component’s bias. Any large bias in PhiladelphiaWilmington’s sulfate, nitrate or organic PM2.5 components will be problematic. Initial 

model results presented at the OTC’s modeling committee member’s meetings suggest 

CMAQ simulates sulfate concentrations quite well. 

Continuous and FRM data will be used in a relative fashion to determine if there are any 

temporal biases in the model. These data sets contain more information than the 

speciated data sets because their collection frequency is greater, once every three days 

and hourly, versus the once every sixth day for the speciated data. 

4.0 Attainment Demonstration and other Supplemental Analyses 

The modeled attainment demonstration consists of analyses that estimate whether 

selected emissions reductions will result in ambient concentrations that meet the 

NAAQS, and an identified set of control measures which will result in the required 

emissions reductions. The attainment demonstration estimates the amount of emission 

reduction needed to demonstrate attainment by using a modeling attainment test. 

Additional analyses may also be performed to indicate that a proposed emission reduction 

will lead to attainment of the NAAQS. The modeled attainment test predicts whether or 

not all estimated future annual fine-particulate design values will be less than or equal to 

the concentration level specified in the NAAQS under meteorological conditions similar 

to those which have been simulated. 

4.1 Model Attainment Test 

The modeled PM2.5 attainment test applied at each nonattainment monitor will follow the 

recommended procedures outline in the U.S. EPA’s modeling guidance document. In 

order to perform the recommended modeled attainment test, States should divide 

observed mass concentrations of PM2.5 into 6 components5: 

• mass associated with sulfates (SO4); 

• mass associated with nitrates (NO3); 

• mass associated with organic carbon (OC); 

• mass associated with elemental carbon (EC); 

• mass associated with inorganic particulate emissions, excluding primary sulfate 

and 

• nitrate particles (IP); 
14 

• unattributed mass (i.e., the difference between measured PM2.5 and the sum of the 

other 5 components) (U). 

To apply the test, States must first have run an air quality model at least twice to simulate 

current emissions and to simulate the net effects of a proposed control strategy and 

growth projected to two years prior to the required attainment date. The Department will 

then follow the recommended procedures to develop the appropriate RRFs for each 

component. For each monitoring site, obtain modeled estimates for 5 of the 6 major 

components of observed PM2.5 (i.e., SO4, NO3, OC, EC and IP). For each 3-month quarter, 

calculate site (i) and component (j) specific relative reduction factors (RRF)ij. The 

relative reduction factor for component j at a site i is given by the following expression: 

(RRF)ij = ([Cj, projected]/[Cj, current])I 

where, 

Cj, current is the quarterly mean concentration predicted at or near the monitoring site 

with emissions characteristic of the period used to calculate the 

current design value for annual PM2.5 (e.g., 2000-2002); 

Cj, projected is the quarterly mean concentration predicted at or near the monitoring 

site two years prior to the required attainment date (e.g., 2010 in an area 

having a 2012 attainment date). 

Assume that the relative reduction factor for the sixth previously identified component of 

observed PM2.5 (i.e., “U”) is “1.00". Apply each component-specific relative reduction 

factor to the observed average quarterly mean concentration of the corresponding 

component, derived in step 1. Add the 6 components to obtain a projected average 

quarterly mean PM2.5 concentration.

4.2 Unmonitored Area Analysis 

In the event that it is necessary to estimate design values at unmonitored locations within 

the Philadelphia-Wilmington nonattainment area, an “unmonitored area analysis” using 

model adjusted spatial fields may be performed. The basic steps of this process are as 

follows: 

1. Interpolate ambient design value data to create a set of spatial fields. 

2. Adjust the spatial fields using gridded model output gradients (base year 

values). 

3. Apply gridded model RRFs to the model adjusted spatial fields. 

4. Determine if any unmonitored areas are predicted to exceed the NAAQS in 

the future. 

Recommended U.S. EPA guidance shall be utilized in the “unmonitored area analysis”. 
15 

4.3 Additional Analyses 

Corroboratory evidence shall accompany the model attainment demonstration. The U.S. 

EPA guidance for supplemental analyses and weight of evidence (WOE) demonstrations 

shall be followed. Table 1-2 summarizes the U.S. EPA guidelines used to determine if a 

WOE demonstration is needed. 

The weight of evidence submittal, if necessary, shall describe the analyses performed, 

databases used, key assumptions and outcomes of each analysis, and why the evidence, 

viewed as a whole, supports a conclusion that the area will attain the NAAQS despite the 

model predicted future design value, or conversely, demonstrate that reaching attainment 

is not likely despite passing the model attainment test. WOE analysis performance and 

type will be dictated by the U.S. EPA’s final modeling guidance. 

5.0 Procedural Requirements 

A range of documents will be prepared and referenced during the SIP process. 

Documents pertaining to the modeling analysis in support of Pennsylvania’s SIP for the 

Philadelphia-Wilmington annual PM2.5 nonattainment area will be made available as soon 

as practical for all interested parties. Additional documentation for the OTC Modeling 

Committee as part of its regional modeling analysis will be referenced and included in the 

documentation. 

Table 1-2 Summary of PM2.5 WOE Guidelines (from the U.S. EPA Guidance)

Results of Modeled Attainement Test Supplemental Analyses 

Annual PM2.5 24-Hour PM2.5

Future Design Value 

< 14.5 μg/m3

, all sites 

Future Design Value 

< 62 μg/m3

, all sites 

Basic supplemental analyses should be 

completed to confirm the outcome of the 

modeled attainment test 

Future Design Value 

14.5 – 15.5 μg/m3

, all 

sites 

Future Design Value 62 

– 67 μg/m3, all sites 

A weight of evidence demonstration 

should be conducted to determine if 

aggregate supplemental analyses support 

the modeled attainment test 

Future Design Value 

≥ 15.5 μg/m3, all sites 

Future Design Value 

≥ 68 μg/m3, all sites 

More qualitative results are less likely to 

support conclusion differing from the 

outcome of the modeled attainment test 
16 

5.1 Reporting 

Documents, technical memorandums, and data bases developed in this study will be 

submitted to all parties for review and subsequent distribution as appropriate. The 

various work products developed in preceding tasks will be synthesized and integrated to 

produce a draft Technical Support Document (TSD) that describes the full range of 

technical and modeling activities performed during the project. This report will contain 

the essential methods and results of the conceptual model, episode selection, modeling 

protocol, base case model development and performance testing, future year and control 

strategy modeling, quality assurance, weight of evidence analyses, and calculation of 

PM2.5 attainment via the U.S. EPA’s relative reduction factor (RRF) methodology. 

The PA DEP is the responsible agency for conducting and submitting a regional 

modeling attainment demonstration for June 15, 2009 to the U.S. EPA. All parties will 

work to establish a suitable outline for the TSD within the framework. A final TSD will 

be developed after receiving reviewer’s comments. 

5.2 Data Archive and Delivery of Modeling Files 

All relevant data sets, model codes, scripts, and related software required by any project 

participant necessary to corroborate the study findings (e.g., performance evaluations, 

control strategy runs) will be provided in an electronic format. The Department will be 

responsible for the archival of all modeling data relevant to this project. Transfer of data 

may be facilitated through the combination of a project website and the transfer of large 

databases via overnight mail. 

The department will work with U.S. EPA Region III staff to develop a full list of 

deliverables prior to the submittal of the final SIP demonstration. 

6.0 References 

The Modeling Committee of the Ozone Transport Commission, A Modeling Protocol 

for the OTC SIP Quality Modeling System For Assessment of the Ozone National 

Ambient Air Quality Standard in the Ozone Transport Region, March 2006. 

NorthEast Oxidant and Particle Study (NEOPS), Final Report to the Commonwealth 

of Pennsylvania, July 2003. 

The United States Environmental Protection Agency, Guidance on the Use of Models 

and Other Analyses for Demonstrating Attainment of Air Quality Goals for Ozone, 

PM2.5, and regional Haze, April 2007 (EPA –454/B-07-002).
A 

Appendix A.

Mid-Atlantic Regional Air Management Association (MARAMA) 

A Guide to Mid-Atlantic Regional Air Quality

< MARAMA report attached as a pdf document > 

http://www.marama.org/reports/Guide-MidAtlantic_RegAQ_Final.pdf 
A 

Appendix B. 

Summary of Pennsylvania’s PM2.5 Nonattainment Problem 
B 

Appendix C. 

Correlation Analysis: Southwest, Southcentral and Southeast Pennsylvania 
A 

Appendix D. 

OTC Documentation 
B 

Appendix E 

OTC Modeling Committee – Meteorological Modeling Analysis