# The Nature of the Ozone Air Quality Problem in the Ozone Transport Region: A Conceptual Description

Prepared for the Ozone Transport Commission

Prepared by NESCAUM Boston, MA

Final

October 2006

Contributing Authors

Tom Downs, Maine Department of Environmental Protection Richard Fields, Massachusetts Depart ment of Environmental Protection Prof. Robert Hudson, University of Maryland Iyad Kheirbek, NESCAUM Gary Kleiman, NESCAUM

Paul Miller, NESCAUM Leah Weiss, NESCAUM

### ii Acknowledgements

NESCAUM thanks the Mid-Atlantic Regi onal Air Management Association for providing the foundational ba sis of this report.

NESCAUM also thanks the following people for their comments and input during the development of this report:

Tad Aburn, Maryland Department of the Environment Michael Geigert, Connecticut Depart ment of Environmental Protection Kurt Kebschull, Connecticut Depart ment of Environmental Protection Tonalee Key, New Jersey Department of Environmental Protection Mohammed A. Majeed, Delaware Department of Natural Resources and Environmental

Conservation Charles Pietarinen, New Jersey Depa rtment of Environmental Protection Jeff Underhill, New Hampshire Department of Environmental Services David Wackter, Connecticut Depart ment of Environmental Protection Martha Webster, Maine Department of Environmental Protection Danny Wong, New Jersey Department of Environmental Protection Jung-Hun Woo, NESCAUM Michael Woodman, Maryland Department of the Environment

### iii 

## TABLE OF CONTENTS
Executive Summary........................................................................................................... vi

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

1.2. Ozone formation .............................................................................................. 1-2 1.3. Spatial pattern of ozone episodes in the OTR..................................................1-3 1.4. The regional extent of the ozone problem in the OTR ....................................1-4

1.5. Ozone trends in the OTR ................................................................................. 1-6 1.6. History of ozone transport science...................................................................1-7 1.6.1. From the 1970s to the National Research Council report, 1991..............1-7 1.6.2. Ozone Transport Assessm ent Group (OTAG) 1995-1997 ......................1-8 1.6.3. Northeast Oxidant and Particle Study (NE-OPS) 1998-2002.................. 1-9

1.6.4. NARSTO 2000....................................................................................... 1-10 1.6.5. New England Air Quality Study (NEAQS) 2002-2004.........................1-12 1.6.6. Regional Atmospheric Measuremen t, Modeling, and Prediction Program (RAMMPP) 2003...................................................................................................1-13 1.7. Summary........................................................................................................ 1-14 2. Meteorology and Evolution of Ozone Ep isodes in the Ozone Transport Region.... 2-1 2.1. Large-scale weather patterns............................................................................ 2-1 2.2. Meteorological mixing processes .................................................................... 2-2

2.2.1. Nocturnal inversions ................................................................................ 2-3

2.2.2. Subsidence inversions.............................................................................. 2-3 2.3. Meteorological tran sport processes..................................................................2-3

2.3.1. Introduction..............................................................................................2-3

2.3.2. Ground level winds..................................................................................2-5 2.3.3. Mid-level winds: Nocturnal low level jets...............................................2-7 2.3.4. Upper level winds: Ozone and precursors aloft.......................................2-9 2.4. Atmospheric modeling of regional ozone transport.......................................2-11 2.5. Summary........................................................................................................ 2-14 3. Ozone-forming Pollutant Emissions........................................................................ 3-1 3.1. Emissions inventory char acteristics in the OTR..............................................3-1 3.1.1. Volatile organic compounds (VOCs)....................................................... 3-1 3.1.2. Oxides of nitrogen (NO X 

### ) ........................................................................3-2 3.2. Emissions inventory charac teristics outside the OTR .....................................3-5

3.3. Are NO X 

### or VOC control strategies most effective at reducing ozone?..........3-7 3.4. Summary.......................................................................................................... 3-8

4. What Will It Take to Clean the Air?

– Linking the Science to Policy ....................4-1 4.1. The three phases of a bad ozone day and the ozone reservoir.........................4-1 4.2. Chronology of an ozone episode – August 2002.............................................4-3 4.3. Clean Air Act provisions .................................................................................4-9 4.4. Past regional efforts .......................................................................................4-10 4.5. Summary: Building upon success..................................................................4-11 Appendix A: USEPA Guidance on Ozone Conceptual Description .............................. A-1 Appendix B: Ozone pattern cla ssifications in the OTR.................................................. B-1 Appendix C: Exceedance days by monitor in the OTR.................................................. C-1 Appendix D: 8-hour ozone design va lues in the OTR, 1997-2005................................. D-1

### iv Appendix E: The sea breeze and flow over the ocean in-depth.......................................E-1 Appendix F: Observed nocturnal low leve l jet across the OTR, July 2002.....................F-1 Appendix G: Contributions to the ozone reservoir......................................................... G-1



## FIGURES
Figure 1-1. Conceptual picture of oz one formation in the atmosphere ........................... 1-3 Figure 1-2. Map of 8-hour ozone base line design values in the OTR .............................1-5 Figure 1-3. Trends in 8-hour ozone in the OTR 1997-2005............................................1-6 Figure 1-4. Conceptual picture of different transport regimes contributing to ozone episodes in the OTR............................................................................................1-12 Figure 2-1. Temperature profile taken over Albany, NY, on September 1, 2006 at 7 a.m.

eastern standard time............................................................................................. 2-2 Figure 2-2. Schematic of a typical weather patt ern associated with severe ozone episodes

in the OTR.............................................................................................................2-4 Figure 2-3. Illustration of a sea breeze and a land breeze................................................2-5 Figure 2-4. Average 2000 – 2002 wind direction frequency associated with elevated onehour ozone levels in coastal Maine .......................................................................2-6 Figure 2-5. Ozonesonde measurements on August 5, 2005 of elevated ozone

concentrations in a noc turnal low level jet a bove Beltsville, MD ........................2-9 Figure 2-6. Altitude profiles for ozone, carbon monoxide, NO Y 

### , and SO 2 

### taken on July 15, 1995 .......................................................................................................2-10 Figure 2-7. Observed vertical ozone profile measured a bove Poughkeepsie, NY at about 4 a.m. EST on July 14, 1995 ............................................................................... 2-11 Figure 3-1. 2002 MANE-VU state VOC inventories in the OTR ...................................3-2 Figure 3-2. State level nitr ogen oxides emissions ........................................................... 3-3 Figure 3-3. Plot of monitored NO X 

### trends in OTR during 1997-2005 ............................3-4 Figure 3-4. 2002 MANE-VU state NO X 

### inventories in the OTR ....................................3-5 Figure 4-1. Median ozone profiles for morn ing and afternoon flights from 1996 – 2003

............................................................................................................................... 4-1 Figure 4-2. Hourly ozone profiles in the southern OTR, August 12, 2002 .....................4-2 Figure 4-3. Hourly ozone profiles in the northern OTR, August 12, 2002......................4-3 Figure 4-4. Surface weather ma ps for August 9-16, 2002...............................................4-6 Figure 4-5. HYSPLIT 72-hour back tr ajectories for August 9-16, 2002.........................4-7 Figure 4-6. Spatially interpolated maps of maximum 8-hour surface ozone concentrations August 9 – 16, 2002 ..............................................................................................4-8



## TABLES
Table 2-1. USEPA CAIR modeling results of percent contribu tion to 8-hour ozone

nonattainment in OTR counties in 2010 due to transport from upwind states....2-12 Table 2-2. USEPA CAIR modeling results of upwind states that make a significant

contribution to 8-hour ozone in downw ind OTR nonattainment counties..........2-13

Table 3-1. Eastern U.S. RPOs and their state members................................................... 3-6

Table 3-2. VOC emissions in eastern RPOs .................................................................... 3-6

Table 3-3. NO X 

### emissions in eastern RPOs..................................................................... 3-7

### v

### vi 

# Executive Summary

The Ozone Transport Region (OTR) of the eastern United States covers a large area that is home to over 62 million people li ving in Connecticut, Delaware, the District of Columbia, Maine, Maryland, Massachuset ts, New Hampshire, New Jersey, New York, Pennsylvania, Rhode Island, Vermont, and northern Virginia. Each summer, the people who live within the OTR are subject to ep isodes of poor air qual ity resulting from ground-level ozone pollution that affects much of the region. During severe ozone events, the scale of the problem can extend beyond the OTR’s borders and include over 200,000 square miles across the eastern United States. Contributing to the problem are

local sources of air pollution as well as ai r pollution transported hundreds of miles from

distant sources outside the OTR.

To address the ozone problem, the Clean Air Act Amendments require states to develop State Implementation Plans (SIPs) de tailing their approaches for reducing ozone pollution. As part of this process, states are urged by the U.S. Environmental Protection Agency (USEPA) to include in their SIPs a conceptual description of the pollution problem in their nonattainment areas. This doc ument provides the c onceptual description of the ozone problem in the OTR states, consistent with the USEPA’s guidance.

Since the late 1970s, a wealth of inform ation has been collected concerning the regional nature of the OTR’s ground-level oz one air quality problem. Scientific studies have uncovered a rich complexity in the in teraction of meteorol ogy and topography with ozone formation and transport. The evolution of severe ozone episodes in the eastern U.S. often begins with the passage of a large high pressure area from the Midwest to the middle or southern Atlantic states, where it assimilates into and becomes an extension of the Atlantic (Bermuda) high pressure system. During its passage east, the air mass accumulates air pollutants emitted by large coal -fired power plants and other sources located outside the OTR. Later, sources with in the OTR make their own contributions to the air pollution burden. These expansive w eather systems favor the formation of ozone by creating a vast area of clear skies and hi gh temperatures. These two prerequisites for abundant ozone formation are further compound ed by a circulation pattern favorable for pollution transport over large distances. In the worst cases, the high pressure systems stall over the eastern United States for days, crea ting ozone episodes of strong intensity and long duration.

One transport mechanism that has fairly recently come to light and can play a key role in moving pollution long distances is the noc turnal low level jet. The jet is a regional scale phenomenon of higher wind speeds that often forms during ozone events a few hundred meters above the ground just above th e stable nocturnal boundary layer. It can convey air pollution several hundreds of m iles overnight from the southwest to the northeast, directly in line with the major population centers of th e Northeast Corridor stretching from Washington, DC to Boston, Massachusetts. The nocturnal low level jet can extend the entire length of the corrido r from Virginia to Maine, and has been observed as far south as Georgi a. It can thus be a transport mechanism for bringing ozone and other air pollutants into the OTR from out side the region, as well as move locally formed air pollution from one part of the OTR to another.

### vii Other transport mechanisms occur over smaller scales. These include land, sea, mountain, and valley breezes that can selectively affect relatively local areas. They play a vital role in drawing ozone-laden air into some areas, such as coastal Maine, that are far removed from major source regions.

With the knowledge of the different transp ort scales into and within the OTR, a conceptual picture of bad ozone days emerge s. After sunset, the gr ound cools faster than the air above it, creating a noc turnal temperature inversion. This stable boundary layer extends from the ground to only a few hundred meters in altitude. Above this layer, a nocturnal low level jet can form with highe r velocity winds rela tive to the surrounding air. It forms from the fairly abrupt removal of frictional forces induced by the ground that

would otherwise slow the wind. Absent this friction, winds at this height are free to accelerate, forming the nocturnal low level jet. Ozone above the stable nocturnal inversion layer is likewise cut off from the gr ound, and thus it is no t subject to removal

on surfaces or chemical destruction fr om low level emissions. Ozone in high

concentrations can be entrained in the noctu rnal low level jet and transported several hundred kilometers downwind overnight. The ne xt morning as the sun heats the Earth’s surface, the nocturnal boundary layer begins to break up, and the ozone transported overnight mixes down to the surface where conc entrations rise rapidly, partly from mixing and partly from ozone generated lo cally. By the afternoon, abundant sunshine combined with warm temperatures prom otes additional photochemical production of ozone from local emissions. As a result, ozone concentrations reach their maximum levels through the combined effects of local and transported pollution.

Ozone moving over water is, like ozone alof t, isolated from destructive forces. When ozone gets transported into coastal re gions by bay, lake, and sea breezes arising from afternoon temperature contrasts between the land and water, it can arrive highly

concentrated.

During severe ozone episodes associated with high pressure systems, these multiple transport features are embedded with in a large ozone reservoir arriving from source regions to the south and west of th e OTR. Thus a severe ozone episode can contain elements of long range air polluti on transport from outside the OTR, regional scale transport within the OTR from channeled flows in nocturnal low level jets, and local transport along coastal shores due to bay, lake, and sea breezes.

From this conceptual description of ozone formation and transport into and within the OTR, air quality planners need to devel op an understanding of what it will take to clean the air in the OTR. Weather is always changing, so every ozone episode is unique in its specific details. The relative influences of the transport pathways and local emissions vary by hour and day during the c ourse of an ozone episode and between episodes. The smaller scale weather pattern s that affect pollution accumulation and its transport underscore the importance of local (i n-state) controls for emissions of nitrogen oxides (NO X 

### ) and volatile organic compounds (VOCs), the main precursors of ozone formation in the atmosphere. Larger synop tic scale weather patterns, and pollution patterns associated with them, support the need for NO X 

### controls across the broader

eastern United States. Studies and characteri zations of nocturnal low level jets also support the need for local and regional controls on NO X 

### and VOC sources as locally generated and transported pollution can both be entrained in nocturnal low level jets

### viii formed during nighttime hours. The presence of land, sea, mountain, and valley breezes indicate that there are unique aspects of pollution accumulation and transport that are area-specific and will warrant policy respons es at the local and regional levels beyond a one-size-fits-all approach.

The mix of emission controls is also important. Regional ozone formation is primarily due to NO X 

### , but VOCs are also important because they influence how efficiently ozone is produced by NO X 

### , particularly within urban centers. While reductions in anthropogenic VOCs will typically have less of an impact on the long-range transport of ozone, they can be effective in reduci ng ozone in urban areas where ozone production may be limited by the availability of VOCs. Therefore, a combination of localized VOC

reductions in urban centers with additional NO X 

### reductions across a larger region will help to reduce ozone and precursors in nonattainment areas as well as downwind transport across the entire region.

The recognition that ground-level ozone in the eastern United States is a regional problem requiring a regional solution marks one of the greatest advances in air quality management in the United States. Duri ng the 1990s, air quality planners began developing and implementing coordinated regi onal and local control strategies for NO X 

### and VOC emissions that went beyond the pr evious emphasis on urban-only measures. These measures have resulted in significant improvements in air quality across the OTR.

Measured NO X 

### emissions and ambient concentrations have dropped between 1997 and 2005, and the frequency and magnitude of oz one exceedances have declined within the

OTR. To maintain the current momentum for improving air quality so that the OTR states can meet their attainment deadlines, there co ntinues to be a need for more regional NO X 

### reductions coupled with appropriate local NO X 

### and VOC controls.The Nature of the Ozone Air Quality Problem in th e Northeast: A Conceptual Description Page 1-1



# 1. INTRODUCTION

1.1. Background

Ground-level ozone is a persistent public health problem in the Ozone Transport Region (OTR), a large geographical area that is home to over 62 million people living in Connecticut, Delaware, the District of Columbia, Maine, Maryland, Massachusetts, New Hampshire, New Jersey, New York, Pennsylvania, Rhode Island, Vermont, and northern Virginia. Breathing ozone in the air harms lung tissue, and creates the risk of permanently damaging the lungs. It reduces lung functi on, making breathing more difficult and causing shortness of breath. It aggravates ex isting asthmatic conditions, thus potentially triggering asthma attacks that send children and others suffering from the disease to hospital emergency rooms. Ozone places at particular risk those with preexisting respiratory illnesses, such as emphysema and bronchitis, and it may reduce the body’s ability to fight off bacterial infections in the respiratory system. Ground-level ozone also affects otherwise healthy children and adults wh o are very active, eith er at work or at play, during times of high ozone levels (USEPA, 1999). In addition, recent evidence suggests that short-term ozone exposure ha s potential cardiovascular effects that may

increase the risk of h eart attack, stroke, or even death (USEPA, 2006).

The Clean Air Act requires states that have areas designated “nonattainment” of the ozone National Ambient Air Quality Standard (NAAQS) to submit State Implementation Plans (SIPs) demonstrating how they plan to attain the ozone NAAQS. The SIPs must also include regulations that will yield the necessa ry emission reductions

to attain the national ozone health standard . As part of the SIP process, the U.S. Environmental Protection Agency (USEPA) urges states to include a conceptual description of the pollution problem in their nonattainment areas. The USEPA has provided guidance on developing a conceptual description, which is contained in Chapter 8 of the document “Guidance on th e Use of Models and Other Analyses in

Attainment Demonstrations for the 8-hour Ozone NAAQS” (EPA-454/R-05-002, October 2005) (Appendix A of this report re produces Chapter 8 of the USEPA guidance document). a 

### This document provides the conceptual description of the ozone problem in the OTR states, consistent with the USEP A’s guidance. In the guidance, the USEPA recommends addressing three questions to help define the ozone problem in a nonattainment area: (1) Is regional transport an important factor? (2) What types of meteorological episodes lead to high ozone? (3) Is ozone limited by availability of volatile organic compounds, nitrogen oxides, or combinations of the two, and therefore which source categories may be most important to control? This report addresses these

a At the time of this writing, the USEPA was incorpor ating Section 8 of the 8-hour ozone guidance into a new USEPA guidance document covering ozone, PM 2.5 , and regional haze. The new guidance is in Section 11 of Draft 3.2 “Guidance on the Use of Models and other Analyses for Demonstrating Attainment of Air Quality Goals for Ozone, PM 2.5 , and Regional Haze,” U.S. EPA, (Draft 3.2 – September 2006),

available at http://www.epa.gov/ttn/scram/guidance_sip.htm#pm2.5 (accessed Oct. 5, 2006). The newer guidance, when finalized, may differ in some respects from the text given in Section 8 of the earlier ozone guidance.The Nature of the Ozone Air Quality Problem in th e Northeast: A Conceptual Description Page 1-2



### questions, as well as provides some in-depth da ta and analyses that can assist states in developing conceptual descriptions tailored to their specific areas, where appropriate.



## 1.2. Ozone formation

Ground-level ozone is formed in the atmosphere through a series of complex chemical reactions involving sunlight, wa rm temperatures, nitrogen oxides (NO X 

### ) and volatile organic compounds (VOCs). Figure 1-1 is a conceptual picture of the emission

sources and conditions contri buting to ozone formation in the atmosphere. There are natural (biogenic) sources of NO X 

### , such as formation by soil microbes, lightening, and forest fires, but the dominant NO X 

### sources in the eastern Unit ed States arise from human activities, particularly the bur ning of fossil fuels in cars, tr ucks, power plants, and other combustion sources (MARAMA, 2005).

In contrast to NO X 

### sources, there are significant bi ogenic sources of VOCs in the eastern United States that can play an impor tant contributing role in ozone formation. Isoprene, a highly reactive natural VOC emitted typically by deciduous trees such as oak, is an important ozone precursor across la rge parts of the East. Isoprene emissions typically increase with temperature up to a poi nt before high temperat ures tend to shut off emissions as leaf stomata (pores) close to reduce water loss. The tendency for increasing isoprene emissions with increasing temperat ures (up to a point) coincides with the temperature and sunlight conditions fa vorable for increased ozone production (MARAMA, 2005).

Human-caused (anthropogenic) VOC emissi ons are important and may dominate the VOC emissions by mass (weight) in an urban area, even though natural sources dominate in the overall region. Some anthr opogenic VOCs, such as benzene, are toxic, and may increase risks of cancer or lead to other adverse health effects in addition to helping form ozone (MARAMA, 2005).The Nature of the Ozone Air Quality Problem in th e Northeast: A Conceptual Description Page 1-3



### Figure 1-1. Conceptual picture of ozone formation in the atmosphere

Picture provided by the Maryland Department of the Environment.



### The relationship between the relative importance of NO X 

### and VOC emissions in producing ozone is complex. The relative ratio of NO X 

### and VOC levels in the local atmosphere can affect the efficiency of local urban ozone production, and this can vary by time (hour or day) at the same urban loca tion, as well as across locations within the same urban area. High NO X 

### concentrations relative to VOC levels may hinder ozone production through the destruction of ozone by NO X 

### (sometimes called “NO X 

### scavenging”). The same NO X 

### , however, when diluted relative to VOCs through the downwind transport and dispersal of a pollution plume, will promote ozone formation

elsewhere.



## 1.3. Spatial pattern of ozon e episodes in the OTR

The day-to-day pattern of ground-level ozone varies a ccording to meteorological variables that include, but are not limited to , sunlight, air temperature, wind speed, and wind direction. Generally within the OTR, one would expect elevated ozone to occur more frequently in southernmost areas, where solar elevation angles are greater and cold frontal passages are fewer. A glance at m onthly composite maps (for example, JulyAugust 2002) at the USEPA AIRNOW website seems to confirm this ( http://www.epa.gov/airnow/nemapselect.html ). On some days, however, one notes that the highest ozone levels shift northward to mainly affect the northern part of the OTR. Other shifts are apparent between coastal and interior areas.

This variability of the daily ozone pattern is tied to variations in the atmosphere’s circulations over a range of scales, and how geographic features influence theseThe Nature of the Ozone Air Quality Problem in th e Northeast: A Conceptual Description Page 1-4



### circulations. These features can includ e boundaries between land and sea, and the influence of the Appalachian Mountains on winds to their east over the Atlantic Coastal

Plain.

For the OTR, Stoeckenius and Kemball-C ook (2005) have iden tified five general ozone patterns: (1) high ozone throughout th e OTR; (2) high ozone confined to the extreme southeastern OTR; (3) high ozone along the I-95 corridor and northern New England; (4) high ozone in the western OTR; and (5) generally low ozone throughout the OTR. However, not all ozone episodes necessari ly neatly fit into one of the five general patterns as daily conditions will vary and a given ozone episode may have characteristics that fall across several class types. These five general patterns, however, are a useful classification scheme for characterizing how re presentative an historical ozone episode is for possible use in air quality planning effort s. Appendix B presents the descriptions of the five general ozone patterns and their meteorological attributes as developed by Stoeckenius and Kemball-Cook (2005).



## 1.4. The regional extent of the ozone problem in the OTR

Air monitoring demonstrates that areas with ozone problems in the OTR do not exist in isolation. The map of Figure 1-2 show s an extensive pattern of closely adjacent ozone nonattainment in areas throughout th e OTR. The 8-hour ozone baseline design values (defined in the figure caption) at the monitoring sites shown in the figure indicate extensive areas throughout the OTR with ma ny monitors having values above the 8-hour ozone NAAQS of 0.08 ppm. In practice, this corresponds to levels equal to or greater than 0.085 ppm (equivalent to 85 ppb). The ma p also shows that many monitors outside the designated nonattainment areas of the OTR al so record elevated ozone concentrations approaching the 8-hour ozone NAAQS (i.e., 75- 84.9 ppb), even if not violating it. The many monitoring locations acro ss that OTR measuring elevated ozone levels that approach or exceed the 8-hour ozone NAAQS give a strong indication of the regional nature of the OTR’s ozone problem.The Nature of the Ozone Air Quality Problem in the Northeast: A Conceptual DescriptionPage 1-5Figure 1-2. Map of 8-hour ozone baseline design values in the OTRNote: A monitor’s baseline design value is the average of the three design values (3-year averages of the 4th maximum 8-hour ozone level) for the set of years 2000-2002, 2001-2003, and 2002-2004. The figure shows the regionalnature of ozone levels in the OTR,with a number of closely adjacent nonattainment areas (baseline design values≥85 ppb)along with a broader region of elevated regional ozone (e.g., baseline design values≥75 ppb) (figure by Michael Geigert, Connecticut Department of Environmental Protection).The Nature of the Ozone Air Quality Problem in th e Northeast: A Conceptual Description Page 1-6



## 1.5. Ozone trends in the OTR

The number of 8-hour ozone exceedance days vary year-to-year in the OTR, which is largely driven by variations in meteorology. During warmer summers conducive for ozone formation, the number of ex ceedance days at individual monitors in nonattainment areas of the OTR has been freque nt, typically with 10 or more days above the 8-hour ozone NAAQS during the course of the summer. Figure 1-3 displays the variation in exceedance days when collectivel y considering all monitoring sites across the OTR since 1997. The figure also includes a li ne indicating the tre nd in the maximum 8-

hour ozone concentrations observed in the OTR each year. The variation in exceedance days from year-to-year makes it difficult to di scern a clear trend, although there is some hint that the number of exceedance days may be declining in recent years. There appears to be a stronger indication of a declini ng maximum 8-hour ozone concentration in the OTR since 1997, although the maximum con centration remains well above the 8-hour ozone NAAQS. This reflects the impact of numerous control strategies implemented locally, regionally, and nationally to reduce em issions of the precursor pollutants that contribute to ozone formation in the atmosphere.

Figure 1-3. Trends in 8-hour ozone in the OTR 1997-2005

Note: The bars correspond to the number of 8-hour ozone exce edance days per year. The up per blue line indicates

the trend in maximum 8-hour ozone concentrations in the OTR during 1997-2005. The lower red horizontal line indicates the level of the 8-hour ozone NAAQS (functionall y 0.085 ppm). (Figure created by Tom Downs, Maine Dept. of Environmental Protection.)



### The tables in Appendix C contain the frequency of ozone exceedance days for

individual monitors in the OTR states from 1997 to 2005. Appendix D contains tables for the 8-hour ozone design values recorded at ozone monitors in the OTR during 1997- 1997-2005 OZONE SEASON 8-HOUR OZONE EXCEEDANCE DAYS AND MAXIMUM 8-hr

OZONE CONCENTRATION TRENDS IN THE OTR

0 10 20 30 40 50 60 70 80 90

1997 1998 1999 2000 2001 2002 2003 2004 2005

YEAR# 8-hr OZONE EXCEEDANCE DAYS

0.00 0.01 0.02 0.03 0.04 0.05 0.06 0.07 0.08 0.09 0.10 0.11 0.12 0.13 0.14 0.15 0.168-HOUR CONCENTRATION (ppm)

# EXCEEDANCE DAYS MAXIMUM 8-hr OZONE 8-hour ozone NAAQS level

0.085 1997-2005 OZONE SEASON 8-HOUR OZONE EXCEEDANCE DAYS AND MAXIMUM 8-hr

OZONE CONCENTRATION TRENDS IN THE OTR

0 10 20 30 40 50 60 70 80 90

1997 1998 1999 2000 2001 2002 2003 2004 2005

YEAR# 8-hr OZONE EXCEEDANCE DAYS

0.00 0.01 0.02 0.03 0.04 0.05 0.06 0.07 0.08 0.09 0.10 0.11 0.12 0.13 0.14 0.15 0.168-HOUR CONCENTRATION (ppm)

# EXCEEDANCE DAYS MAXIMUM 8-hr OZONE 8-hour ozone NAAQS level

0.085The Nature of the Ozone Air Quality Problem in th e Northeast: A Conceptual Description Page 1-7



### 2005. These tables give an indication of th e number of monitors in the OTR since 1997 that have exceeded the 8-hour NAAQS of 85 ppb (equal to 0.085 ppm in the tables of Appendix D) at some point in time.



## 1.6. History of ozone transport science

1.6.1. From the 1970s to the National Research Council report, 1991

Research studies conducted in the 1970s gave some of the earliest indications that pollution transport plays an important role in contributing to air pollution problems in the OTR. An aircraft study in the summer of 1979 tracked a mass of ozone-laden air and its precursors leaving central Ohio, crossing the length of Pennsylvania, and entering the Northeast Corridor where it contributed upw ards of 90 ppb to early morning ozone concentrations in the OTR prior to local oz one formation from local emissions (Clarke & Ching, 1983). Wolff and Lioy (1980) described a “river of ozone” extending from the Gulf Coast through the Midwest and into New England. A number of early studies also documented the role of large coal-fired power plants in forming significant amounts of ozone pollution that traveled far downwind fr om the power plant source and contributed to a large elevated backgr ound of regional ozone (Davis et al. , 1974; Miller et al. , 1978; Gillani & Wilson, 1980; Gillani et al. , 1981; White et al. , 1983). Section 2 below describes in more depth the observed meteor ological processes identified as the ozone transport mechanisms important for the OTR.

On a regional scale, NO X 

### emissions within areas of high VOC emissions, such as forested regions rich in isoprene, will pr oduce elevated levels of ozone. A number of studies have now established that regional oz one formation over the eastern United States is limited primarily by the supply of anthropogenic NO X 

### , with anthropogenic VOCs having less regional influence compared to their potential urban influence. This is due to the presence of significant amounts of natu ral VOCs across broad areas of the eastern United States (Trainer et al. , 1987; Chameides et al. , 1988; Sillman et al. , 1990; McKeen

et al. , 1991; Chameides et al. , 1992; Trainer et al. , 1993; Jacob et al. , 1993).

The presence of dispersed NO X 

### emissions sources, such as coal-fired power plants, in rural regions rich in isoprene an d other natural VOC emissions from trees and other vegetation often leads to elevated regi onal ozone during the summer months. This ozone can then be transported into urban areas where it contributes to high background concentrations during the early morning hour s before local production of ozone occurs from local precursor emissions (both NO X 

### and VOCs).

In 1991, a National Research Council (NRC) committee, synthesizing the best

available information at the time on ozone form ation and transport in the eastern United States, reported (NRC, 1991):

High ozone episodes last from 3-4 days on av erage, occur as many as 7-10 times a year, and are of large spatia l scale: >600,000 km 2 . Maximum values of non-urban ozone commonly exceed 90 ppb during these episodes , compared with av erage daily maximum values of 60 ppb in summer. An urban area n eed contribute an increment of only 30 ppb over the regional background during a high ozone episode to cause a violation of the National Ambient Air Quality Standard (NAAQS) in a downwind area. ... Given the regional nature of the ozone problem in the eastern United States, a regional model is needed to develop control strategies for individual urban areas.The Nature of the Ozone Air Quality Problem in th e Northeast: A Conceptual Description Page 1-8

[Note: The NRC discussion was in the context of the ozone NAAQS at the time of the NRC report, which was 0.12 ppm (120 ppb) averaged over one hour.]



### The observed ozone spat ial scale of >600,000 km 2 

### (>200,000 square miles) is comparable to the combined size of Kentucky, Ohio, West Virginia, Pennsylvania, Maryland, New York, and New Jersey. Add itional field studies and modeling efforts since the NRC report (described below) have reinforced its basic findings and provide a consistent and coherent body of evidence fo r transport throughout the eastern United

States.



## 1.6.2. Ozone Transport Assessmen t Group (OTAG) 1995-1997

The increasing regulatory focus on broader regional approaches to ozone control beyond the OTR began with the Ozone Transport Assessment Group (OTAG) in 1995. OTAG was a partnership between the USEPA, the Environmental Council of the States (ECOS), state and federal government o fficials, industry organizations, and environmental groups. OTAG’s goal was “to develop an assessment of and consensus agreement for strategies to reduce ground-leve l ozone and its precursors in the eastern United States” (OTAG, 1997a). The effort assessed transport of ground-level ozone

across state boundaries in the 37-state OTAG region and developed a set of recommendations to the USEPA. OTAG completed its work in 1997.

OTAG supported a significant modeling effo rt of four regional ozone episodes

across the eastern United States. OT AG’s Regional and Urban Scale Modeling Workgroup found that on a regional scale, modeled NO X 

### reductions produced widespread

ozone decreases across the eastern United Stat es with limited ozone increases generally

confined to some urban areas. Also on a re gional scale, VOC reductions resulted in limited ozone decreases gene rally confined to urba n areas (OTAG, 1997b).

The OTAG Air Quality Analysis Wor kgroup provided additional observational and other analytical results to inform model interpretation and the development of OTAG recommendations. Among its many finding, this Workgroup observed:

Low wind speeds (< 3 m/sec) enable the accumul ation of ozone near local source areas. High winds (> 6 m/sec) reduce the concentrations but contribute to the long-range transport of ozone. The average range of ozone transport implied from an array of diverse methods is between 150 miles and 500 miles. However, the perceived range depends on whether one considers the average concentrations (300–500 miles) or peak concentrations (tens of miles at 120 ppb). The relative importance of ozone transport for the attainment of the new 80 ppb 8-hour standard is likely to be higher due to the closer proximity of nonattainment areas. (OTAG, 1997c)



### Based on the variety of technical work performed by multiple stakeholders during the process, OTAG reached a number of ma jor conclusions (OTAG, 1997d), including:

• Regional NO X reductions are effective in pro ducing ozone benefits; the more NO X reduced, the greater the benefit.

• Ozone benefits are greatest in the subregions wh ere emissions reductions are made; the benefits

decrease with distance.

• Both elevated (from tall stacks) and low-level NO X reductions are effective.

• VOC controls are effective in reducing ozone locally and are most a dvantageous to urban

nonattainment areas.The Nature of the Ozone Air Quality Problem in th e Northeast: A Conceptual Description Page 1-9

• Air quality data indicate that ozone is pervasive, th at ozone is transported, and that ozone aloft is carried over and transported from one day to the next.



### The technical findings of OTAG workgroups were consistent with the modeling and observational studies of regional ozone in the eastern United States already appearing

in the scientific literature at that time.

Through its work, OTAG engaged a broa d group outside of the scientific community in the discussion of ozone transpor t. This brought a grea ter understanding of the role of ozone transport across the eastern Un ited States that was then translated into air quality policy with the creation of a re gional ozone control strategy focusing on the

reduction of NO X 

### emissions from power plants.



## 1.6.3. Northeast Oxidant and Particle Study (NE-OPS) 1998-2002

The Northeast Oxidant and Particle St udy (NE-OPS) began in 1998 as a USEPA sponsored project to study air quality issu es in the Northeast. The study undertook four major field programs at a field site in nor theastern Philadelphia during the summers of 1998, 1999, 2001, and 2002. It involved a collaborative effort among research groups from a number of universities, government laboratories, and repr esentatives of the electric power industry in an investigation of the interp lay between the meteorological and chemical processes that lead to air pol lution events in the Northeast. A suite of measurement techniques at and above the earth’s surface gave a three-dimensional regional scale picture of the atmosphere. The studies found that horizontal transport aloft and vertical mixing to the surface are key factor s in controlling the evolution and severity of air pollution episodes in the Northeast (Philbrick et al. , 2003a).

At the conclusion of the 2002 summer fiel d study, the NE-OPS researchers were

able to draw several conclusions about ai r pollution episodes in Philadelphia and draw

inferences from this to the conditions in th e broader region. These include (Philbrick

et al. , 2003b):

• Transported air pollution from distant sources was a major contributor to all of the major summer air pollution episodes observed in the Philadelphia area.

• Regional scale meteorology is the major factor controlling the magnitude and timing of air pollution episodes.

• Knowledge of how the planetary boundary layer evolve s over the course of a day is a critical input for modeling air pollutant concentrations because it establishes the mixing volume.

• Remote sensing and vertical profiling technique s are critical for understanding the processes governing air pollution episodes.

• Ground-based sensors do not detect high levels of ozone that are frequently trapped and transported in layers above the surface.

• Horizontal and vertical nighttime transport proce sses, such as the nocturnal low level jets and “dynamical bursting” b events, are frequent contributors of pollutants during the major episodes.

• Specific meteorological conditions are important in catalyzing the region for development of major air pollution episodes.

• Tethered balloon and lidar measurements suggest a very rapid down mixing of species from the residual boundary layer during the early morning hours that is too large to be accounted for on the

basis of NO X reactions alone.

b “Dynamical bursting” events occur in the early morning hours due to instabilities in the lower atmosphere caused by differences in wind spee ds at different altitudes below the layer of maximum winds. Bursting events can vertically mix air down wards to the surface (see Philbrick et al., 2003b at p. 36).The Nature of the Ozone Air Quality Problem in the Northeast: A Conceptual Description Page 1-10

• Summer organic aerosols in Philadelphia consist of a relatively constant level of primary organic particulate matter, punctuated by extreme episodes with high levels of secondary organic aerosol during ozone events. Primary organic particulate matter is both biogenic and anthropogenic in nature, with the relative importance fluctuating from day to day, and possibly associated more strongly with northwest winds. Secondary aerosol formation events may be responsible for dramatic increases in particulat e organic carbon, while the rela tively constant contribution of primary sources could make a greater contributio n to annual average particulate levels. More research is needed to sort out the relative contributions of anthropogenic and biogenic sources.



### The findings on nocturnal low level jets o ccurring in concert with ozone pollution episodes are particularly salient for air qual ity planning for the OTR. In 19 of 21 cases

where researchers observed nocturnal low level jets during the NE-OPS 2002 summer campaign in the Philadelphia area, they al so saw peak 1-hour ozone levels exceeding 100 ppbv. The nocturnal low level jets were capable of transporti ng pollutants in air parcels over distances of 200 to 400 km. The fiel d measurements indicat ing that these jets often occur during periods of large scale stagnation in the region demonstrate the important role nocturnal low level jets can pl ay in effectively tran sporting air pollutants during air pollution episodes (Philbrick et al. , 2003b).

The upper air observations using tethered balloons and lidar indicated the presence of high pollutant con centrations trapped in a residual layer above the surface, thus preserving the pollutants from destructi on closer to the surface. Ozone, for example, when trapped in an upper layer during nightti me hours is not subjec t to destruction by

NO X 

### scavenging from low-level emission sources (i.e., cars and trucks) or deposition to surfaces like vegetation, hence it is availa ble for horizontal transport by nocturnal low level jets. The following day, it can vertical ly transport back down to the surface through “bursting events” and daytime convection. Wh en involving an upper layer of ozone-laden air horizontally transported overnight by a noc turnal low level jet, downward mixing can

increase surface ozone concentrations in the mo rning that is not the result of local ozone production (Philbrick et al. , 2003b).



## 1.6.4. NARSTO 2000

NARSTO (formerly known as the North American Research Strategy for Tropospheric Ozone) produced “An Assessmen t of Tropospheric Ozone Pollution – A North American Perspective” in 2000 to provide a policy-relevant re search assessment of ozone issues in North America (NARSTO, 2000). While the NARSTO Assessment is continental in scope, it encompasses issues re levant to the OTR, including results from a NARSTO-Northeast (NARSTO-NE) field campaign.

Several policy-relevant findings from the NARSTO Assessment are of relevance to the OTR (NARSTO, 2000):

• Available information indicates that ozone a ccumulation is strongly influenced by extendedperiods of limited mixing, recirculation of polluted air between the ground and aloft, and the longrange transport of ozone and its precursors. As a result, air quality management strategies require accounting for emissions from distan t as well as local sources.

• Local VOC emission reductions may be effective in reducing ozone in urban centers, while NO X emission reductions become more effective at distances removed from urban centers and other major precursor emissions.

• The presence of biogenic emi ssions complicates the manageme nt of controllable precursor emissions and influences the relative importance of VOC and NO X controls.The Nature of the Ozone Air Quality Problem in the Northeast: A Conceptual Description Page 1-11

• The effectiveness of VOC and NO X control strategies is not uniquely defined by the location or nature of emissions. It is now recognized that the relative effectiveness of VOC and NO X controls may change from one location to another and even from episode to episode at the same location.



### The NARSTO Assessment identified th e stagnation of synoptic scale (>1000 km 2 

### ) high pressure systems as a commonly occurring weather event leading to ozone pollution episodes. These systems are warm air masses associated with weak winds, subsiding air from above, and str ong inversions capping the planetary boundary level in the central region of the high. The wa rm air mass can settle into place for days to more than a week, and in the eastern U.S. te nd to slowly track from west to east during the summer. These conditions result in the build up of pollution from local sources with reduced dispersion out of the region. In term s of air quality, the overall appearance of such systems is the presence of numerous lo cal or urban-scale ozone pollution episodes embedded within a broader regional backgr ound of elevated ozone concentrations (NARSTO, 2000 at p. 3-34).

While stagnation implies little movement , the NARSTO Assessment found that a variety of processes can lead to long-range transport of air pollut ants that initially accumulated in these large-scale stagnation events. Over time, pollution plumes meander, merge, and circulate within the high pressu re system. Because of the difference in pressures, pollutant plumes that eventually migrate to the edges of a high pressure system get caught in increasing winds at the edge regions, creating more homogeneous regional pollution patterns. Stronger winds aloft captu re the regional pollutant load, and can transport it for hundreds of kilometers dow nwind of the stagnated air mass’s center (NARSTO, 2000 at p. 3-34). For example, air flow from west to east over the Appalachian Mountains can move air pollution originating within the Ohio River Valley

into the OTR.

Studies undertaken by the NARSTO-NE fi eld program also observed several regional scale meteorological features arising from geographical features in the eastern U.S. that affect pollutant transport. One im portant feature is the channeled flow of a nocturnal low level jet moving air pollution from the southwest to the northeast along the Northeast Corridor during overnight hours. The NARSTO-NE field program observed nocturnal low level jets on most nights preceding regional ozone episodes in the OTR, consistent with the observations of the NE-OPS campaign.

Another important smaller scale transport mechanism is the coastal sea breeze that can sweep ashore pollutants originally transported over the ocean parallel to the coastline. An example of this is the high oz one levels seen at times along coastal Maine

that move in from the Gulf of Maine after having been transported in pollution plumes from Boston, New York City, and other Nort heast Corridor locations (NARSTO, 2000 at pp. 3-34 through 3-37).

As a result of the NARSTO-NE field program, a conceptual picture of pollution transport into and within the OTR is possible. It consists of a combination of large-scale synoptic flow from the Midwest interacti ng with various regional and smaller-scale transport and meteorological features within the OTR, as illustrated in Figure 1-4. Synoptic-scale transport from west to east ac ross the Appalachian Mountains occurs with the slow-moving stagnant high pressure systems that foster large regional ozone episodes across eastern U.S. Regional-scale channeled flows, specifically nocturnal low level jetsThe Nature of the Ozone Air Quality Problem in the Northeast: A Conceptual Description Page 1-12



### from the southwest to the northeast along the A tlantic Coastal Plain, can occur within the synoptic system. In addition, daytime sea bre ezes can significantly affect bay and coast line air pollution levels within the OT R (NARSTO, 2000 at 3-36 and 3-37, citing

Blumenthal et al. , 1997).

Figure 1-4. Conceptual picture of different transport regimes contributing to ozone episodes in the OTR

Long-range (synoptic scale) transport occurs from west to east acr oss the Appalachian Mountains. Regional scale transport in channeled flows also occurs from west to east through gaps in the Appalachian Mountains and in nocturnal low level jets from southwest to northeast over the Northeast Corridor. Daytime sea breezes can affe ct local coastal areas by bringing in air pollution originally transported near the surface across wa ter parallel to the coast (e.g., along the Maine coastline). Figure from NARSTO, 2000, citing Blumenthal et al. , 1997.



## 1.6.5. New England Air Quality Study (NEAQS) 2002-2004

The New England Air Quality Study (N EAQS) has to date conducted field campaigns during the summers of 2002 and 2004 to investigate air quality on the Eastern Seaboard and transport of North American emissions into the North Atlantic (NEAQS, 2002). Transport of air pollution into the Gulf of Maine and subse quently into coastal areas of northern New England re ceived extensive attention.

High ozone levels in northern New Engla nd occur with light to moderate winds from source regions in the Northeast urban co rridor, rather than under locally stagnant conditions. The most important transport path ways leading to high ozone in coastal New Hampshire and Maine are over water rather than over land. Transport over water is particularly important in this northern region of the OTR for several reasons. First, there is a persistent pool of cooler water in the northern and easte rn Gulf of Maine and Bay ofThe Nature of the Ozone Air Quality Problem in the Northeast: A Conceptual Description Page 1-13



### Fundy. This creates a smoother transport su rface for air polluta nts relative to land transport, with a decrease in convective (vertical) mixing. S econd, deposition of pollutants to the water surface is very sma ll compared to the more rapid deposition occurring on land. Third, the lack of convect ive mixing allows pollution to be transported

in different directions in layers at different heights in the atmosphere (Angevine et al.

, 2004).

During the summer of 2002, researcher s observed two transp ort events into coastal northern New England. The first o ccurring on July 22 through July 23 involved large-scale synoptic transport in a 400-600 m layer over the Gu lf of Maine that was in

contact with the water’s surface. The southw esterly flow brought ozone pollution up from the New York City, Boston and other northeas tern urban locations into coastal northern New England. Ozone monitors on Maine’s coast extending from the New Hampshire

border to Acadia National Park recorded el evated 1-hour average ozone levels between 88 and 120 ppb during this period. In a late r episode during August 11-14, ozone and

wind observations indicated the role of local-scale transport via a sea breeze (southeasterly flow) bringing higher ozone levels into coastal New Hampshire from a polluted layer originally transported off shor e in the Gulf of Maine in a southwesterly flow arising out of the Northeast urban corr idor. Transport in an elevated layer also occurred with higher ozone recorded at a monitor on Cadillac Mountain in Acadia

National Park relative to two monitors located at lower elevations in the park (Angevine

et al. , 2004).

The results of NEAQS indicate the impor tant conditions contributing to ozone transport along the northern New England coast. The cool waters of the Gulf of Maine allow for transport of air pollutants over dist ances of 20-200 km in stable layers at the

water’s surface with lit tle pollutant deposition or dilution. Sea breezes can modify largescale synoptic transport over the ocean and brin g high ozone levels into particular sites located on the coast. Transport within higher layers above the Gulf of Maine can carry pollutants over much greater distances, 200-2000 km (Angevine et al. , 2004).



## 1.6.6. Regional Atmospheric Measuremen t, Modeling, and Prediction Program (RAMMPP) 2003

The Regional Atmospheric Measurement, Modeling, and Prediction Program (RAMMPP) is a program led by researchers at the University of Maryland. Its focus is developing a state-of-the-art scientific research tool to improve understanding of air quality in the mid-Atlantic region of the United States. It has a number of facets, including ozone and PM 2.5 

### pollutant level forecasti ng, aircraft, and surface measurements, real-time weather forecasting, and chemical transport modeling.

During the August 2003 electrical blackout in the eastern United States, one of the largest in North American history, scientists with RAMMPP were able to obtain airborne measurements that directly recorded changes in air pollution due to the virtual shutdown of numerous coal-fired power plants acr oss a large part of this region (Marufu et al.

, 2004). Initially, aircraft measurements were collected early in the day on August 15, 2003 above western Maryland, which was outside the blackout region. These measurements were compared with aircraft measurements ta ken later that day over central Pennsylvania, about 24 hours into the blackout. The comp arison indicated a decrease in ozoneThe Nature of the Ozone Air Quality Problem in the Northeast: A Conceptual Description Page 1-14



### concentrations of ~50 percen t within the blackout region (a s well as >90 percent decrease

in SO 2 

### and ~70 percent reduction in light scatte red by particles). These reductions were also consistent with comparisons to measur ements obtained over central Pennsylvania the previous year during a period of similar synoptic patterns as occurred during the blackout. Forward trajectories indicated that the decrease in ai r pollution during the

blackout benefited much of the eastern Unite d States. The decrease in ozone was greater than expected based on estimates of th e relative contributi on of power plant NO X 

### emissions to ozone formation in the region. Th e researchers suggested that this could be due to underestimation of power plant emi ssions, poor representation of power plant plumes in emission models, or an incomplete set of atmospheric chemical reactions in photochemical models. This accidental “real world” experiment indicates that ozone formation across a large part of the eastern Un ited States is sensitive to power plant NO X 

### emissions, and may be even more sensitive to NO X 

### reductions from these sources than currently predicted by air quality modeling.



## 1.7. Summary

The chemistry of ozone formation in th e atmosphere involves reactions of NO X 

### and VOC emissions from numerous sources during periods of warm temperatures and abundant sunshine. The day-to-day pattern of ground-level ozone in the OTR varies according to a number of meteorological variables, such as sunlight, temperature, wind speed, and wind direction. High levels of ozone within the OTR do not occur in isolation, indicating a broad regional air quality problem. Trends in 8- hour ozone levels since 1997 indicate improvement in air quality, a re flection of numerous control strategies implemented locally, regionally, and nationally to reduce emissions of the pollutants that

contribute to ozone formation.

The scientific literature pr ior to 1985 contains a number of peer reviewed papers describing observed episodes of ozone and precursor pollutant transport. In 1991, a

National Research Council re port summarized the state-of-the-science, which further highlighted the broad regional nature of the oz one problem in the eastern U.S. Since then, multiple collaborative efforts and field campaigns have further investigated specific aspects of the regional ozone problem affecting the OTR, and these provide a significant foundational basis for informed policy decisions to improve air quality.The Nature of the Ozone Air Quality Problem in the Northeast: A Conceptual Description Page 1-15



## References

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Blumenthal, D.L., F. Lurmann, N. Kumar., T. Dye, S. Ray, M. Korc, R. Londergan, and

G. Moore. Transport and mixing phenomena related to ozone exceedances in the

northeast U.S. EPRI Report TR-109523, Electric Powe r Research Institute, Palo Alto, CA, 1997.

Chameides, W.L., R.W. Lindsay, J. Richardson, and C.S. Kiang. “The role of biogenic hydrocarbons in urban photochemical smog: Atlanta as a case study.” Science 241 , 1473- 1475, 1988.

Chameides, W.L., F. Fehsenfeld, M.O. Rodgers, C. Cardelino, J. Martinez, D. Parrish, W. Lonneman, D.R. Lawson, R.A. Rasmussen, P. Zimmerman, J. Greenberg, P. Middleton, and T. Wang. “Ozone precursor relationships in the ambient atmosphere.” J. Geophys.

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Clarke, J.F., and J.K.S. Ching. “Aircraft observa tions of regional transport of ozone in the

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Davis, D.D., G. Smith, and G. Klauber. “Tra ce gas analysis of power plant plumes via

aircraft measurement: O 3 

### , NO X 

### , and SO 2 

### chemistry.” Science 186 , 733-736, 1974.

Gillani, N.V., and W.E. Wilson. “Formation and transport of ozone and aerosols in power plant plumes.” Annals N.Y. Acad. Sciences 338 , 276-296, 1980.

Gillani, N.V., S. Kohli, and W.E. Wilson. “Gas -to-particle conversion of sulfur in power plant plumes – I. Parameterization of the c onversion rate for dry, moderately polluted

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Jacob, D.J., J.A. Logan, G.M. Gardner, R.M. Yevich, C.M. Spivakovsky, S.C. Wofsy, S. Sillman, and M.J. Prather. “Factors regulating ozone over the United States and its export to the global atmosphere.” J. Geophys. Res. 98 , 14,817-14,826, 1993.

MARAMA (Mid-Atlantic Regional Air Management Association). A guide to midAtlantic regional air quality. MARAMA. Baltimore, MD, pp. 2-3, 2005 (available online at www.marama.org/reports ).

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R.R. Dickerson. “The 2003 North American electrical blackout: An accidental experiment in atmospheric chemistry.” Geophys. Res. Lett. 31 , L13106, doi:10.1029/2004GL019771, 2004.The Nature of the Ozone Air Quality Problem in the Northeast: A Conceptual Description Page 1-16



### McKeen, S.A., E.-Y. Hsie, and S.C. Liu. “A study of the dependence of rural ozone on ozone precursors in the eastern United States.” J. Geophys. Res. 96 , 15,377-15,394, 1991.

Miller, D.F., A.J. Alkezweeny, J.M. Hales, and R.N. Lee. “Ozone formation related to power plant emissions.” Science 202 , 1186-1188, 1978

NARSTO. An Assessment of Tropospheric Ozone Pollution . NARSTO, July 2000.

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, Appendix K

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.

OTAG (Ozone Transport Assessment Group). OTAG Technical Supporting Document

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.

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.

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83 rd 

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# 2. METEOROLOGY AND EVOLUTION OF OZONE

EPISODES IN THE OZONE TRANSPORT REGION

The following sections describe current knowledge of the factors contributing to ozone episodes in the OTR. The general desc ription of weather patterns comes mainly from the work of Ryan and Dickerson (2000) done for the Maryland Department of the

Environment. Further information is draw n from work by Hudson (2005) done for the Ozone Transport Commission and from a mid-A tlantic regional air quality guide by MARAMA (2005). The regional nature of the observed ozone episodes in the OTR is reinforced in modeling studies by the US EPA for the Clean Air Interstate Rule.



## 2.1. Large-scale weather patterns

Ryan and Dickerson (2000) have descri bed the general meteorological features conducive to ozone formation and transport that are pertinent to th e OTR. On the local scale, meteorological factors on which ozone concentrations depend are the amount of available sunlight (ultraviolet range), temp erature, and the amount of space (volume) in which precursor emissions mix. Sunlight drives the key photochemical reactions for ozone and its key precursors and the emissi ons rates of many precursors (isoprene for example) are temperature dependent. Emissions confined within a smaller volume result in higher concentrations of ozone. Winds in the lowest 2 km of the atmosphere cause horizontal mixing while vertical temperature an d moisture profiles dr ive vertical mixing. High ozone is typically associated with weather conditions of few clouds, strong temperature inversions, and light winds.

The large-scale weather pattern that co mbines meteorological factors conducive to high ozone is the presence of a region of upper air high pr essure (an upper air ridge)

with its central axis located west of the OTR. The OTR east of the axis of the highpressure ridge is characterized by subsid ing (downward moving) air. This reduces upward motion necessary for cloud formation, increases temperature, and supports a stronger lower level inversion. While the uppe r air ridge is located west of the OTR, surface high pressure is typically quite diffu se across the region. This pattern occurs throughout the year but is most common and longer lived in the summer months (Ryan and Dickerson, 2000).

The large, or synoptic, scale, weather pattern sketched above has important implications for transport into and within the OTR. First, the persistence of an upper air ridge west of the OTR drives generally west to northwest winds that can carry ozone generated outside the OTR into the OTR. A key point from this wind-driven transport mode is that stagnant air is not always a factor for high ozone episodes in the OTR. Second, the region in the vicinity of the ridge axis, being generally cloud free, will experience significant radiationa l cooling after sunset and therefore a strong nocturnal inversion will form. This inversion, typically only a few hundred meters deep, prevents ozone and its precursors from mixing downwar d overnight. Above the inversion layer, there is no opportunity for destruction of the pollutants by surface deposition, thus increasing the pollutants’ lifetimes aloft and co nsequently their transport distances. Third, with diffuse surface high pressure, smaller scale effects can become dominant in theThe Nature of the Ozone Air Quality Problem in th e Northeast: A Conceptual Description Page 2-2



### lowest layers of the atmosphere. These incl ude bay and land breezes, the Appalachian lee side trough, and the development of the nocturn al low level jet. Noct urnal low-level jets are commonly observed during high ozone ev ents in the OTR (Ryan and Dickerson, 2000).

As previously mentioned in Section 1, Stoeckenius and Kemball-Cook (2005) have identified five ozone patter ns in the OTR as a guide to an historical ozone episode’s representativeness for air quality planning purposes. They also described the meteorological conditions that are generally associated with each of these patterns. Appendix B presents the five types with the additional meteorological detail.



## 2.2. Meteorological mixing processes

An important element in the production of se vere ozone events is the ability of the atmosphere through temperature inversions to inhibit the mixing pr ocesses that under normal conditions would lead to dilution of the emitted pollutants. For the purposes of this discussion, we focus on two major classe s of temperature inversions, (1) nocturnal (radiative) and (2) subsidence.

Figure 2-1 shows an example of nocturn al and subsidence inversions in a temperature profile taken over Albany, NY, on September 1, 2006 at 7 a.m. eastern standard time. The figure shows two distinct temperature inversions

– the ground-based

nocturnal inversion and an inversion at a bout 1600 meters caused by the sinking motion (subsidence) of the atmosphere in a high pressure system.

Figure 2-1. Temperature profile taken ov er Albany, NY, on September 1, 2006 at

7 a.m. eastern standard time



## -40 -30 -20 -10 0 10 20 30 40 1000

925 850 700 500

Subsidence

Inversion

Nocturnal

Inversion

Temperature oC (red line)

Note: Blue line is dew point soundingAltitude mb



### 1600 m 3200 m

850 m



## -40 -30 -20 -10 0 10 20 30 40 1000

925 850 700 500

Subsidence

Inversion

Nocturnal

Inversion

Temperature oC (red line)

Note: Blue line is dew point soundingAltitude mb



## -40 -30 -20 -10 0 10 20 30 40 1000

925 850 700 500

Subsidence

Inversion

Nocturnal

Inversion

-40 -30 -20 -10 0 10 20 30 40 1000

925 850 700 500

-40 -30 -20 -10 0 10 20 30 40 1000

925 850 700 500

Subsidence

Inversion

Nocturnal

Inversion

Temperature oC (red line)

Note: Blue line is dew point soundingAltitude mb



### 1600 m 3200 m

850 mThe Nature of the Ozone Air Quality Problem in th e Northeast: A Conceptual Description Page 2-3



## 2.2.1. Nocturnal inversions

Land surfaces are far more efficient at ra diating heat than the atmosphere above, hence at night, the Earth’s surface cools more rapidly than the air. That temperature drop is then conveyed to the lowest hundred meters of the atmosphere. The air above this layer cools more slowly, and a temperature inve rsion forms. The inversion divides the atmosphere into two layers that do not mix. Below the nocturnal surface inversion, the surface winds are weak and any pollutant s emitted overnight accumulate. Above the inversion, winds continue through the night and can even become stronger as the

inversion isolates the winds from the friction of the rough surface.

In the morning, the sun warms the Earth’ s surface, and condu ction and convection transfer heat upward to warm the air near the surface. By about 10:00 – 11:00 a.m., the temperature of the surface has risen sufficiently to remove the inversion. Air from above

and below the inversion can then mix freel y. Depending on whethe r the air above the inversion is cleaner or more polluted than the air at the surface, th is mixing can either

lower or increase ai r pollution levels.



## 2.2.2. Subsidence inversions

Severe ozone events are usually associat ed with high pressure systems. In the upper atmosphere, the winds around a high pr essure system move in a clockwise direction. At the ground, friction between th e ground and the winds tu rns the winds away from the center of the system and “divergence” occurs, meaning that air at the surface moves away from the center. With the moveme nt of air horizontally away from the center of the high at the surface, air aloft moves ve rtically downward (or “subsides”) to replace the air that left. Thus, the divergence away from the high pressure system gives rise to subsidence of the atmosphere above the hi gh. The subsiding motion causes the air to warm as it moves downward and is compressed. As the warmer air meets the colder air below, it forms an inversion. A subsidence inve rsion is particularly strong because it is associated with this large scale downward motion of the atmosphere. The subsidence inversion caps pollution at a higher altitude in the atmo sphere (typically from 1200 to 2000 meters), and it is far more difficult to break down than the nocturnal inversion.

Hence the subsidence inversion limits vertical mixing in the middle of the day during an air pollution episode, keeping polluta nts trapped closer to the ground.



## 2.3. Meteorological transport processes

2.3.1. Introduction

Figure 2-2 shows the classic synoptic w eather pattern at the Earth’s surface associated with severe ozone episodes within the OTR. A quasi-stationary high pressure system (the Bermuda high) extends from th e Atlantic Ocean westward into interior southeastern U.S., where a second weaker high is located. Surface winds, circulating clockwise around the high, are es pecially light in the vicini ty of the secondary high. Farther north, a southwesterly flow streng thens toward New York and southern New England. This situation illustrates two circ ulation regimes often existing in OTR ozone episodes: more stagnant conditions in southern areas and a moderate transport flow in the

OTR from southwest to northeast. In additi on, as discussed previously, high pressureThe Nature of the Ozone Air Quality Problem in th e Northeast: A Conceptual Description Page 2-4



### systems exhibit subsidence, which results in temperature inversions aloft, and cloud free

skies.

Closer to the surface, the Appalachian Mountains induce changes in the wind field that also play important roles in the formation and transport of ozone in the OTR. The mountains act as a physical barrier confini ng, to some degree, pollution to the coastal plain. They also induce local effects such as mountain and valley breezes, which, in the case of down-slope winds, can raise surface temperatures thereby increasing chemical reactivity. In addition, mountai ns create a lee side trough, wh ich helps to channel a more concentrated ozone plume, and contribute to th e formation of nocturnal low level jets, the engine of rapid nighttime transport.

The Atlantic Ocean also plays a strong role during ozone episodes where sea breezes can draw either heavily ozone-laden or clean marine air into coastal areas.

Figure 2-2. Schematic of a typical weath er pattern associated with severe ozone episodes in the OTR

Meteorological processes that transport ozone and its precursors into and within the OTR can roughly be broken down into th ree levels: ground, mid and upper. The following sections discuss the three wind levels associated with meteorological transport processes in more detail.The Nature of the Ozone Air Quality Problem in th e Northeast: A Conceptual Description Page 2-5



## 2.3.2. Ground level winds

Land, sea, mountain, and valley breezes

In the OTR, land and sea breezes, and mountain and valley breezes can have an important influence on local air quality. These local winds are driven by a difference in temperature that produces a difference in pr essure. Figure 2-3 shows a schematic of the

formation of a sea breeze. The sea breeze fo rms in the afternoon when the land is considerably hotter than the ocean or bay. Ai r then flows from the high pressure over the ocean toward the low pressure over land. At night, the opposite may happen as the land cools to below the ocean’s temperature, and a land breeze blows out to sea. Because the nighttime land and water temperature differenc es are usually much smaller than in the day, the land breeze is weaker than the sea breeze. Sea breezes typically only penetrate a few kilometers inland because they are driv en by temperature contrasts that disappear

inland.

Figure 2-3. Illustration of a sea breeze and a land breeze

a) Sea Breeze b) Land Breeze Figure from Lutgens & Tarbuck , 2001.



### Along coastlines, such as coastal New Engl and, sea breezes bring in air pollution transported near the surface over water from urban locations located to the southwest. Figure 2-4 shows the average 2000-2002 wind di rection frequency for elevated 1-hour ozone in the vicinity of the Kennebec and Pe nobscot Rivers in Main e. There is a clear maximum of pollution in the direction of the sea breeze. These sites are located many miles upriver from the coast, and receive oz one transported over water from the sea up through the coastal bays and rivers.

In other cases, sea breezes can affect air quality in coastal cities because, under stagnant synoptic-scale winds, a city’s emi ssions may be recirculated or pushed back over land after having drifted out over the s ea earlier. Before se a breeze circulation begins, air pollution from a coastal city can mo ve out over the water. In the absence of a shift in winds due to a sea breeze, the city’s air pollution will be blown away. When a sea breeze circulation sets up, however, the pollute d air is pushed back toward the city. The sea breeze only pushes a few miles inland, wh ich is where the barrier to mixing lies. Later in the day, the air may be quite clean on the ocean side of th e city, but the air isThe Nature of the Ozone Air Quality Problem in th e Northeast: A Conceptual Description Page 2-6



### usually quite dirty on the inland side. The city suffers from its own recirculated pollution,

and also from the sea breeze that does not a llow pollution from the city to flow away from it. Appendix E presents more detailed information on sea breezes and flow over the ocean that contribute to ozone transport in parts of the OTR.

Figure 2-4. Average 2000 – 2002 wind direction frequency associated with elevated

one-hour ozone levels in coastal Maine

The bay breeze is a shallow circulati on over large inland bays, and may only extend a couple hundred meters above the surface. For example, bay breezes from the Chesapeake Bay often make Baltimore’s summ ertime air quality particularly poor. Air from the city cannot escape directly across th e Bay. On the other hand, a few miles closer to the Bay, conditions are often considerably cleaner, since no fresh emissions have gotten into the air there since earlier that morn ing. Polluted air from the west side of the Bay can still mix upward, where it meets th e stronger winds aloft, pass over the Bay

breeze circulation and come back dow n on the east side of the Bay.

Mountain and valley breezes are also driv en by a temperature contrast. In the daytime, the side of the mountain will heat up more quickly than the valley, and hence a flow from the valley to the mountain results. At night this flow is reversed as the mountain side cools more quickly than the va lley. As a result of these differences in cooling and heating, during the day, warm winds blow up toward the peaks from the valley below, while at night, cool air sink s and flows down the valley, settling in the lowest points. Local topography is very important in generating this phenomenon, making the breeze unique to a particular area.The Nature of the Ozone Air Quality Problem in th e Northeast: A Conceptual Description Page 2-7



### Mountains and valleys also serve to isolat e air in the valleys, while air at the mountaintops may be coming from very fa r away. Mountain winds, inversions, and mixing are quite complex. On a quiet ni ght, the mountaintop may be in the free troposphere, open to long-range transport, whil e the valley below is usually capped by a nocturnal inversion, isolati ng pollution in the valley. Air quality measurements taken during plane flights in the Shenandoah River Va lley have shown that the air pollutants in the valley may be rather different from the ai r at the nearby peaks. Cities on the western

side of the mountains will find that the A ppalachians are capable of damming pollution up against them (MARAMA, 2005 at pp. 42-43).



## Appalachian lee side trough

The Appalachian lee side trough forms on the leeward (downwind) side of the Appalachian Mountains. In a sense, it is the daytime companion to the nocturnal low level jet, discussed below, because it fo rms under similar stagnant conditions; however, the mechanism for its formation is different. In the OTR, a lee side trough forms when winds blow over the Appalachia n Mountains and down the lee side of the mountain range to the coastal plain. As the column descends down the lee side, it stretches vertically and spins faster, pulling up air a nd creating low pressure, thus rotating the winds to the

southwest. Because the air is typically rather dry, and the trough itself is rather weak, it does not usually lead to showers and thunde rstorms the way a trough associated with other weather systems would. It does cause wi nds to shift their direction, so a wind that

comes over the mountains from the west will turn and blow from the southwest along the coastal plain. Therefore, when surface winds on the coastal plain are from the southwest, if the Appalachian lee side tr ough is in place, it may be that the air actually came from the west, descended, and turned. The implication for air quality policy is straightforward. Pollution making its way over the mountains fr om the west will turn once it reaches the coastal plain and come from the southwest. Because surface winds are then from the southwest, when the Appalachian lee side troug h is in place, the limits of a nonattainment area’s airshed will be expanded farther south and west than they might otherwise be (MARAMA, 2005 at pp. 41-42). Studies have observed high ozone levels in the OTR

associated with a lee side trough east of the Appalachian Mo untains and aligned with the Northeast Corridor (Gaza, 1998; Kleinman et al. , 2004).



## 2.3.3. Mid-level winds: Noctur nal low level jets

The nocturnal low level c 

### jet is a localized region of rapid winds in the lower atmosphere (typically 500-1500 m above the gr ound level) that form at night under the same calm conditions often present in a pollution episode. Forming just above the nighttime temperature inversion mentioned previously, the nocturnal low level jet depends on the isolation from the surface provi ded by the inversion. It is primarily a nocturnal phenomenon that occurs more frequently during the spring and summer

seasons.

c “Low level” in this instance is relative to upper level jets occurring in the upper troposphere to lower stratosphere at heights of 10-15 km above the ground level. It is not a “ground level” phenomenon of the types described in the previous section.The Nature of the Ozone Air Quality Problem in th e Northeast: A Conceptual Description Page 2-8



### A nocturnal low level jet is generally found where a range of mountains meets a flat plain. There is a particularly strong nocturnal low level jet in the Great Plains of the

central United States on the eastern side of the Rocky Mountains. On the Eastern Seaboard, nocturnal low level jets develop al ong the Atlantic Coastal Plain located to the east of the Appalachian Mountai ns and to the west of the Atlantic Ocean. While the typical wind speed minimum of a nocturnal lo w level jet is often defined as more than 12 meters per second (m s -1 

### ), Ryan (2004) has proposed a weaker minimum speed

criterion of 8 m s -1 

### in the East because of the expected weaker terrain-induced forcing in this region. The mid-Atlantic nocturnal lo w level jet has a width of 300-400 km (to its half peak value) and a le ngth scale of more than 1500 km, following closely the orientation of the Appalachian Mountains.

The nocturnal low level jet forms when fronts and storm systems are far away. Surface winds are parallel to the terrain, wh ich in the case of the OTR is southwest running over the Atlantic Coastal Plain in front of the Appalachian Mountains. The nocturnal low level jet forms because land cools quicker than the air above it at night. The quickly cooling land results in the air cl osest to the surface cooling quicker than the air higher above. This creates a temperature inversion that separates the atmosphere into layers. The warmer air above the invers ion layer (~200-800 m above ground) loses the frictional effect of the surface and increases in speed. In the eastern United States, the nocturnal low level jet has been observed in Georgia, the Carolinas and Virginia (Weisman, 1990; Sjostedt et al. , 1990) in addition to the OTR (NARSTO, 2000). Appendix F describes a specific example of an observed nocturnal lo w level jet occurring over the length of the OTR during a period of high ozone in July 2002.

Upper air studies have observed ozone be ing transported overnight in nocturnal low level jets in the OTR (Woodman et al. , 2006). The Maryland Department of the Environment (MDE) operates an upper air profiler at the Howard University (HU) site located in Beltsville, Maryland. On August 5, 2005, two helium-filled balloons carrying ozone sensors (called “ozonesondes”) were la unched at the HU – Beltsville site in the early morning hours. Using the upper air prof iler, a nocturnal low level jet of 15 m s -1


### was observed between approximately midni ght and 7:30 a.m. One ozonesonde was

launched at 3:30 a.m. and measured an ozone concentration of a pproximately 95 ppb at about 600 meters, which is within the nocturn al low level jet. Another ozonesonde was

launched at 7:30 a.m. and measured an ozone concentration of a pproximately 90 ppb at about 1,000 meters (Figure 2-5). Each of th e ozone concentrations was observed at approximately the same height as the nocturn al temperature inversion as indicated by the kink in the temperature profile. The obser vations indicated that elevated ozone concentrations are within the nocturnal low level jet.The Nature of the Ozone Air Quality Problem in th e Northeast: A Conceptual Description Page 2-9



### Figure 2-5. Ozonesonde measurements on August 5, 2005 of elevated ozone concentrations in a nocturnal low level jet above Beltsville, MD



## 2.3.4. Upper level winds: Ozone and precursors aloft

Theoretical and numerical model simulations have suggested for some time that there is a strong regional component to urban air quality in the northeastern United States (Liu et al ., 1987; Sillman et al ., 1990; McKeen et al ., 1990). Since 1992, over 300 aircraft flights have been made to measure vertical profiles of ozone, the nitrogen oxides, carbon dioxide, sulfur dioxide, and more r ecently aerosol particles during high ozone episodes. d 

### Figure 2-6 shows the results of profiles taken over central Virginia on July 15, 1995, at about 9:00 am on the last day of a four day severe ozone episode. During this episode, winds measured at Sterling, Virg inia (IAD) in the 500-3000 m layer, where ozone was at a maximum, were consistently from the west to the north. This was particularly true on July 15. There were no periods of stagnation or reversal of wind direction during this period. Figure 2-6 shows that th e ozone mixing ratio above the boundary layer is much larger than that at the ground, peaking at about 1200 meters.

An examination of the various pollutant data in Figure 2-6 helps to identify possible sources of the elevated ozone. It s hould be noted that while both automobiles and power plants emit NO X 

### , automobiles emit carbon monoxide (CO) but not sulfur dioxide (SO 2 

### ), while power plants emit SO 2 

### but not CO. The CO profile is not correlated well with the ozone data, indica ting that the source of the oz one is not from local sources, i.e., automobiles. The peak in the NO Y e 

### profile at around 800 meters is an indication of “aged air” (hence transport) as a number of studies have found a strong relationship between increasing ozone and NO Y 

### in photochemically aged air masses (Trainer et al.

,

d These measurements were made as part of the University of Maryland’s RAMMPP (Regional Atmospheric Measurement, Modeling, and Prediction Program) under the sponsorship of ARMA, MARAMA (Mid-Atlantic Regional Air Management Association), VADEQ (Virginia Department of Environmental Quality), and NCDEQ (North Carolina Department of Environmental Quality).

e NO Y = NO + NO 2 + all other oxidized nitrogen products of NO X , excluding N 2 O. 

# 7:30AM 3:30AMThe Nature of the Ozone Air Quality Problem in the Northeast: A Conceptual Description Page 2-10



### 1993; Kleinman et al. , 1994; Olszyna et al. , 1994). Finally, the peak in the SO 2 

### profile, which occurs above the nocturnal inversion, is unlikely to come from local sources. Indeed the presence of the SO 2 

### leads to the conclusion that the air is coming from power plants west of the Appalachian Mountains.

Figure 2-6. Altitude profiles for ozone, carbon monoxide, NO Y 

### , and SO 2 

### taken on July 15, 1995

During the same July 1995 period, measurements aloft in other parts of the OTR also recorded high ozone overnight in layers 500 m or higher above the surface. Ozone aloft concentrations above Poughkeepsie, NY and New Haven, CT approached levels of 120 ppb or greater on the night of July 14 (Z hang & Rao, 1999). Figure 2-7 displays the aircraft measurements above Poughkeepsie, NY around 4 a.m. EST.The Nature of the Ozone Air Quality Problem in the Northeast: A Conceptual Description Page 2-11



### Figure 2-7. Observed vertical ozone prof ile measured above Poughkeepsie, NY at about 4 a.m. EST on July 14, 1995

0 20 40 60 80 100 120 140 

### Ozone (ppb) 1600

1200

800

400Altitude (meters) 

### 8-hour standard

Observed ozone

0 20 40 60 80 100 120 140 

### Ozone (ppb) 1600

1200

800

400Altitude (meters) 

### 8-hour standard

Observed ozone

Note: The figure includes a vertical line at 85 ppb for comparing aloft measurements with the 8-hour ozone NAAQS (observed ozone data from Zhang & Rao, 1999).



### The aircraft measurements since 1992 reinforce the previously mentioned observations by Clarke and Ching (1983) duri ng the summer of 1979, in which aircraft

measurements recorded aloft ozone concentr ations of about 90 ppb transported overnight from eastern Ohio and entering into the No rtheast Corridor over a region stretching from the lower Hudson River Valley north of New York City down across eastern Pennsylvania and into Maryland just west of Baltimore. The measurements also observed

NO X 

### aloft during the overnight hours that could contribute to additional ozone formation in the OTR as it mixed down to the surface in the morning.

The presence of high levels of ozone a nd precursors aloft across a large spatial region gives rise to the concept of an “ozone reservoir” existing at night just above the nocturnal inversion boundary. The pollutants in this reservoir are not subject to destruction at the surface, a nd can be transported long distan ces in the wind flows created by the synoptic scale weather patterns conduc ive to ozone formation and transport.



## 2.4. Atmospheric modeling of regional ozone transport

Modeling results by the USEPA for the Clean Air Interstate Rule (CAIR) further underscore the regional nature of ozone tr ansport into and with in the OTR through theThe Nature of the Ozone Air Quality Problem in the Northeast: A Conceptual Description Page 2-12



### various pathways described in the above sections. Based on ozone air quality modeling results, the USEPA tabulated the percent cont ribution to 8-hour ozone nonattainment in a

number of OTR counties. The USEPA modeled the contributions for the base year 2010, which included implementation of the NO X 

### SIP Call and other existing and promulgated control programs. Table 2-1 shows the CA IR results for the OTR counties (USEPA, 2005, from Table VI-2).

Table 2-1. USEPA CAIR modeling results of percent contribution to 8-hour ozone

nonattainment in OTR counties in 2010 due to transport from upwind states

2010 Base

Nonattainment

Counties 2010 Base 8-Hour Ozone (ppb) Percent of 8-Hour

Ozone due to

Transport

Fairfield CT 92 80 %

Middlesex CT 90 93 %

New Haven CT 91 95 %
Washington DC 85 38 %

Newcastle DE 85 37 %

Anne Arundel MD 88 45 %

Cecil MD 89 35 %

Harford MD 93 31 %

Kent MD 86 47 %
Bergen NJ 86 38 %

Camden NJ 91 57 %

Gloucester NJ 91 62 %

Hunterdon NJ 89 26 %

Mercer NJ 95 36 %

Middlesex NJ 92 62 %

Monmouth NJ 86 65 %

Morris NJ 86 63 %

Ocean NJ 100 82 %

Erie NY 87 37 %

Richmond NY 87 55 %

Suffolk NY 91 52 %

Westchester NY 85 56 %

Bucks PA 94 35 %

Chester PA 85 39 %
Montgomery PA 88 47 %
Philadelphia PA 90 55 %

Kent RI 86 88 %
Arlington VA 86 39 %

Fairfax VA 85 33 % From USEPA, 2005 (Table VI-2)



### The CAIR modeling by the USEPA also provides information on the upwind areas (by state) contributing to downwind nona ttainment in the OTR counties. Table 2-2 presents the upwind states significantly c ontributing to 8-hour ozone nonattainment in counties within the OTR, according to signi ficance criteria used by the USEPA (USEPA, 2005, from Table VI-5). The states listed in the table as significantly contributing toThe Nature of the Ozone Air Quality Problem in the Northeast: A Conceptual Description Page 2-13



### downwind ozone nonattainment in the OTR coun ties include states outside of the OTR, indicating the broad regional scale of the ozone transport problem.

Table 2-2. USEPA CAIR modeling results of upwind states that make a significant

contribution to 8-hour ozone in downwind OTR nonattainment counties

Downwind State/County Upwind States

CT Middlesex MA NJ NY OH PA VA

CT New Haven MD/DC NJ NY OH PA VA WV

CT Fairfield MD/DC NJ NY OH PA VA WV

District of Columbia MD/DC OH PA VA

DE New Castle MD/DC MI NC OH PA VA WV

MD Harford NC OH PA VA WV

MD Kent MI NC OH PA VA WV

MD Cecil MI OH PA VA WV

MD Anne Arundel MI NC OH PA VA WV

NJ Ocean DE MD/DC MI NY OH PA VA WV
NJ Bergen MD/DC MI OH PA VA WV

NJ Gloucester DE MD/DC MI OH PA VA WV

NJ Morris DE MD/DC MI NY OH PA VA WV

NJ Middlesex DE MD/DC MI NY OH PA VA WV

NJ Hunterdon DE MD/DC OH PA VA WV

NJ Camden DE MD/DC MI OH PA VA WV

NJ Mercer DE MD/DC MI NY OH PA VA WV

NJ Monmouth DE MD/DC MI NY OH PA VA WV

NY Erie MD/DC MI NJ PA VA WI

NY Westchester MD/DC NJ OH PA VA WV

NY Richmond MD/DC MI NJ PA VA WV

NY Suffolk CT DE MD/DC MI NC NJ OH PA VA WV
PA Montgomery DE MD/DC NJ OH WV
PA Philadelphia DE MD/DC MI NJ OH VA WV

PA Chester DE MD/DC MI NJ OH VA WV

PA Bucks DE MD/DC MI NJ OH VA WV

RI Kent CT MA NJ NY OH PA VA
VA Arlington MD/DC OH PA

VA Fairfax MD/DC OH PA WV From USEPA, 2005 (Table VI-5). States are listed alphabetically and not according to order of influence.



### While the USEPA modeled 40 eastern U.S. counties as in nonattainment of the 8- hour ozone NAAQS in the 2010 base year (including counties not in the OTR), it projected that only three of those 40 countie s would come into attainment by 2010 with

the additional NO X 

### reductions of CAIR (USEPA, 2005, p. 58). The USEPA modeling does predict that ozone will be lower in the remaining nonattainment counties by 2010 due to CAIR, with additional counties co ming into attainment by 2015. The CAIR reductions, therefore, will bring the OTR nona ttainment counties closer to attainment by 2010, but will not result in attainment for a la rge majority of OTR counties predicted to be in nonattainment in 2010 prior to implementation of CAIR.The Nature of the Ozone Air Quality Problem in the Northeast: A Conceptual Description Page 2-14



## 2.5. Summary

This section has summarized current know ledge of the meteorological processes

that affect local ozone levels within the OTR. A conceptual description of transport within the OTR can be divided into three pr inciple components: ground level transport at the surface, transport by the nocturnal low leve l jet, and transport aloft. All three modes of transport depend on the loca tion of the high pressure system. Ground level transport is

the result of inte raction between the synoptic flow a nd local effects, such as the sea breeze and the Appalachian lee side trough. Tr ansport within the OTR can occur by the nocturnal low level jet that forms late at ni ght or in the very early morning hours. This phenomenon is a result of the differential heating of the air between the Appalachian

Mountains and the Atlantic O cean. It has been observed throughout the Eastern Seaboard from Georgia to Maine. The nocturnal low level jet can transport ozone that formed within the OTR or was transported into the OTR from outside the region. Transport aloft is dominated by the anti-cyclonic flow around a high pressure system, which can lead to transport of an ozone reservoir into the OTR created by emissions in areas that lie outside

the OTR. Local emissions within the OTR add to the polluted air mixing down from

above that arrived from more distant locations.

Atmospheric modeling by the USEPA underscores the observations that the OTR’s ozone problem has contributions from outside and upwind of the region. Pollution sources in the Ohio River Valley and the Southeast significantly contribute to ozone nonattainment problems in vari ous portions of the OTR.The Nature of the Ozone Air Quality Problem in the Northeast: A Conceptual Description Page 2-15



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1990.

Woodman, M.F., D.T. Nguyen, D.J. Krask, E. Joseph, V. Davis, R. Hoff, R. Rogers, M.G. Seybold. “Maryland Ozonesonde Camp aign 2005.” Poster at EPA National Air Quality Conference, San Antonio, TX, 2006.

Zhang J. and S.T. Rao. “The role of verti cal mixing in the tempor al evolution of groundlevel ozone concentrations.” J. Applied Meteor. 38 , 1674-1691, 1999.The Nature of the Ozone Air Quality Problem in th e Northeast: A Conceptual Description Page 3-1



# 3. OZONE-FORMING POLLUTANT EMISSIONS

The pollutants that affect ozone fo rmation are volatile organic compounds (VOCs) and nitrogen oxides (NO X 

### ). The emissions dataset presented for the OTR in the

first section below is from the 2002 MANE -VU (Mid-Atlantic/Northeast Visibility Union) Version 2 regional haze emissions i nventory. MANE-VU is the regional planning organization (RPO) for the mid-Atlantic and Northeast states coordinating regional haze planning activities for the region. While the context of the MANE-VU inventory is regional haze, it include s inventories of NO X 

### and VOCs that also inform air quality planners on sources important to ozone formation. f 

### To provide a fuller context of precursor emissions contribu ting to regional ozone affec ting the OTR, the section following the MANE-VU information presents NO X 

### and VOC emissions information from the 2002 National Emissions Inventory (NEI) for states in adjacent RPOs.



## 3.1. Emissions inventory characteristics in the OTR

3.1.1. Volatile organic compounds (VOCs)

Existing emission inventories generally refer to VOCs as hydrocarbons whose volatility in the atmosphere makes them pa rticularly important in enhancing ozone formation in the presence of NO X



### . As shown in Figure 3-1, the VOC inventory for the OTR is dominated by mobile

and area sources. Most VOC emissions in the OTR, however, come from natural sources, which are not shown in the figure. Among the human-caused VOC emissions, on-road

mobile sources of VOCs include exhaust emi ssions from gasoline passenger vehicles and diesel-powered heavy-duty vehicles as well as evaporative emissions from transportation fuels. VOC emissions may also originate from a variety of area sources (including solvents, architectural coatings, and dry cl eaners) as well as from some point sources (e.g., industrial f acilities and petrol eum refineries).

Naturally occurring (biogenic) VOC em issions are caused by the release of natural organic compounds from plants in warm weather. Many natural VOCs that contribute to ozone formation are highly re active. Isoprene, for example, is a highly

reactive five-carbon natural VOC emitted from mostly deciduous trees (e.g., oaks) that plays an important role in enhancing regi onal ozone formation across the eastern U.S. (Trainer et al. , 1987; Chameides et al. , 1988). Because biogenic VOC emissions are large and reactive, they are the most important pa rt of the VOC inventory for understanding and predicting ozone formation. Biogenic VOC s are not included in Figure 3-1, but nationally, they represent roughly two-thir ds of all annual VOC emissions (USEPA, 2006a). Modeling biogenic emissions can be diffi cult as it requires simulating biological responses to a range of environmental condi tions, such as leaf temperature and the amount of sunlight r eaching a leaf surface.

f The description of OTR state inventories discussed in the first section does not include the portion of Virginia in the Washington, DC metropolitan area. Information for Virginia is in the following section and comes from the 2002 National Emissions Inventory.The Nature of the Ozone Air Quality Problem in th e Northeast: A Conceptual Description Page 3-2



### Figure 3-1. 2002 MANE-VU state VOC inventories in the OTR

0% 25% 50% 75% 100%

Connecticut

De

l a wa

re

District of

Columbia Maine Ma ry

lan

d
Mass a ch

u s e t ts

Ne

w

Ha

m

ps

h i re New Jersey
Ne

w

Yo

rk

P

e nnsylvania

Rh

o de I s land Ve rmo n tmillion t/y

0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6

AREA NONROAD ONROAD POINT Emission

Figure key: Bars = Percentage fractions of four source categories; Circles = Annual

emissions amount in 10 6 tons per year. The Virginia portion of the Washington, DC metropolitan area is not shown in the figure.



## 3.1.2. Oxides of nitrogen (NO X 

## )

NO X 

### emissions are a fundamental necessity for the atmospheric formation of

ozone. Without NO X 

### , ozone formation during warm su mmer days would virtually cease, regardless of the amount of reactive VOCs present. By contrast, without VOCs, NO X 

### would still produce ozone in the presence of sunlight, albeit at a much diminished efficiency.

Figure 3-2 shows NO X 

### emissions in the OTR at the state level. Since 1980,

nationwide emissions of NO X 

### from all sources have s hown little change. In fact, emissions increased by 2 percent betw een 1989 and 1998 (USEPA, 2000). This increase is most likely due to industrial sources a nd the transportation sector, as power plant combustion sources have implemented modest emissions reductions during the same time period. Most states in the OTR experienced declining NO X 

### emissions from 1996 through 2002, except Massachusetts, Maryland, New York, and Rhode Island, which show an

increase in NO X 

### emissions in 1999 before declining to levels below 1996 emissions in

2002.The Nature of the Ozone Air Quality Problem in th e Northeast: A Conceptual Description Page 3-3



### Figure 3-2. State level ni trogen oxides emissions

0.0 0.2 0.4 0.6 0.8 1.0 1.2

Co

n ne

c t i cu

t Delaware District of C

olu

m bia M aine

M

a ry

land

Mas s ach u setts

Ne

w Ha m

p s hi

re New Jersey

Ne

w Yor k

P

e nn

s y l v a n i a Rhode I s l an

d

V

e rm

o ntmillion t/y NEI 1996

NEI 1999

MV 2002 v.2



### Monitored ambient NO X 

### trends during the summer from 1997 to 2005 corroborate

the downward trend in NO X 

### emissions seen in the emissions inventories for the OTR. As seen in Figure 3-3, the 24-hour (lower trend lines) and 6 a.m.-8 a.m. (upper trend lines)

NO X 

### concentrations indi cate decreases in NO X 

### over this time period in the OTR. The

NO X 

### reductions likely come from decreasing vehicle NO X 

### emissions due to more stringent motor vehicle standards as well as NO X 

### reductions from the OTR NO X 

### Budget Program and the NO X 

### SIP Call (mainly power plants).The Nature of the Ozone Air Quality Problem in th e Northeast: A Conceptual Description Page 3-4



### Figure 3-3. Plot of monitored NO X 

### trends in OTR during 1997-2005

JUNE, JULY & AUGUST 1997-2005 OTC AVERAGE NOx CONCENTRATIONS

10 15 20 25 30 35 40 45 50199719981999200020012002200320042005199719981999200020012002200320042005199719981999200020012002200320042005Average Concentration (ppb) .

JUN (all hrs)

JUL (all hrs)

AUG (all hrs)

JUN (06-08 EST)

JUL (06-08 EST)

AUG (06-08 EST)

Note: Upper trend lines correspond to ambient NO X measured from 0600-0800 EST in the morning. Lower trend lines correspond to NO X measured over entire day (created by Tom Downs, Maine Department of Environmental Protection).



### Power plants and mobile sources ge nerally dominate state and national NO X 

### emissions inventories. Nationally, power plants account for more than one-quarter of all

NO X 

### emissions, amounting to over six million tons. The electric sector plays an even larger role, however, in parts of the industrial Midwest where high NO X 

### emissions have a particularly significant power plant contribu tion. By contrast, mobile sources dominate

the NO X 

### inventories for more urbanized mid-Atla ntic and New England states to a far greater extent, as shown in Figure 3-4. In these states, on-road mobile sources — a category that mainly includes highway vehi cles — represent the most significant NO X 

### source category. Emissions from non-road (i .e., off-highway) mobile sources, primarily diesel-fired engines, also represent a substantial fraction of the inventory.The Nature of the Ozone Air Quality Problem in th e Northeast: A Conceptual Description Page 3-5



### Figure 3-4. 2002 MANE-VU state NO X 

### inventories in the OTR

0% 25% 50% 75% 100%

C

o nnec t i c ut

D

elaware

Di

s t ri ct of C

ol

umbi a Mai ne

M

ar

y land

M

as

sac

hus etts New Hampshi r e

N

e w

Jers ey

Ne

w York

Pennsylvania

R

hode I s land Vermontmillion t/y

0.0 0.3 0.6 0.9

AREA NONROAD ONROAD POINT Emission

Figure key: Bars = Percentage fractions of four source categories; Circles = Annual

emissions amount in 10 6 tons per year. The Virginia portion of the Washington, DC metropolitan area is not shown in the figure.



## 3.2. Emissions inventory characteristics outside the OTR

NO X 

### and VOC emissions in the OTR are only one component of the emissions contributing to ozone affecting the OTR. As regional modeling for the NO X 

### SIP Call and CAIR have shown, emission sources, primarily of NO X 

### , located outside the OTR can significantly contribute to ozone transported into the OTR. Here we present regional emissions information grouped by the thre e eastern RPOs – MANE-VU, VISTAS (Visibility Improvement State and Tribal A ssociation of the Southeast), and the MWRPO (Midwest RPO). Table 3-1 lists the states in each RPO.

The inventory information is extrac ted from the USEPA final 2002 National Emissions Inventory (NEI). For consistency, the MANE-VU information here also comes from the 2002 NEI rather than from the MANE-VU Version 2 regional haze emissions inventory described above. The differences be tween the inventories are not great, as the NEI and the MANE-VU Version 2 inventory are both based on the same inventory information provided by the states.The Nature of the Ozone Air Quality Problem in th e Northeast: A Conceptual Description Page 3-6



### Table 3-1. Eastern U.S. RPOs and their state members

RPO State

MWRPO Illinois

MWRPO Indiana MWRPO Michigan

MWRPO Ohio

MWRPO Wisconsin

MANE-VU Connecticut

MANE-VU Delaware

MANE-VU District of Columbia

MANE-VU Maine MANE-VU Maryland

MANE-VU Massachusetts MANE-VU New Hampshire MANE-VU New Jersey

MANE-VU New York MANE-VU Pennsylvania

MANE-VU Rhode Island

MANE-VU Vermont

VISTAS Alabama

VISTAS Florida VISTAS Georgia VISTAS Kentucky VISTAS Mississippi

VISTAS North Carolina

VISTAS South Carolina

VISTAS Tennessee VISTAS Virginia VISTAS West Virginia

Table 3-2 presents VOC emissions by source sector and RPO for the eastern

United States. The NO X 

### emissions by source sector and RP O are presented in Table 3-3. Regionally, NO X 

### emissions are more important with respect to regional ozone formation and transport. NO X 

### emissions in combination with abundant naturally occurring VOC emissions from oaks and other vegetation have been shown to be important sources of regional ozone in the eastern U.S. (Trainer et al. 1987; Chameides et al. 1988).

Table 3-2. VOC emissions in eastern RPOs

RPO Point Area On-road Non-road Total
MWRPO 234,938 1,182,186 660,010 492,027 2,569,160
MANE-VU 93,691 1,798,158 793,541 494,115 3,179,504
VISTAS 458,740 2,047,359 1,314,979 609,539 4,430,617The Nature of the Ozone Air Quality Problem in th e Northeast: A Conceptual Description Page 3-7



### Table 3-3. NO X 

### emissions in eastern RPOs

RPO Point Area On-road Non-road Total
MWRPO 1,437,284 184,790 1,290,178 723,844 3,636,096
MANE-VU 680,975 268,997 1,297,357 534,454 2,781,783
VISTAS 2,094,228 266,848 2,160,601 812,615 5,334,293



## 3.3. Are NO X 

## or VOC control strategies most effective at reducing

ozone?

The effectiveness of a NO X 

### -focused or VOC-focused control strategy to reduce ozone is not constant by location or emi ssions; rather it is a changing chemical characteristic of an air parcel affecting a part icular location. As a result, the effectiveness

of a NO X 

### or VOC-focused control st rategy can vary within an air parcel as it dynamically evolves over time with transport, dispersi on, and photochemical aging (NARSTO, 2000).

On a regional basis, OTAG, CAIR and ot her modeling studies have consistently

shown that NO X 

### reductions have the greatest impact on regional ozone concentrations, while VOC reductions have more local impact s. This is largely a result of significant naturally occurring VOC emissions (especially is oprene) in large forested regions of the eastern U.S. Real-world results from regional NO X 

### reductions at power plants (i.e., the

NO X 

### SIP Call) are now indicati ng that significant ozone re ductions are occurring on a regional basis as a result of regional NO X 

### strategies. A recent USEPA report finds a strong association between areas with the greatest NO X 

### emission reductions due to the

NO X 

### SIP Call and downwind sites exhibiting th e greatest improvement in ozone in 2005 (USEPA, 2006b).

As a general rule, VOC reductions may be effective at reducing urban-scale ozone pollution in lieu of or in combination with local NO X 

### reductions, while regional NO X 

### controls are most effective at reducing re gional ozone. While a general rule can be outlined in evaluating the potential effectiveness of NO X 

### and VOC-focused control strategies, the optimal strategy for a specific location will depend on the particular circumstances of that location. Exceptions to a VOC-only strategy fo r an urban area can

occur when the urban area has large natural VOC emissions, ozone is transported from upwind, or there is recirculation of aged local pollution (e.g., sea breeze effect). Furthermore, because the conditions causing individual ozone episodes can vary, a given urban area may change in sensitivity between a NO X 

### and VOC-focused strategy depending on a particular episode’s cond itions (NARSTO, 2000). Therefore, the appropriate combination of VOC and NO X 

### controls at the local level depends on local circumstances with the realization that a single approach focusing on NO X 

### or VOC-only controls is not necessarily effective for all episode types. It is clear, however, that regional NO X 

### reductions provide regional ozone reduc tions, and this will influence ozone levels being transported into local urban areas.The Nature of the Ozone Air Quality Problem in th e Northeast: A Conceptual Description Page 3-8



## 3.4. Summary

There are large emissions of VOCs and NO X 

### within and outside the OTR that contribute to local and regiona l ozone problems. Naturally occurring VOC emissions play an important role in combination with human-caused NO X 

### emissions in forming regional ozone across large sections of the eastern U.S. Regional NO X 

### control strategies are demonstrating success in reducing regional ozone. On a more local scale, some

combination of VOC and NO X 

### controls may be needed, with the specific combination dependent upon local circumstances.The Nature of the Ozone Air Quality Problem in th e Northeast: A Conceptual Description Page 3-9



## References

Chameides, W.L., R.W. Lindsay, J. Richardson, and C.S. Kiang. “The role of biogenic hydrocarbons in urban photochemical smog: Atlanta as a case study.” Science 241 , 1473- 1475, 1988.

NARSTO. An Assessment of Tropospheric Ozone Pollution . NARSTO, July 2000.

Trainer, M., E.J. Williams, D.D. Parrish, M.P. Buhr, E.J. Allwine, H.H. Westberg, F.C. Fehsenfeld, and S.C. Liu. “Models and observations of the impact of natural hydrocarbons on rural ozone.” Nature 329 , 705-707, 1987.

USEPA. National Air Quality and Emission Trends Report, 1998 , EPA 454/R-00-003,

available online: http://www.epa.gov/oar/aqtrnd98/ , 2000.

USEPA. 2002 Final National Emissions Inventory (NEI) , available online: ftp://ftp.epa.gov/EmisInventory/2002finalnei/ , 2006a (accessed October 10, 2006) [The 2002 NEI reports national annual emissions fo r total anthropogenic VOC emissions as 16.8 million tons, and total biogenic VOC emissions as 41.8 million tons].

USEPA. NO X 

### Budget Trading Program 2005 Compli ance and Environmental Results

, EPA430-R-06-013, available online: http://www.epa.gov/airmarkets/fednox/ , 2006b.The Nature of the Ozone Air Quality Problem in th e Northeast: A Conceptual Description Page 4-1



# 4. WHAT WILL IT TAKE TO CLEAN THE AIR?

– LINKING THE SCIENCE TO POLICY

4.1. The three phases of a bad ozone day and the ozone reservoir

With the atmospheric chemistry, me teorology, and air emission inventory elements presented in the previous sections , a conceptual descript ion emerges of ozone problem in the OTR. Consider a typical “day,” defined as starting at sunset, for a severe ozone event associated with a high pressure system. Conceptually, a bad ozone day can be considered as occurring in three phases. During phase one, a nocturnal inversion forms as the temperature of the earth drops followi ng sunset, isolating the surface from stronger winds only a few hundred feet overhead. Ozone near the surface cannot mix with ozone above and is destroyed as it reacts with the Earth’s surface. In a city, fresh NO X 

### emissions react with ozone, further reducing it s concentration, so that by morning, very

little ozone is left below the nocturnal inversion. At this time, the nocturnal inversion is at its strongest, and winds at the surface are typically calm.

Above the nocturnal inversion, the situ ation is quite different. Ozone and its precursors, both from the previous day’s lo cal emissions and from transport, remain largely intact. There are no surfaces to react w ith the ozone and a large reservoir of ozone remains above the inversion. During phase two of a bad ozone day, the nocturnal inversion breaks down at mid-morning, with the result that the ozone and precursors

above the inversion can now mix with the air near the surface. The result of this mixing is a sudden change in ozone. Figure 4-1 show s median ozone profiles for morning and afternoon aircraft flights from 1996 – 2003. One can clearly see the breakdown of the nocturnal inversion throughout the day (Hudson, 2005).

Figure 4-1. Median ozone profiles for morning and afternoon flights

from 1996 – 2003

O 3 median profiles for morning and afternoon flights
(1996 - 2003)

0 500 1000 1500 2000 2500 3000 3500

0 20 40 60 80 100 120

Median O 3 (ppb) with 25 th and 75 th percentilesPressure derived altitude (m) median am (254)

median pm (293) q25 am

q75 am

q25 pm

q75 pm AM PMThe Nature of the Ozone Air Quality Problem in th e Northeast: A Conceptual Description Page 4-2



### In phase three of a bad ozone day, ozone concentrations reach their highest levels in the afternoon through the combined accumula tion of local pollution produced that day mixed with the transported regional polluti on load brought in overnight from the ozone reservoir. Figure 4-2 shows this graphically for the southern OTR. The ozone monitor at Methodist Hill, PA is a high elevation site lo cated at 1900 ft in alt itude in south central Pennsylvania, and is above the nocturnal inve rsion. In the early morning hours of August 12, 2002 (e.g., 5 a.m.), it recorded ozone c oncentrations above 80 ppb, which was much higher than what other lower elevation monitors in the region were recording (e.g., Little Buffalo State Park, PA, South Carroll Count y, MD, Frederick, MD, Ashburn, VA, Long Park, VA). Due to the lack of sunlight necessary to produce ozone photochemically during nighttime hours, the high ozone levels seen at Methodist Hill, PA indicate the presence of a significant ozone reservoir above the nocturnal inversion layer produced during daylight hours at some earlier point in time and transp orted into the region. With the break up of the nocturnal inversion after sunrise (e.g., starting about 7 a.m.), ozone

concentrations at the lower el evation monitors show a rapid increase. This reflects the mixing down of the ozone reservoir from highe r altitude to the surface in combination with local ozone production near the surf ace now that the sun has begun inducing its photochemical production.

Figure 4-2. Hourly ozone profiles in the southern OTR, August 12, 2002

0 20 40 60 80 100 120 1400:001:002:003:004:005:006:007:008:009:0010:0011:0012:0013:0014:0015:0016:0017:0018:0019:0020:0021:0022:0023:00

Hour (EST)Ozone (ppb) South Carroll, MD

Frederick, MD

Methodist Hill, PA

Little Buffalo SP, PA

Ashburn, VA

Long Park, VA



### The ozone reservoir extends across the OT R, as seen on the same night in high elevation ozone monitoring sites in the north ern OTR. Figure 4-3 shows the hourly ozone concentrations measured on August 12, 2002 at Mohawk Mountain, CT, Cadillac Mountain, ME, Mt. Greylock, MA, Mt. M onadanock, NH, Mt. Washington, NH, andThe Nature of the Ozone Air Quality Problem in th e Northeast: A Conceptual Description Page 4-3



### Whiteface Mountain, NY. As with Methodist Hill, PA on this day, these sites show elevated ozone concentrations during nighttime hours, as compared to lower elevation sites below the nocturnal inversion (e.g., Danbury, CT). By mid-day, however, the nocturnal boundary layer has broken down, mixing the transported ozone from the reservoir above into the locally produced ozone below. Appendix G provides more detail

on contributions to the ozone reserv oir within and outside the OTR.

Figure 4-3. Hourly ozone profiles in the northern OTR, August 12, 2002

0 20 40 60 80 100 120 1400:001:002:003:004:005:006:007:008:009:0010:0011:0012:0013:0014:0015:0016:0017:0018:0019:0020:0021:0022:0023:00

Hour (EST)Ozone (ppb)

Mohawk Mtn., CT

Mt. Monadanock, NH

Mt. Greylock, MA

Mt. Washington, NH

Whiteface Mtn., NY

Cadillac Mtn., ME

Danbury, CT

Data provided by Tom Downs, Maine De partment of Environmental Protection.



## 4.2. Chronology of an ozone episode – August 2002

The chronology of an historical ozone ep isode occurring in the OTR from August 8 to August 16, 2002 provides a real-world exam ple that pieces together the elements of the ozone conceptual description given in this document. Surface maps from the period provide a synoptic overview of major weather systems that were influencing air quality across the OTR during that time. Meteor ological insights combined with ozone concentration information provide a picture of the evolving ozone episode on a day-byday basis. Figure 4-4, Figure 4-5, and Figure 4- 6, respectively, show eight-panel displays of surface weather maps, back trajectories, and 8-hour maximum ozone concentrations from each day. The daily progression shows th e formation of high ozone that shifts from west to east, and ultimately northward, during successive days of the episode according to local ozone formation and transport shaped by wind patterns within and outside of the

OTR.

The August 2002 episode began with a slow-moving high pressure system

centered over the Great Lakes in itiating a northerly flow over the OTR on August 8. OverThe Nature of the Ozone Air Quality Problem in th e Northeast: A Conceptual Description Page 4-4



### the next several days, the high drifted sout heastward and became extended across a large part of the eastern U.S., bringing high temper atures to the region. Calm conditions west of the OTR on August 10 were pivotal for th e formation of ozone, which first began building in the Ohio River Valley. Over the next four days, 8-hour ozone concentrations climbed well above the 85 ppb (0.08 ppm) NAA QS over a wide area of the OTR. Large parts of the heavily populated Northeast Corridor experien ced 8-hour ozone levels above 100 ppb during the height of the episode , which far exceeded the 85 ppb NAAQS.

The following chronology provides a da y-by-day evolution of the August 2002 ozone episode. Parts of this desc ription are taken from Ryan (2003).

August 8: A high pressure system over the Great Lakes produces NW-N prevailing surface winds (~4-8 mph) throughout the region. Maximum daily temperatures approach or exceed 80o F.

August 9: Wind speeds fall off but the direction remains NW-N as the high moves into the Pennsylvania-New York regi on. Temperatures rise as cloud cover declines. Background ozone levels begin to bu ild in the Ohio Rive r Valley with 8-hour maximum concentrations reaching the 60-80 ppb range.

August 10: High pressure is directly over the mid-Atlantic. With dew points still in the mid-50o’s F, the skies are extraordin arily clear throughout th e day. Temperatures (except in northern-most areas) approach 90o F while surface-level winds turn to more southerly directions. With high pressure overhea d, the back trajectories suggest very light

winds and recirculation. Calm conditions th rough the morning hours in the lower Ohio River Valley promote increasingly higher levels of ozone noted in surface observations – now reaching above the 85 ppb 8-hour ozone NAAQS over much of Indiana, Ohio, and other states along the Ohio River, as well as states around Lake Michigan and large portions of the southeastern U.S. Ozone levels above the 8-hour NAAQS now begin appearing for the first time in the west ern and southern parts of the OTR.

August 11: Surface high pressure drops slow ly southeastward across the midAtlantic with the center in western North Carolina drifting to coastal South Carolina during the day. The upper level ridge has al so moved east and is located over the midAtlantic. Circulation around the high becomes well established. A surface-level trough

descends from north of the Great Lakes duri ng the day, passes eas tward through the Ohio River Valley and stalls over the Allegheny Mo untains and southward. Peak temperatures are in the low to mid-90o’s F. Morning winds are low-to-calm in the area east of the Mississippi – the area of ozone now reaches from eastern Wisconsin to Tennessee and eastward to Georgia up through the Carolin as into the OTR, covering most of Pennsylvania, New York, New Jersey, Conn ecticut, Rhode Island and Massachusetts. Winds are generally south to southwest as is reflected in the boundary layer back trajectories. The key factor driving local ozone production ap pears to be a very stable boundary layer. The 8 a.m. sounding at the Washington-Dulles airport shows a very strong low-level inversion from 950-900 mb with a deep residual layer beneath a continuing strong subsidence inversion – now based at 760 mb.

August 12: The upper level ridge remains quasi-stationary with its axis over the

mid-Atlantic. The center of hi gh pressure at 850 mb is over North Carolina and Georgia. At the surface, the characteristic Appalachia n lee side trough forms. Temperatures exceedThe Nature of the Ozone Air Quality Problem in th e Northeast: A Conceptual Description Page 4-5



### 90o F throughout the OTR except in coastal Ma ine. Winds are fairly strong from the northwest. This is reflected in the back trajectories that show a shift to westerly transport. Elevated upwind ozone concentrations at 11 a.m. on August 11 occur in the vicinity of the origin of the back traject ories, on the order of 78-86 ppb. Ozone concentrations fall this day west of the Appalachians but increase markedly across the mid-Atlantic. The area of highest ozone has pushed eastward and now extends from southern Maine across central Pennsylvania down through Maryland in to the Carolinas, Georgia, and eastern Tennessee. Ozone builds throughout the day as ci rculation forces it to channel northeast between the stalled trough and a cold front a pproaching from the Midwest. Some of the highest 8-hour concentrations occur through th e central to southern OTR on this day.

August 13: Calm conditions prevail as the trough reaches coastal New Jersey by 8 a.m. Generally clear skies allow temperat ures to reach the mid-90o’s F everywhere except in coastal Maine. Dew points, which had been rising since August 8, reach the upper 60o’s F. A morning sounding at the Washington-Dulles airport showed a continuing strong low level inversion with a residual mixed layer to 850 mb ending just beneath a weak secondary inversion. The cap aloft has lifted to ~ 630 mb and the sounding is more unstable compared to previ ous day’s between the two inversion layers. The Appalachian lee side trough continues in place from late on August 12. As is typically the case, the highest ozone concentrations are found in proximity to this boundary. The highest 8-hour ozone concentratio ns are along the eastern portions of the OTR from northeastern Virginia through New Jersey, Long Island, Connecticut, and into eastern Massachusetts. By 8 p.m., showers a ssociated with the approaching cold front

have reached into Ohio.

August 14: By 8 a.m., the trough has dissipated and the high is moving offshore, resulting in an increasing southerly wi nd component, which pushes maritime air northward. Dew points remain in the upper 60o’ s F and peak temperatures reach into the 90o’s F everywhere and top 100o F in several locations. Ozone concentrations build again, with the highest levels concentrated in the central OTR from eastern Pennsylvania across to Massachusetts. A “hotspot” of ozone appears in upstate New York at the eastern end of Lake Ontario, and may be the result of tran sport from the west across the lake. Ozone

concentrations decrease south and west of Baltimore and along coastal New Jersey as cleaner maritime air pushes in from the south.

August 15: This episode ends in a very diffe rent manner than the standard high ozone episode. Instead of the passage of a shar p cold front, this episode ends gradually as cleaner air sweeps north, winds increase, and the atmosphere steadily destabilizes. Ozone

concentrations fall across the middle and lo wer OTR as low level flow becomes more southeast and the Bermuda high fills in west ward. The highest levels, still exceeding the 8-hour ozone NAAQS, now occur in the north ern reaches of the OTR in upstate New York, Vermont, New Hampshire, and Maine.

August 16: Cloud cover spreads over the region with ozone falling further. The new high building into the upper Midwest pushe s the remains of the showers out of the Northeast. A spot of high ozone persists in central New Jersey. This is the last exceedance day in a string of seven exceed ance days within the OTR during this extended episode.The Nature of the Ozone Air Quality Problem in th e Northeast: A Conceptual Description Page 4-6



### Figure 4-4. Surface weather maps for August 9-16, 2002

August 9, 8:00AM EDT August 10, 8:00 AM EDT

August 11, 8:00 AM EDT August 12, 8:00 AM EDT

August 13, 8:00 AM EDT August 14, 8:00 AM EDT

August 15, 8:00 AM EDT August 16, 8:00 AM EDTThe Nature of the Ozone Air Quality Problem in th e Northeast: A Conceptual Description Page 4-7



### Figure 4-5. HYSPLIT 72-hour back trajectories for August 9-16, 2002

Aug 9, 2002 8 am EDT 

### Aug 10, 2002 8 am EDT



### Aug 11, 2002 8 am EDT Aug 12, 2002 8 am EDT

Aug 13, 2002 8 am EDT Aug 14, 2002 8 am EDT

Aug 15, 2002 8 am EDT Aug 16, 2002 8 am EDTThe Nature of the Ozone Air Quality Problem in the Northeast: A Conceptual DescriptionPage 4-8Figure 4-6. Spatially interpolated maps of maximum 8-hour surface ozone concentrations August 9 – 16, 2002The Nature of the Ozone Air Quality Problem in th e Northeast: A Conceptual Description Page 4-9



## 4.3. Clean Air Act provisions

As is evident from the myriad source re gions and transport pathways affecting the OTR, the regional ozone nonattainment problem presents a significant challenge to air quality planners. To improve air quality, emi ssion reductions of the appropriate pollutants must occur at the appropriate levels (i.e., st ringency of controls) a nd over the appropriate geographic extent. States have primary respons ibility for achieving the goals of the Clean Air Act, as they are responsible for developing State Implementation Plans and implementing and enforcing emission reduction programs to meet th e health-protective National Ambient Air Quality Standards (NAAQS).

When Congress passed the Clean Air Act Amendments of 1990, it recognized that air pollution transcends politic al boundaries and that tools for addressing transport must be made available to state and federal govern ments. Accordingly, several Clean Air Act provisions deal with tr ansported pollution, including: (1) prohib iting the USEPA from approving State Implementation Plans that interf ere with another state’s ability to attain or maintain a NAAQS; (2) requiring the USEPA to work with states to prevent emissions that contribute to air pollution in a forei gn country; (3) allowing states to form ozone transport regions; (4) requiring states in ozone transport regions to adopt a prescribed set

of controls in order to achieve a minimum level of regional emission reductions; and (5) allowing states to petition the USEPA for timel y relief from stationary source emissions

that interfere with at tainment or maintenance of a NAAQ S, and requiring the USEPA to act on such petitions within a very short, prescribed timeframe. Taken together, these provisions provide a framework for air quality planning. Its inherent principles are:

• Timely action is critical in order to protect public health;

• States must act locally to address air pollution;

• While acting locally, states must also cons ider their impacts downwind in addition to in-state impacts when developing state implementation plans (SIPs), and ameliorate such impacts through SIPs;

• Regional actions have been and can continue to be effective;

• To be effective on a regional level, states working together must work off of a level playing field.

What the science tells us of the nature of the ozone problem in the OTR supports this framework. The smaller scale weather pa tterns that affect po llution accumulation and transport underscore the importance of local (in-state) controls for NO X 

### and VOC emissions. Larger synoptic scale weather patt erns, and pollution patterns associated with them, support the need for NO X 

### controls across the eastern United States. Studies and

characterizations of nocturnal low level jets (i.e., channele d transport) also support the need for local and regional controls on NO X 

### and VOC sources as local and transported pollution from outside the OTR can be entrai ned in nocturnal low level jets formed during nighttime hours within the OTR. Land, sea, mountain, and valley breezes indicate that there are unique aspects of pollution accumulation and tran sport that are area-specific and will warrant policy responses at the loca l and regional levels beyond a one-size-fitsall approach.The Nature of the Ozone Air Quality Problem in the Northeast: A Conceptual Description Page 4-10



### The mix of emission controls is also impor tant for states to consider. While longrange transport of ozone is primarily due to NO X 

### , VOCs are important because they contribute to ozone formation by influenci ng how efficiently ozone is produced by NO X 

### , particularly within urban centers. While re ductions in anthropogenic VOCs will typically have less of an impact on the long-range tran sport of ozone, they can be effective in reducing ozone in those urban areas wher e ozone production may be limited by the availability of VOCs. Therefore, a combin ation of localized VOC reductions in urban

centers with additional NO X 

### reductions (from both mobile and point sources) across a larger region will help to reduce ozone and precursors in nonattainment areas as well as their downwind transport across th e entire region (NESCAUM, 1997).



## 4.4. Past regional efforts

While states are somewhat limited in thei r ability to directly affect emissions reductions beyond their own geo- political boundaries, over th e past 15-20 years, the Northeast states have acted regionally w ith tremendous success. Such efforts have

included:

• In 1989, regional low volatility gasoline (i.e ., Reid Vapor Pressure pf 9.0 psi) was introduced into the NESCAUM region, re sulting in significant VOC reductions;

• In 1994, the California Low Emission Vehi cle (LEV) program commenced in the Northeast Corridor as regulations were adopted by Maine, Massachusetts, New York, and Vermont. To date, four additional states have joined the program, which continues to yield reductions in NO X 

### , VOC, CO, and air toxics.

• In 1994, the states of the Ozone Tran sport Commission agreed to promulgate regional NO X 

### RACT controls and a NO X 

### cap-and-trade program. The adopted regional RACT deadline was 1995. By 1999, the NO X 

### Budget Program was implemented over the 12-state region from Maine to Washington, DC. In 2002, the USEPA reported that the NO X 

### Budget sources “emitted at a level approximately 12 percent below 2001 allocations” (USEPA, 2002). Progress continues with a more stringent cap taking effect in 2003.

• In 1997, eight OTR states petitioned th e USEPA under section 126 of the Clean Air Act, requesting NO X 

### emissions reductions on certain stationary sources in the Eastern U.S. In 1999, four more OTR members filed section 126 petitions. The USEPA granted four of the initial eight state petitions in 2000. g



### • In 2001, the states of the Ozone Trans port Commission agreed to support a suite

of model rules for inclusion in SIPs as appropriate to address 1-hour ozone problems. The model rules included controls for: (1) architectural and industrial maintenance coatings; (2) portable fuel containers; (3) cons umer products; (4) solvent cleaning; (5) mobile equipment re pair and refinishing; and (5) additional

g The initial eight section 126 OTR states were Conn ecticut, Maine, Massachusetts, New Hampshire, New York, Pennsylvania, Rhode Island, and Vermont. The additional four OTR members filing section 126 petitions were Delaware, the District of Columbia, Maryland, and New Jersey. The four granted petitions were from Connecticut, Massachusetts, New York, and Pennsylvania.The Nature of the Ozone Air Quality Problem in the Northeast: A Conceptual Description Page 4-11



### NO X 

### controls for industrial boilers, cement k ilns, stationary reciprocating engines, and stationary combustion engines.

These regional efforts have led the way for similar broader regional and national programs. For mobile sources, the USEPA promulgated its federal Reformulated Gasoline Program in 1995 and the National LEV program in 1998. For stationary sources, the USEPA announced in 1 997 that it would expand the OTR NO X 

### Budget Program through the NO X 

### SIP Call, which included 22 states and NO X 

### caps in place by

2003. The NO X 

### SIP Call also served as a response to the states’ Section 126 petitions

under the Clean Air Act.

In 2005, the USEPA took a further step to address the regional ozone problem by issuing the Clean Air Interstate Rule (CAIR), which requires additional NO X 

### reductions in 25 eastern states and the District of Columbia. The USEPA projects that CAIR will

achieve NO X 

### reductions of 2 million tons in 2015, a 61% decrease from 2003 levels. This will be a significant step forward in improvi ng air quality, but the time allowed to achieve

these reductions is later than the deadline many eastern states are facing to meet the current 8-hour ozone NAAQS. This, therefore, only partially provides the OTR with a regional measure that helps achieve the Clean Air Act’s goal of attaining the ozone air quality health standard within the Act’s mandatory deadlines.



## 4.5. Summary: Building upon success

A conceptual understanding of ozone as a regional problem in the OTR and throughout the eastern U.S. is now well establis hed. With this evolution in understanding, regional approaches to the ozone proble m are now underway, starting with the 1990 Clean Air Act Amendments that created the Ozone Transport Region. This initial regional approach, however, did not include large source regions outside of the OTR containing many large coal-fired power plants and other pollution sources contributing to the long-range transport of ozone into the OTR.

In 1998, the USEPA took another step in addressing the regional problem by finalizing the NO X 

### SIP Call, which covered emissions of NO X 

### , the main precursor of regional ozone, in additional parts of the Ea st. Even with these reductions, air quality modeling has projected conti nuing significant contributions from upwind sources in outof-state regions. As a result, the USEPA promulgated a further round of regional NO X 

### reductions in the East with the adoption of CAIR in 2005. With the modeling foundation for CAIR, the USEPA has presented a comp elling technical case on the need for additional regional NO X 

### reductions in the eastern U.S. to reduce ozone levels and protect public health. While states in the Northeast disagree with the extent of NO X 

### reductions and the timeline for those reductions to occur, the program is an excellent next step toward reducing ozone in the OTR.

There is a tendency to ch aracterize the nonattainment problems persisting after implementation of the USEPA’s Clean Air Inte rstate Rule and other federal programs as “residual,” but care must be taken in asse ssing these continuing nonattainment problems. A “residual” ozone problem is better characterized as a pe rsistent nonattainment problem that still requires broad regiona l responses coupled with local controls. As this conceptual description points out, one of the great lessons and successes seen in the history of airThe Nature of the Ozone Air Quality Problem in the Northeast: A Conceptual Description Page 4-12



### quality policy was the shift from urban-only air pollution control strategies to broader regional approaches in the East at the end of the 1990s (e.g., NO X 

### SIP Call). The danger exists, however, that the perception of a “res idual” ozone problem as being only a local issue will ignore the lessons learned from effective regional approaches.

The current suite of local and regional controls have a proven track record of success, and have helped to significantly lower NO X 

### , VOC, and ozone levels across the eastern U.S. As described earlier in this report, monitored NO X 

### emissions and ambient concentrations have dropped between 1997 and 2005, and the frequency and magnitude

of ozone exceedances have declined within th e OTR. To maintain the current momentum for improving air quality so that the OTR states can meet their attainment deadlines, there continues to be a need for more regional NO X 

### reductions coupled with appropriate local

NO X 

### controls and regional and local VOC controls.The Nature of the Ozone Air Quality Problem in the Northeast: A Conceptual Description Page 4-13



## References

Hudson, R. “A Conceptual Model for Ozone Transport.” University of Maryland, Dept. of Atmospheric and Oceanic Science. Prep ared for the Ozone Transport Commission. Draft Nov. 29, 2005.

NESCAUM. The Long Range Transport of Ozone and Its Precursors in the Eastern

United States . NESCAUM, Boston, MA, p.6, 1997.

Ryan, W.F. Air Quality Forecast Report Ph iladelphia Forecast Area 2002 . The Pennsylvania State University, Department of Meteorology, University Park, PA, March 2003 (available on-line at http://www.meteo.psu.edu/~wfryan/phl_2002_final_report.htm ).

USEPA. OTC NO X 

### Budget Program Compliance Report 2001 . U.S. Environmental Protection Agency, Washington, DC, p. 1, 2002.The Nature of the Ozone Air Quality Problem in the Northeast: A Conceptual Description Page A-1



# Appendix A: USEPA Guidance on Ozone Conceptual Description

From “Guidance on the Use of Models and Other Analyses in Attainment Demonstrations for the 8-hour Ozone NAAQS,” U.S. Environmental Protection Agency, EPA-454/R-05-002, Section 8, October 2005.

Note: At the time of this writing, the USEP A was incorporating Section 8 of the 8-hour ozone guidance into a new USEPA guidance document covering ozone, PM 2.5 

### , and regional haze. The new draft guidance is in Section 11 of Draft 3.2 “Guidance on the Use of Models and other Analyses for Demonstrating Attainment of Air Quality Goals for Ozone, PM 2.5 

### , and Regional Haze,” U.S. EPA, (Dra ft 3.2 – September 2006), available at http://www.epa.gov/ttn/scram/guidance_sip.htm#pm2.5 (accessed Oct. 5, 2006). The newer guidance, when finalized, may differ in some respects from the text given in Section 8 of the earlier ozone guidance.

Excerpt of Section 8 from EPA 8-hour ozone NAAQS guidance document:

8.0 How Do I Get Started? – A “Conceptual Description” 8.1 What Is A “Conceptual Description”? 8.2 What Types Of Analyses Might Be Useful For Developing And Refining A Conceptual Description? 8.2.1. Is regional transport an important factor affecting the

nonattainment area? 8.2.2. What types of meteorologi cal episodes lead to high ozone? 8.2.3. Is ozone limited by availability of VOC, NO X 

### or combinations of the two? Which source categories may be most important?The Nature of the Ozone Air Quality Problem in the Northeast: A Conceptual Description Page A-2



# Appendix A: USEPA Guidance on Ozone Conceptual Description

8.0 How Do I Get Started? - A “Conceptual Description”
A State/Tribe should start developing in formation to support a modeled attainment demonstration by assembling and reviewing available air quality, emissions and meteorological data. Baseline design values should be calculated at each ozone monitoring site, as described in Section 3. If past modeling has been performed, the emission scenarios examined and air quality predictions may also be useful. Readily available information should be used by a Stat e/Tribe to develop an initial conceptual description of the nonattainment problem in the area which is the focus of a modeled attainment demonstration. A conceptual de scription is instrumental for identifying potential stakeholders and for developing a modeling/analysis protocol. It may also influence a State’s choice of air quality model, modeling domain, grid cell size, priorities for quality assuring and refining emissions estim ates, and the choice of initial diagnostic tests to identify potentially effective cont rol strategies. In general, a conceptual description is useful for helping a State/Trib e identify priorities and allocate resources in performing a modeled attainment demonstration.

In this Section, we identify key parts of a conceptual description. We then present examples of analyses which could be used to describe each of these parts. We note that initial analyses may be complemented later by additional efforts performed by those implementing the protocol.

8.1 What Is A “Conceptual Description”?

A “conceptual description” is a qualitative way of characterizing the nature of an area’s nonattainment problem. It is best described by identifying key components of a description. Examples are listed below. The examples are not necessarily comprehensive.

There could be other features of an area’s problem which are important in particular cases. For purposes of illustration later in th e discussion, we have answered each of the questions posed below. Our res ponses appear in parentheses.

1. Is the nonattainment problem primaril y a local one, or are regional factors important?

(Surface measurements suggest transport of ozone close to 84 ppb is likely. There are some other nonattainment areas not too far distant.)

2. Are ozone and/or precursor co ncentrations aloft also high?

(There are no such measurements.)The Nature of the Ozone Air Quality Problem in the Northeast: A Conceptual Description Page A-3



### 3. Do violations of the NAAQS occur at several monitoring sites throughout the nonattainment area, or are they confined to one or a small number of sites in proximity to one another?

(Violations occur at a limited number of sites, located throughout the area.)

4. Do observed 8-hour daily maximum ozone concentrations exceed 84 ppb frequently or just on a few occasions?

(This varies among the monitors from 4 times up to 12 times per year.)

5. When 8-hour daily maxima in excess of 84 ppb occur, is there an accompanying characteristic spatial pattern, or is th ere a variety of spatial patterns?

(A variety of patterns is seen.)

6. Do monitored violations occur at locations subject to mesoscale wind patterns (e.g., at a coastline) which may di ffer from the general wind flow?

(No.)

7. Have there been any recent major changes in emissions of VOC or NO X 

### in or

near the nonattainment area? If so, what changes have occurred?

(Yes, several local measures [include a list] believed to result in major reductions in VOC [quantify in tons per summer day] have been implemented in the last five years. Additionally, the area is expe cted to benefit from the regional NO X 

### reductions from the NO X 

### SIP call.)

8. Are there discernible trends in desi gn values or other air quality indicators which have accompanied a change in emissions?

(Yes, design values have decreased by a bout 10% at four sites over the past [x] years. Smaller or no reductions are seen at three other sites.)

9. Is there any apparent spatial patte rn to the trends in design values?

(No.)

10. Have ambient precursor concentrations or measured VOC species profiles changed?

(There are no measurements.)The Nature of the Ozone Air Quality Problem in the Northeast: A Conceptual Description Page A-4



### 11. What past modeling has been performed and what do the results suggest?

(A regional modeling analysis has been performed. Two emission scenarios were

modeled: current emissions and a substantial reduction in NO X 

### emissions throughout the regional domain. Reduced NO X 

### emissions led to substantial predicted reductions in 8-hour daily ma ximum ozone in most locations, but changes near the most populated area in the nonattainment area in question were small or nonexistent.)

12. Are there any distinctive meteorologica l measurements at the surface or aloft which appear to coincide with occasions with 8-hour daily maxima greater than 84 ppb?

(Other than routine soundi ngs taken twice per day, there are no measurements

aloft. There is no obviou s correspondence with meteorological measurements other than daily maximum temperatures are always > 85 F on these days.)

Using responses to the preceding questions in this example, it is possible to construct an initial conceptu al description of the nonattainment area’s ozone problem. First, responses to questions 1 and 11 suggest there is a significant regional component to the area’s nonattainment problem. Second, res ponses to questions 3, 4, 7, 8, and 11 indicate there is an import ant local component to the ar ea’s nonattainment problem. The responses to questions 4, 5 and 12 indicat e that high ozone concentrations may be

observed under several sets of meteorological conditions. The responses to questions 7, 8, and 11 suggest that ozone in and near the nonattainment area may be responsive to both

VOC and NO X 

### controls and that the extent of this response may vary spatially. The response to question 6 suggests that it may be appropriate to develop a strategy using a model with 12 km grid cells.

The preceding conceptual description imp lies that the State/Tribe containing the nonattainment area in this example will need to involve stakeholders from other, nearby States/Tribes to develop and implement a m odeling/analysis protoc ol. It also suggests that a nested regional modeling analysis will be needed to address the problem. Further, it may be necessary to model at least several distinctive types of episodes and additional analyses will be needed to select episodes. Finally, sensitivity (i.e., diagnostic) tests, or other modeling probing tools, will be needed to assess the effects of reducing VOC and

NO X 

### emissions separately and at the same time.

It should be clear from the preceding example that the initial conceptual description of an area’s nonattainment problem may draw on readily available

information and need not be detailed. It is intended to help launch development and implementation of a modeling/analysis protocol in a productive direction. It will likely be supplemented by subsequent, more extensive modeling and ambient analyses performed by or for those implementing the modeling/analysis protocol discussed in Section 9.The Nature of the Ozone Air Quality Problem in the Northeast: A Conceptual Description Page A-5



### 8.2 What Types Of Analyses Migh t Be Useful For Developing And Refining A Conceptual Description?

Questions like those posed in Section 8. 1 can be addressed using a variety of analyses ranging in complexity from an insp ection of air quality da ta to sophisticated mathematical analyses. We anticipate the simpler analyses will often be used to develop the initial conceptual description. These will be followed by more complex approaches or by approaches requiring more extensive data ba ses as the need later becomes apparent. In the following paragraphs, we revisit key parts of the conceptual description identified in Section 8.1. We note analyses which may help to develop a description of each part. The

list serves as an illustration. It is not necessarily exhaustive.

8.2.1. Is regional transport an import ant factor affecting the nonattainment

area?

- Are there other nonattainment areas within a day’s transport of the nonattainment area?

- Do “upwind” 8-hour daily maximum ozone concentrations approach or exceed 84 ppb on some or all of the days with observed 8-hour daily maxima > 84 ppb in the

nonattainment area? - Are there major sources of emissions upwind? - What is the size of the downwind/upwind gradient in 8-hour daily maximum ozone concentrations compared to the upwind values?

- Do ozone concentrations aloft but within the planetary boundary layer approach or exceed 84 ppb at night or in the morning hour s prior to breakup of the nocturnal surface

inversion? - Is there a significant positive correla tion between observed 8-hour daily maximum ozone concentrations at most monitoring si tes within or near the nonattainment area? - Is the timing of high observed ozone consistent with impacts estimated from upwind areas using trajectory models? - Do available regional modeling simulations suggest that 8-hour daily maximum ozone

concentrations within the nonattainment area respond to regional control measures? - Does source apportionment modeling indica te significant contribu tions to local ozone from upwind emissions?

8.2.2. What types of meteorological episodes lead to high ozone?

- Examine the spatial patterns of 8-hour dail y maxima occurring on days where the ozone is > 84 ppb and try to identify a limi ted number of distinctive patterns. - Review synoptic weather charts for days having observed concentrations > 84 ppb to identify classes of synoptic scale feat ures corresponding to high observed ozone.

- Perform statistical analyses between 8-hour daily ma ximum ozone and meteorological

measurements at the surface and aloft to identify distinctive classes of days corresponding with observed daily maxima > 84 ppb.The Nature of the Ozone Air Quality Problem in the Northeast: A Conceptual Description Page A-6



### 8.2.3. Is ozone limited by availability of VOC, NO X 

### or combinations of the two? Which source categories may be most important?

- What are the major source categories of VOC and NO X 

### and what is their relative importance in the most recent inventory? - Review results from past modeling analyses to assess the likeli hood that ozone in the nonattainment area will be more responsive to VOC or NO X 

### controls. Do conclusions vary for different locations? - Apply modeling probing tools (e.g., source apportionment modeling) to determine which source sectors appear to contri bute most to local ozone formation. - Apply indicator species methods such as those described by Sillman (1998, 2002) and Blanchard (1999, 2000, 2001) at sites with a ppropriate measurements on days with 8- hour daily maximum ozone exceedances. Identify classes of days where further ozone formation appears limited by available NO X 

### versus classes of days where further ozone formation appears limited by available VOC. Do the conclusions differ for different days? Do the results differ on weekdays versus weekends? - Apply receptor modeling approaches such as those described by Watson (1997, 2001), Henry (1994) and Henry (1997a, 1997b, 1997c) to identify source categories contributing to ambient VOC on days with high observed ozone. Do the conclusions differ on days when measured ozone is not high?

Additional analyses may be identified as issues arise in implementing a modeling/analysis protocol. These analyses ar e intended to channel resources available to support modeled attainment demonstrations onto the most productive paths possible. They will also provide other pieces of information which can be used to reinforce conclusions reached with an air quality mode l, or cause a reassessment of assumptions made previously in applying the model. As noted in Section 4, corroboratory analyses should be used to help assess whether a simu lated control strategy is sufficient to meet the NAAQS.The Nature of the Ozone Air Quality Problem in the Northeast: A Conceptual Description Page A-7



## References

Blanchard, C.L., F.W. Lurmann, P.M. Roth , H.E. Jeffries and M. Korc. “The use of ambient data to corroborate analys es of ozone control strategies.” Atmos. Envt. 33 , 369- 381, 1999.

Blanchard, C. L. “Ozone proce ss insights from field experiments

– Part III: Extent of

reaction and ozone formation.” Atmos. Envt. 34 , 2035-2043, 2000.

Blanchard, C. L., and T. Stoeckenius. “Oz one response to precursor controls: comparison of data analysis methods with the predic tions of photochemical air quality simulation

models.” Atmos. Envt. 35 , 1203-1216, 2001.

Henry, R.C., C.W. Lewis, and J.F. Co llins. “Vehicle-related hydrocarbon source compositions from ambient data: The GRACE/SAFER Method.” Envtl. Sci. & Technol.

28 , 823-832, 1994.

Henry, R.C. “Receptor Model Applied to Patterns in Space (RMA PS) Part I. Model description.” J. Air & Waste Mgmt. Assoc. 47 , 216-219, 1997a.

Henry, R.C. “Receptor Model Applied to Patterns in Space (RMAPS) Part II. Apportionment of airborne particulat e sulfur from Project MOHAVE.” J. Air & Waste Mgmt. Assoc. 47 , 220-225, 1997b.

Henry, R.C. “Receptor Modeling Applied to Patterns in Space (RMAPS) Part III. Apportionment of airborne particulate sulfur in western Washington State.” J. Air & Waste Mgmt. Assoc. 47 , 226-230, 1997c.

Sillman, S. “Evaluating the Relation between Ozone, NO X 

### and Hydrocarbons: The Method of Photochemical Indicators.” EPA/600R-98/022, http://wwwpersonal.engin.umich.edu/~sillman/publications.htm , 1998.

Sillman, S., and D. He. “Some th eoretical results concerning O 3 

### -NO X 

### -VOC chemistry

and NO X 

### -VOC indicators.” J. Geophys. Res. 107 , 4659-4673, 2002.

Watson, J.G. “Observational Models: The Use of Chemical Mass Balance Methods.” Prepared for the U.S. EPA Source Attribution Workshop, Research Triangle Park, NC, July 16-18, 1997, available at http://www.epa. gov/ttn/faca/stissu.html, Source Attribution Workshop Materials, 1997.

Watson, J.G., J.C. Chow, and E.M. Fujita. “Review of volatile organic compound source apportionment by chemical mass balance.” Atmos. Envt. 35 , 1567-1584, 2001.The Nature of the Ozone Air Quality Problem in the Northeast: A Conceptual Description Page B-1



# Appendix B: Ozone pattern classifications

in the OTRThe Nature of the Ozone Air Quality Problem in the Northeast: A Conceptual Description Page B-2



# Appendix B: Ozone pattern classifications in the OTR

The following five types of ozone patterns in the OTR are taken from: Stoeckenius, T. and Kemball-Cook, S. “Determination of re presentativeness of 2002 ozone season for ozone transport region SIP modeling.” Final Report prepared for the Ozone Transport Commission, 2005. Figure B-1 shows the 850 mb height and wind fi elds and Figure B-2 shows the surface temperatures and 10 meter wind fields for the five patterns (reproduced from Figures 3-2 and 3-5 of Stoeckenius & Kemball-Cook, 2005).

“Type A”

– High ozone throughout the OTR. This pattern is characterized by strong high pressure over the southeastern states exte nding from the surface to 500 mb with high temperatures extending into New England and southwest surface winds throughout the OTR. The 850 mb temperatures and heights, and surface temperatures are above average at all locations except Washington DC; winds are southwest to west throughout the OTR except more variable at LaGuardia and magn itudes of resultant wind vectors are higher than average (indicative of a fairly steady, well defined flow regime), east-west surface pressure gradients are near neutral but southwest-northeast grad ients along the I-95 corridor and in the west (Pittsburgh to Buffalo) are positive, which is consistent with the

southwest flow. The stable air mass and hi gh temperatures promote ozone formation throughout the OTR under these conditions.

“Type B”

– High ozone confined to th e extreme southeastern OTR. This pattern is characterized by an upper-level trough offshor e of the OTR and a surface high centered over Kentucky. This results in cooler air advection over nearly all of the OTR with northwest flow aloft and a more westerly flow at the surface. The 850 mb heights are lower than average (especially in New Engl and) and surface winds are more frequently from the northwest along the I-95 corridor th an under Type A. Temperatures at 850 mb along the I-95 corridor are onl y slightly cooler than under Type A but inland temperatures, especially in the north, are much cooler (e.g., at Buffalo); similarly, surface temperatures along the I-95 corridor ar e about the same as under Type A but temperatures are cooler in Buffalo and Alba ny. Type B events have the strongest positive west-east surface pressure gradients of any cat egory, consistent with the northwest winds but gradients from Washington to New York a nd Boston are positive. The cooler air over the western OTR and westerly to northweste rly flow result in th e higher ozone levels being confined to just the extreme southe rn portion of the OTR under this pattern.

“Type C”

– High ozone along the I-95 corridor and northern New England. This pattern is characterized by an extension of the semi-permanent Bermuda high into the southeastern U.S. and an area of high surface and 850 mb temperatures extending from Maryland to Maine; the 500 mb pa ttern is nearly zonal (east-we st flow) while flow at the surface is generally from the southwest. Th e 850 mb heights are intermediate between Type A and Type B but 850 mb temperatures are very high along the I-95 corridor and slightly cooler further inland. Winds are more consistently south - southwest at all sites than under other episode types and almost no northwest-north-northeas t winds are seen at LaGuardia in contrast to other types. Resu ltant wind vector magnitudes are much higherThe Nature of the Ozone Air Quality Problem in the Northeast: A Conceptual Description Page B-3



### than average, consistent with the steady s outhwest flow. Southwest – northeast pressure gradients along the I-95 corridor and from Pittsburgh to Buffalo are positive, consistent with the southwest flow. Average east-west pressure gradients are near zero. These

conditions result in above aver age ozone levels al l along the I-95 corridor with advection north into coastal and interior New England. Ozone levels are slightly below average in

the extreme southeastern and western OTR.

“Type D”

– High ozone in the western OTR . This pattern is characterized by an area of mean upper level divergence with associated cut-off low at 850 mb off the Outer Banks of North Carolina. A relatively vigorous mean low pressure center can be seen at the surface. An east-west temperature gradient across the OTR is evident at 850 mb. Surface temperatures along the I-95 corridor and in Albany are below average but surface temperature is above average at Buffalo. The 850 mb heights ar e the highest of any episode type due to a strong ridge over Ne w England. Surface winds are mostly eastnortheast along the I-95 corridor from DC to Ne w York but more variable further north. In contrast to episode types A, B, or C, the southwest-northeast pressure gradients along the I-95 corridor are negative, consistent with the northeast surface winds. West-east pressure gradients are flat. These conditions result in below average ozone in the eastern

OTR due to the on-shore flow in the north a nd cyclonic conditions in the south but above average ozone levels in the western OTR due to stable, warm conditions with light winds.

“Type E”

– Generally low ozone throughout the OTR . This category includes days with moderately low to lowest average ozone read ings of all OTR exceedance days used in the characterization scheme. The Bermuda high is shifted east relative to the other types and flow over the southeastern U.S. is only weak ly anti-cyclonic with a nearly zonal flow pattern at the 850 and 500 mb levels over the OTR. Temperatures at the surface and aloft are the coolest of any episode type. While wi nds aloft are nearly westerly, surface winds are generally south-southeast over most of the OTR. The southwest-northeast pressure gradients are negative along the I-95 corrido r and east-west gradients are positive,

consistent with the southeast flow. These conditions result in below average ozone throughout the OTR due to the relatively lo w temperatures and s outheasterly onshore

flow at coastal locations.The Nature of the Ozone Air Quality Problem in the Northeast: A Conceptual Description Page B-4

Figure B-1. Average 850 mb height and wind fiel ds for each episode (pattern) type identified by Stoeckenius and Kemball-Cook (pattern numbers refer to the episode types listed in text): Pattern 1 = Episode Type E, 2 = B, 3 = A, 4 = D, 5 = C) (Figure 3-2 of Stoeckenius & Kemball-Cook (2005)).The Nature of the Ozone Air Quality Problem in the Northeast: A Conceptual Description Page B-5

Figure B-2. Average surface temperat ure and 10 m wind fields for each episode (pattern) type identified by Stoeckenius and Kemball-Cook (pattern numbers refer to the episode types listed in text): Pattern 1 = Episode Type E, 2 = B, 3 = A, 4 = D, 5 = C) (Figure 3-5 of Stoeckenius & Kemball-Cook (2005)).The Nature of the Ozone Air Quality Problem in the Northeast: A Conceptual Description Page C-1



# Appendix C: Exceedance days by monitor

in the OTRThe Nature of the Ozone Air Quality Problem in the Northeast: A Conceptual DescriptionPage C-2Appendix C: Exceedance daysby monitor in the OTRTables of the number of 8-hour ozone NAAQSexceedance days recorded at individual monitors in the OTR nonattainment/attainmentareas for the 1997-2005 ozone seasons. Hourly data were downloaded in January 2006 from the USEPA Air Quality System (AQS)database. The number of 8-hour ozone exceedance days were calculated using procedures specified in USEPA’s “Guideline on DataHandling Conventions for the 8-hour OzoneNAAQS” (OAQPS, EPA-454/R-98-017, Dec. 1998) withflagged data (due to a regionalforest fire smoke event) eliminated from the analysis. While these tables are derived from the publicly available data in the USEPAAQS database, states may have monitoring datathat differ from these. For example,the tables contain state-specific data provided bythe Maryland Department of the Environment and the New JerseyDepartment of EnvironmentalProtection that differ from theUSEPA AQS database at the time the datawere downloaded in January2006. “***” indicates years during which a monitor was notin operation or had less than 75 percentdata collection during the ozone season.Philadelphia-Wilmington-Atlantic City, PA-NJ-MD-DE (Classification: MODERATE)AQS MONITOR ID COUNTY MONITOR NAME ST8-hr Ozone exceedance days1997 1998 1999 2000 2001 2002 2003 2004 2005100010002 Kent Killens Pond DE 14 17 13 5 8 10 3 0 2100031003 New Castle Bellefonte DE 6 8 10 5 5 11 *** *** ***100031007 New Castle Lums Pond DE 15 12 12 5 9 9 4 0 6100031010 New Castle Brandywine Creek DE 17 17 16 7 15 18 3 3 3100031013 New Castle Wilmington (Bellefonte2) DE *** *** *** *** *** 8 3 1 4100051002 Sussex Seaford DE 14 16 17 5 4 10 4 0 3100051003 Sussex Lewes DE *** 17 17 6 10 14 4 2 7240150003 Cecil Fairhill MD 19 20 20 18 16 17 6 3 9340010005 Atlantic Nacote Creek NJ 18 24 14 4 9 11 4 0 3340070003 Camden Camden Lab NJ 12 15 16 6 19 19 4 3 5340071001 Camden Ancora NJ 23 29 25 10 17 27 9 6 12340110007 Cumberland Millville NJ 14 17 17 6 14 20 6 2 4340150002 Gloucester ClarksboroNJ 19 22 21 8 17 24 6 4 6340210005 Mercer Rider Univ. NJ 16 17 24 11 15 26 7 1 7340290006 Ocean Colliers Mills NJ 21 28 23 11 21 30 9 8 14420170012 Bucks Bristol PA 14 17 24 14 16 17 9 2 7The Nature of the Ozone Air Quality Problem in the Northeast: A Conceptual DescriptionPage C-3Philadelphia-Wilmington-Atlantic City, PA-NJ-MD-DE (Classification: MODERATE)AQS MONITOR ID COUNTY MONITOR NAME ST8-hr Ozone exceedance days1997 1998 1999 2000 2001 2002 2003 2004 2005420290050 Chester West Chester PA *** *** *** *** 20 19 4 *** ***420290100 Chester New Garden PA *** *** *** *** 17 23 4 5 8420450002 Delaware Chester PA 19 17 19 7 12 16 3 2 4420910013 Montgomery Norristown PA 19 17 20 11 18 12 4 1 8421010004 Philadelphia Philadelphia - Downtown PA 0 1 2 1 0 0 2 0 0421010014 Philadelphia Philadelphia - Roxborough PA 10 7 *** 4 10 13 2 0 3421010024 Philadelphia Philadelphia - NEAirport PA 17 15 *** 5 13 22 4 6 8421010136 Philadelphia Philadelphia - Elmwood PA 0 4 12 3 5 13 2 0 ***Baltimore, MD (Classification: MODERATE)AQS MONITOR ID COUNTY MONITOR NAME ST8-hr Ozone exceedance days1997 1998 1999 2000 2001 2002 2003 2004 2005240030014 Anne Arundel Davidsonville MD 20 42 31 7 14 25 5 4 9240030019 Anne Arundel Fort Meade MD 24 25 27 10 19 20 3 5 ***240051007 Baltimore Padonia MD 10 7 14 3 9 19 2 1 2240053001 Baltimore Essex MD 10 11 11 3 10 14 3 2 6240130001 Carroll South Carroll MD 9 18 16 5 10 10 2 1 5240251001 Harford Edgewood MD 18 17 17 11 20 25 7 6 11240259001 Harford Aldino MD 20 12 17 8 18 22 4 3 10245100053 Baltimore (City) Baltimore-Ponca St MD *** *** *** *** *** 8 *** *** ***245100050 Baltimore (City) Baltimore-0050 MD 16 *** *** *** *** *** *** *** ***245100051 Baltimore (City) Baltimore-0051 MD 9 5 7 *** *** *** *** *** ***New York-N. New Jersey-Long Island, NY-NJ-CT (Classification: MODERATE)AQS MONITOR ID COUNTY MONITOR NAME ST8-hr Ozone exceedance days1997 1998 1999 2000 2001 2002 2003 2004 200590010017 Fairfield Greenwich CT 13 8 14 3 13 18 7 1 890011123 Fairfield Danbury CT 14 9 17 7 9 17 4 4 11The Nature of the Ozone Air Quality Problem in the Northeast: A Conceptual DescriptionPage C-4New York-N. New Jersey-Long Island, NY-NJ-CT (Classification: MODERATE)AQS MONITOR ID COUNTY MONITOR NAME ST8-hr Ozone exceedance days1997 1998 1999 2000 2001 2002 2003 2004 200590013007 Fairfield Stratford CT 17 11 9 4 10 20 8 2 890019003 Fairfield Westport CT 15 13 13 3 15 19 6 2 1090010113 Fairfield Bridgeport CT 6 *** *** *** *** *** *** *** ***90070007 Middlesex Middletown CT 12 5 15 6 11 16 7 1 790091123 &90090027New Haven New Haven CT 7 3 5 *** *** *** *** 1 290093002 New Haven Madison CT 19 9 16 6 11 19 9 2 890099005 New Haven Hamden CT *** *** 11 2 9 14 7 *** ***340030005 Bergen Teaneck NJ *** *** *** 2 10 18 4 2 8340030001 Bergen Cliffside Park NJ 5 *** *** *** *** *** *** *** ***340130011 &340130016Essex Newark Lab NJ 6 5 6 *** *** 6 *** *** ***340170006 Hudson Bayonne NJ 9 7 17 3 6 6 2 1 6340190001 Hunterdon Flemington NJ 18 21 23 9 12 19 7 6 13340230011 Middlesex Rutgers Univ. NJ 16 15 23 10 17 26 5 2 10340250005 Monmouth Monmouth Univ. NJ 12 20 12 5 8 17 10 2 8340273001 Morris Chester NJ 13 22 21 6 15 27 5 0 3340315001 Passaic Ramapo NJ *** 8 16 1 9 13 2 2 8340390008 Union Plainfield NJ 5 *** *** *** *** *** *** *** ***360050080 Bronx NYC-Morrisania Center NY 5 1 5 *** *** *** *** *** ***360050083 BronxNYC-200thSt & SouthernBlvdNY 5 0 8 1 1 6 2 1 0360050110 Bronx NYC-IS52 NY *** *** *** 1 *** 6 2 0 1360610010 New York NYC-Mabel Dean HS NY *** 2 3 0 *** *** *** *** ***360610063 New York NYC-Roof WTC NY 16 22 18 5 12 *** *** *** ***360810004 Queens NYC-Queens College NY 10 *** *** *** *** *** *** *** ***360810097 Queens NYC-QBORO NY *** *** 10 3 3 *** *** *** ***360810098 Queens NYC-College Pt NY *** *** *** 1 1 1 1 0 0360810124 Queens NYC-Queens NY *** *** *** *** *** 7 4 0 4360850067 Richmond NYC-Susan Wagner HS NY 21 12 17 11 10 19 5 2 8The Nature of the Ozone Air Quality Problem in the Northeast: A Conceptual DescriptionPage C-5New York-N. New Jersey-Long Island, NY-NJ-CT (Classification: MODERATE)AQS MONITOR ID COUNTY MONITOR NAME ST8-hr Ozone exceedance days1997 1998 1999 2000 2001 2002 2003 2004 2005361030002 Suffolk Babylon NY 8 10 11 4 2 9 6 2 6361030004 Suffolk Riverhead NY 11 9 16 4 3 6 3 *** 6361030009 Suffolk Holtsville NY *** *** *** 4 8 18 6 2 ***361192004 Westchester White Plains NY 11 6 12 2 8 15 4 0 9Washington, DC-MD-VA (Classification: MODERATE)AQS MONITOR ID COUNTY MONITOR NAME ST8-hr Ozone exceedance days1997 1998 1999 2000 2001 2002 2003 2004 2005110010025 District of Columbia (all) Takoma DC 11 18 15 5 7 13 3 2 1110010041 District of Columbia (all) River Terrace DC 12 11 16 2 7 12 2 0 1110010043 District of Columbia (all) McMillian Reservoir DC 18 20 22 2 12 21 3 3 5240090010 &240090011Calvert Calvert MD 4 10 10 5 5 *** *** *** 2240170010 Charles S. Maryland MD 17 30 31 5 9 15 6 1 6240210037 Frederick Frederick Municipal Airport MD *** *** 19 4 14 13 3 1 1240313001 Montgomery Rockville MD 13 22 16 2 11 11 3 2 3240330002 Prince George's Greenbelt MD 24 24 23 7 19 15 3 *** ***240338001 Prince George's Suitland MD 14 25 18 3 14 *** *** *** ***240338003 Prince George's Equestrian Center MD *** *** *** *** *** 15 4 5 5510130020 Arlington Co Aurora Hills VA 17 10 21 3 12 18 4 4 5510590005 Fairfax Chantilly (Cub Run) VA 2 16 6 2 9 12 2 3 0510590018 Fairfax Mount Vernon VA *** 17 16 4 10 16 5 6 8510590030 Fairfax Franconia VA *** *** 19 0 14 18 5 5 6510591004 &510591005FairfaxSeven Corners &AnnandaleVA 10 17 9 2 *** 20 3 4 4510595001 Fairfax McLean – Lewinsville VA 3 7 6 2 8 7 3 3 2511071005 Loudoun Ashburn VA *** 17 7 1 9 23 3 2 ***511530009 Prince William James S. Long Park VA 4 13 9 2 6 7 4 1 0515100009 Alexandria (City) Alexandria VA 5 10 10 2 6 10 3 3 2The Nature of the Ozone Air Quality Problem in the Northeast: A Conceptual DescriptionPage C-6Jefferson Co., NY (Classification: MODERATE)AQS MONITOR ID COUNTY MONITOR NAME ST8-hr Ozone exceedance days1997 1998 1999 2000 2001 2002 2003 2004 2005360450002 Jefferson Perch River NY 8 4 6 1 17 13 9 2 3Greater Connecticut, CT (Classification: MODERATE)AQS MONITOR ID COUNTY MONITOR NAME ST8-hr Ozone exceedance days1997 1998 1999 2000 2001 2002 2003 2004 200590031003 Hartford East Hartford CT 7 2 11 2 8 10 0 1 590050005 Litchfield Cornwall (Mohawk Mt) CT *** *** *** *** *** 13 4 2 890050006 Litchfield Torrington CT 9 10 12 4 *** *** *** *** ***90110008 New London Groton CT 17 3 11 3 7 7 5 1 490131001 Tolland Stafford CT 10 8 12 1 10 13 1 2 8Boston-Lawrence-Worcester (E. MA),MA (Classification: MODERATE)AQS MONITOR ID COUNTY MONITOR NAME ST8-hr Ozone exceedance days1997 1998 1999 2000 2001 2002 2003 2004 2005250010002 Barnstable Truro MA 17 2 12 3 13 9 8 3 7250051002 Bristol Fairhaven MA 12 2 8 3 8 5 8 1 1250051005 Bristol Easton MA 7 7 3 0 14 *** *** *** ***250070001 DukesWampanoag Laboratory –Martha’s VineyardMA *** *** *** *** *** *** *** 0 4250095005 Essex Lawrence-Haverhill MA 2 1 1 0 0 6 *** *** 0250092006 Essex Lynn MA 6 7 6 1 11 13 3 2 6250094004 Essex Newbury MA 6 6 6 0 8 9 2 1 0250170009 MiddlesexUSEPA Region 1 Lab –ChelmsfordMA *** *** *** *** *** *** *** *** 2250171102 Middlesex Stow MA *** 5 8 1 12 8 0 1 2250171801 Middlesex Sudbury MA 6 4 *** *** *** *** *** *** ***250174003 Middlesex Waltham MA 6 7 5 *** *** *** *** *** ***250213003 Norfolk E Milton (Blue Hill) MA *** *** *** *** *** 17 5 2 4The Nature of the Ozone Air Quality Problem in the Northeast: A Conceptual DescriptionPage C-7Boston-Lawrence-Worcester (E. MA),MA (Classification: MODERATE)AQS MONITOR ID COUNTY MONITOR NAME ST8-hr Ozone exceedance days1997 1998 1999 2000 2001 2002 2003 2004 2005250250041 Suffolk Boston-Long Island MA *** *** 4 0 9 10 1 1 5250250042 Suffolk Boston-Roxbury MA *** *** 0 0 2 2 1 1 1250251003 Suffolk Chelsea MA 2 4 3 *** *** *** *** *** ***250270015 Worcester Worcester MA 5 6 8 1 6 *** 1 0 5Providence (All RI), RI (Classification: MODERATE)AQS MONITOR ID COUNTY MONITOR NAME ST8-hr Ozone exceedance days1997 1998 1999 2000 2001 2002 2003 2004 2005440030002 Kent W Greenwich RI 10 4 7 5 13 12 1 2 5440071010 Providence E Providence RI 3 2 2 2 10 9 4 2 4440090007 Washington Narragansett RI *** 1 11 4 11 8 8 4 5Springfield (Western MA), MA (Classification: MODERATE)AQS MONITOR ID COUNTY MONITOR NAME ST8-hr Ozone exceedance days1997 1998 1999 2000 2001 2002 2003 2004 2005250034002 Berkshire Adams MA *** *** 1 *** 16 4 2 1 6230130003 Hampden Agawam MA 9 1 1 1 2 6 *** *** ***250130008 Hampden Chicopee MA 7 5 7 1 9 10 3 1 8250150103 Hampshire South Hadley (Amherst) MA 2 2 3 1 3 4 0 1 1250154002 Hampshire Ware MA 9 6 9 2 12 10 0 3 8Poughkeepsie, NY (Classification: MODERATE)AQS MONITOR ID COUNTY MONITOR NAME ST8-hr Ozone exceedance days1997 1998 1999 2000 2001 2002 2003 2004 2005360270007 Dutchess Millbrook NY 7 8 8 2 8 8 0 1 3360715001 Orange Valley Central NY 6 6 8 1 12 4 4 2 7360790005 Putnam Mt Ninham NY 7 8 15 1 10 19 2 1 7The Nature of the Ozone Air Quality Problem in the Northeast: A Conceptual DescriptionPage C-8Boston-Manchester-Portsmouth (SE), NH (Classification: MODERATE)AQS MONITOR ID COUNTY MONITOR NAME ST8-hr Ozone exceedance days1997 1998 1999 2000 2001 2002 2003 2004 2005330110016 &330110019 &330110020Hillsborough Manchester NH 3 0 *** 0 *** 4 0 1 0330111010 &330111011Hillsborough Nashua NH 4 3 8 1 7 5 1 2 1330150009 &330150015 &330150014Rockingham Portsmouth NH 5 3 5 0 *** 8 0 1 0330150013 Rockingham Brentwood NH *** 0 1 0 4 10 *** *** ***330150012 &330150016Rockingham Rye NH 9 4 3 0 7 7 0 1 0330173002 Strafford Rochester NH 1 0 2 0 1 6 0 *** ***Kent and Queen Anne’s Cos., MD (Classification: MARGINAL)AQS MONITOR ID COUNTY MONITOR NAME ST8-hr Ozone exceedance days1997 1998 1999 2000 2001 2002 2003 2004 2005240290002 Kent Millington MD 19 16 22 6 13 17 4 1 3Lancaster, PA (Classification: MARGINAL)AQS MONITOR ID COUNTY MONITOR NAME ST8-hr Ozone exceedance days1997 1998 1999 2000 2001 2002 2003 2004 2005420710007 Lancaster Lancaster PA 21 27 18 5 15 18 3 1 6The Nature of the Ozone Air Quality Problem in the Northeast: A Conceptual DescriptionPage C-9Portland, ME (Classification: MARGINAL)AQS MONITOR ID COUNTY MONITOR NAME ST8-hr Ozone exceedance days1997 1998 1999 2000 2001 2002 2003 2004 2005230050027 Cumberland Portland ME *** *** *** *** *** *** *** 0 0230052003 Cumberland Cape Elizabeth ME 6 5 2 0 8 5 0 0 0230230003 &230230004SagadahocPhippsburg/Georgetown(Reid State Park)ME 7 4 4 1 *** 5 1 0 0230313002 York Kittery ME 7 4 4 0 4 12 2 1 0230312002 York Kennebunkport ME 5 5 5 1 8 10 2 1 0230310037 &230310038York Hollis ME 2 0 1 0 *** 3 0 0 0Buffalo-Niagara Falls, NY (Classification: SUBPART 1)AQS MONITOR ID COUNTY MONITOR NAME ST8-hr Ozone exceedance days1997 1998 1999 2000 2001 2002 2003 2004 2005360290002 Erie Amherst NY 0 13 6 4 10 21 7 0 5360631006 Niagara Middleport NY 1 6 7 3 10 16 6 0 4Youngstown-Warren-Sharon, OH-PA (Classification: SUBPART 1)AQS MONITOR ID COUNTY MONITOR NAME ST8-hr Ozone exceedance days1997 1998 1999 2000 2001 2002 2003 2004 2005390990009 &390990013Mahoning Youngstown - Oakhill OH 3 15 7 1 5 14 4 1 2391550008 &391550011Trumbull Warren-Trumbull County OH 8 19 10 2 12 24 5 2 5391550009 Trumbull Kinsman OH 7 15 10 2 5 16 4 0 2420850100 Mercer Farrell PA 9 24 8 2 15 20 6 1 4The Nature of the Ozone Air Quality Problem in the Northeast: A Conceptual Description Page C-10Pittsburgh-Beaver Valley, PA (Classification: SUBPART 1)AQS MONITOR ID COUNTY MONITOR NAME ST8-hr Ozone exceedance days1997 1998 1999 2000 2001 2002 2003 2004 2005420030008 Allegheny Lawrenceville PA 7 14 10 3 4 16 5 0 1420030010 Allegheny Pittsburg PA *** 6 16 4 9 25 5 0 4420030067 Allegheny South Fayette PA 8 24 15 4 7 17 4 1 4420030088 Allegheny Penn Hills PA 5 16 11 4 *** *** *** *** ***420031005 Allegheny Harrison Township PA 12 18 14 4 8 14 2 0 6420050001 Armstrong Kittanning PA *** 21 18 2 16 15 5 1 4420070002 Beaver Hookstown PA 4 11 9 1 9 19 6 0 5420070005 Beaver Brighton Township PA 3 15 11 1 8 23 3 0 4420070014 Beaver Beaver Falls PA 5 10 6 3 4 9 3 0 2421250005 Washington Charleroi PA 14 34 11 3 7 14 4 0 2421250200 Washington Washington PA 6 15 11 3 6 9 5 0 4421255001 Washington Florence PA 4 11 9 2 7 17 3 0 4421290006 Westmoreland Murrysville PA 4 3 5 2 1 9 2 0 4421290008 Westmoreland Greensburg PA *** *** 16 3 3 10 4 0 2Jamestown, NY (Classification: SUBPART 1)AQS MONITOR ID COUNTY MONITOR NAME ST8-hr Ozone exceedance days1997 1998 1999 2000 2001 2002 2003 2004 2005360130006 Chautauqua Dunkirk NY *** *** 12 5 11 23 7 4 6360130011 Chautauqua Westfield NY 4 11 8 3 4 18 4 0 2The Nature of the Ozone Air Quality Problem in the Northeast: A Conceptual Description Page C-11Hancock, Knox, Lincoln & Waldo Cos., ME (Classification: SUBPART 1)AQS MONITOR ID COUNTY MONITOR NAME ST8-hr Ozone exceedance days1997 1998 1999 2000 2001 2002 2003 2004 2005230130004 Knox Port Clyde ME 6 3 2 0 6 5 3 0 1230090401 Hancock Schoodic Point ME *** *** *** *** *** *** 1 0 ***230090001 Hancock Seawall ME *** *** *** 0 4 *** *** *** ***230090101 &230090103HancockAcadia National Park –McFarland HillME 1 4 5 0 9 6 2 0 0230090102 HancockAcadia National Park –Cadillac Mtn.ME 5 8 4 3 9 8 3 0 3Franklin Co., PA (Classification: SUBPART 1)AQS MONITOR ID COUNTY MONITOR NAME ST8-hr Ozone exceedance days1997 1998 1999 2000 2001 2002 2003 2004 2005420550001 Franklin Methodist Hill PA 7 22 20 4 15 27 3 0 0Erie, PA (Classification: SUBPART 1)AQS MONITOR ID COUNTY MONITOR NAME ST8-hr Ozone exceedance days1997 1998 1999 2000 2001 2002 2003 2004 2005420490003 Erie Erie PA 6 12 13 2 4 17 4 0 4Essex Co. (Whiteface Mtn.), NY (Classification: SUBPART 1)AQS MONITOR ID COUNTY MONITOR NAME ST8-hr Ozone exceedance days1997 1998 1999 2000 2001 2002 2003 2004 2005360310002Whiteface MountainSummitNY 2 1 3 2 5 12 7 0 ***360310003Essex (WhitefaceMountain above 1,900foot elevation )Whiteface Mtn. Base NY 1 2 3 0 3 11 5 0 1The Nature of the Ozone Air Quality Problem in the Northeast: A Conceptual Description Page C-12Allentown-Bethlehem-Easton, PA (Classification: SUBPART 1)AQS MONITOR ID COUNTY MONITOR NAME ST8-hr Ozone exceedance days1997 1998 1999 2000 2001 2002 2003 2004 2005420770004 Lehigh Allentown PA 12 18 19 5 9 16 4 3 6420950025 Northampton Freemansburg PA 0 5 22 6 14 12 4 6 5420950100 &420958000Northampton Easton PA 11 8 12 2 11 13 3 1 1Reading, PA (Classification: SUBPART 1)AQS MONITOR ID COUNTY MONITOR NAME ST8-hr Ozone exceedance days1997 1998 1999 2000 2001 2002 2003 2004 2005420110001 Berks Kutztown PA 6 14 12 2 7 11 1 *** ***420110009 &420110010Berks Reading PA 10 16 14 3 8 13 3 1 4Clearfield and Indiana Cos., PA(Classification: SUBPART 1)AQS MONITOR ID COUNTY MONITOR NAME ST8-hr Ozone exceedance days1997 1998 1999 2000 2001 2002 2003 2004 2005420630004 Indiana Strongstown PA *** *** *** *** *** *** *** *** 5420334000 Clearfield Moshannon PA 12 16 1 2 8 13 4 0 4Greene Co., PA (Classification: SUBPART 1)AQS MONITOR ID COUNTY MONITOR NAME ST8-hr Ozone exceedance days1997 1998 1999 2000 2001 2002 2003 2004 2005420590002 Greene Holbrook PA *** *** 21 6 12 9 3 0 5The Nature of the Ozone Air Quality Problem in the Northeast: A Conceptual Description Page C-13York, PA (Classification: SUBPART 1)AQS MONITOR ID COUNTY MONITOR NAME ST8-hr Ozone exceedance days1997 1998 1999 2000 2001 2002 2003 2004 2005420010002 Adams Biglerville PA *** *** *** *** *** 7 2 0 1421330008 York York PA 13 18 10 6 8 12 3 1 6Rochester, NY (Classification: SUBPART 1)AQS MONITOR ID COUNTY MONITOR NAME ST8-hr Ozone exceedance days1997 1998 1999 2000 2001 2002 2003 2004 2005360551004 &360551007Monroe Rochester NY 4 1 *** 1 3 12 3 0 0361173001 Wayne Williamson NY 4 4 7 1 5 10 2 0 0Albany-Schenectady-Troy, NY (Classification: SUBPART 1)AQS MONITOR ID COUNTY MONITOR NAME ST8-hr Ozone exceedance days1997 1998 1999 2000 2001 2002 2003 2004 2005360010012 Albany Albany – Loudonville NY 2 1 3 1 6 6 2 2 3360830004 Rensselaer Grafton State Park NY *** *** *** *** *** 16 2 2 2360910004 Saratoga Stillwater NY 3 2 6 1 7 6 5 2 3360930003 &360930093Schenectady Schenectady NY 1 0 2 1 1 3 2 0 0Harrisburg-Lebanon-Carlisle, PA (Classification: SUBPART 1)AQS MONITOR ID COUNTY MONITOR NAME ST8-hr Ozone exceedance days1997 1998 1999 2000 2001 2002 2003 2004 2005420430401 Dauphin Harrisburg PA 3 22 15 3 7 11 2 1 3420431100 Dauphin Hershey PA 9 9 15 5 12 13 2 0 4420990301 Perry Little Buffalo State Park PA 7 8 13 2 10 7 3 0 1The Nature of the Ozone Air Quality Problem in the Northeast: A Conceptual Description Page C-14Johnstown, PA (Classification: SUBPART 1)AQS MONITOR ID COUNTY MONITOR NAME ST8-hr Ozone exceedance days1997 1998 1999 2000 2001 2002 2003 2004 2005420210011 Cambria Johnstown PA 7 13 11 5 5 6 2 0 1Scranton-Wilkes-Barre, PA (Classification: SUBPART 1)AQS MONITOR ID COUNTY MONITOR NAME ST8-hr Ozone exceedance days1997 1998 1999 2000 2001 2002 2003 2004 2005420690101 Lackawanna Peckville PA 6 5 11 1 5 14 2 0 2420692006 Lackawanna Scranton PA 4 5 11 1 5 8 2 0 1420791100 Luzerne Nanticoke PA 0 2 4 1 5 6 3 0 0420791101 Luzerne Wilkes-Barre PA 8 7 9 1 7 7 2 0 1State College, PA (Classification: SUBPART 1)AQS MONITOR ID COUNTY MONITOR NAME ST8-hr Ozone exceedance days1997 1998 1999 2000 2001 2002 2003 2004 2005420270100 Centre State College PA *** *** *** 2 5 8 3 0 1420274000 Centre Penn Nursery PA 7 8 4 2 1 12 4 0 ***Tioga Co., PA (Classification: SUBPART 1)AQS MONITOR ID COUNTY MONITOR NAME ST8-hr Ozone exceedance days1997 1998 1999 2000 2001 2002 2003 2004 2005421174000 Tioga Tioga PA *** *** *** 2 3 8 3 0 0Altoona, PA (Classification: SUBPART 1)AQS MONITOR ID COUNTY MONITOR NAME ST8-hr Ozone exceedance days1997 1998 1999 2000 2001 2002 2003 2004 2005420130801 Blair Altoona PA 7 17 6 2 3 9 3 0 1The Nature of the Ozone Air Quality Problem in the Northeast: A Conceptual Description Page C-15Washington Co. (Hagerstown), MD (Classification: SUBPART 1 EARLY ACTION COMPACT)AQS MONITOR ID COUNTY MONITOR NAME ST8-hr Ozone exceedance days1997 1998 1999 2000 2001 2002 2003 2004 2005240430009 Washington Hagerstown MD *** *** 11 2 5 17 3 1 2New York (Classification: ATTAINMENT)AQS MONITOR ID COUNTY MONITOR NAME ST8-hr Ozone exceedance days1997 1998 1999 2000 2001 2002 2003 2004 2005360150003 Gloucester Elmira NY 0 2 2 1 2 4 1 0 0360410005 Hamilton Piseco Lake NY 1 1 1 1 2 4 2 0 1360430005 Herkimer Nicks Lake NY 0 0 0 1 0 1 2 0 0360530006 Madison Camp Georgetown NY 0 2 1 1 2 5 2 0 0360650004 Oneida Camden NY 0 1 1 1 3 5 2 0 0360671015 Onondaga East Syracuse NY 2 3 4 1 4 9 2 0 2360750003 Oswego Fulton NY *** *** *** *** *** *** 5 0 2361111005 Ulster Belleayre Mountain NY 4 1 3 1 3 1 3 0 0Maine (Classification: ATTAINMENT)AQS MONITOR ID COUNTY MONITOR NAME ST8-hr Ozone exceedance days1997 1998 1999 2000 2001 2002 2003 2004 2005230112005 Kennebec Gardiner ME 2 3 1 0 3 4 1 0 0230090301 Hancock Castine ME *** *** *** *** *** 3 1 0 0230210003 Piscataquis Dover-Foxcroft ME *** 0 1 0 0 *** *** *** ***230194008 Penobscot Holden ME 0 2 0 *** 6 4 1 0 0230173001 Oxford North Lovell ME 0 0 0 0 0 1 0 0 0CC0040002 NB CAN Roosevelt-Campobello IP NB 0 1 0 0 0 0 0 0 0230194007 Penobscot Howland ME 0 0 1 0 0 1 0 0 0230038001 Aroostook Ashland ME 0 0 0 0 0 1 0 0 0The Nature of the Ozone Air Quality Problem in the Northeast: A Conceptual Description Page C-16Pennsylvania (Classification: ATTAINMENT)AQS MONITOR ID COUNTY MONITOR NAME ST8-hr Ozone exceedance days1997 1998 1999 2000 2001 2002 2003 2004 2005420730015 Lawrence New Castle PA 4 2 5 0 1 6 2 0 1420810100 Lycoming Montoursville PA *** *** *** *** *** 7 3 0 3420810403 Lycoming Williamsport PA 0 1 0 1 1 *** *** *** ***420814000 Lycoming Tiadaghton PA 0 3 0 1 1 3 2 0 ***Vermont (Classification: ATTAINMENT)AQS MONITOR ID COUNTY MONITOR NAME ST8-hr Ozone exceedance days1997 1998 1999 2000 2001 2002 2003 2004 2005500030004 Bennington Bennington VT 2 0 3 1 2 4 0 2 0500070007 Chittenden Underhill VT 0 0 1 0 0 3 0 0 0New Hampshire (Classification: ATTAINMENT)AQS MONITOR ID COUNTY MONITOR NAME ST8-hr Ozone exceedance days1997 1998 1999 2000 2001 2002 2003 2004 2005330012003 &330012004Belknap Laconia NH 1 0 0 *** 2 3 0 0 0330031002 Carroll Conway NH 0 0 0 0 0 1 *** *** ***330050007 Cheshire Keene NH 1 1 1 1 1 1 0 0 0330074002 Coos Mt Washington Base NH *** *** *** *** *** 0 0 1 0330074003 Coos Pittsburg NH *** *** *** *** *** *** 0 0 0330090008 &330092005Grafton Haverhill-Lebanon NH 0 0 0 0 0 1 0 0 0330115001 HillsboroughPeterborough (Miller StatePark)NH *** *** *** *** *** *** 0 1 3330170007 &330171007Strafford Concord NH 1 0 0 0 1 4 0 1 0330190003 Sullivan Claremont NH 1 0 0 1 0 3 0 1 0DRAFT – The Nature of the Ozone Air Quality Problem in the Northeast: A Conceptual Description Page D-1



# Appendix D: 8-hour ozone design values in the OTR, 1997-2005DRAFT –The Nature of the Ozone Air Quality Problem in theNortheast: A Conceptual Description Page D-2Appendix D: 8-hour ozone designvalues in the OTR, 1997-2005Tables of the valid 8-hour ozone design values (3-year averages of the ozone season 4thmaximum 8-hour ozone concentrations)recorded at individualmonitors in OTR nonattainment/attainment areas for the 1997-2005 ozone seasons. Hourly data weredownloaded from the USEPA Air Quality System (AQS) databasein January 2006. The 8-hour averages and design values werecalculated using procedures specified in EPA’s “Guideline on Data Handling Conventions for the 8-hourOzone NAAQS” (OAQPS,EPA-454/R-98-017, Dec. 1998) with flagged data (due to a regional forest fire smokeevent) eliminated from the analysis. “***”indicates years during which a monitor wasnot in operation or had less than 90 percent data collection (with a design value less than85 ppb) for the respective 3-year period. Red shading indicates averages≥85 ppb (violating the 8-hr ozone NAAQS), orange shadingindicates averages between 80 and 84 ppb,yellow shading indicates average between75 and 79 ppb and green shading indicatesaverages < 75 ppb. While these tables are derived from the publicly available data downloaded inJanuary 2006 from the USEPA AQSdatabase, states may have monitoring data that differ from these.For example, design values for New Jersey were provided by theNew Jersey Department of Environmental Protection and differ in some instances fromthe derived values based on the USEPA AQSdatabase.Philadelphia-Wilmington-Atlantic City, PA-NJ-MD-DE (Classification: MODERATE) 8-hr Ozone DESIGN VALUE (ppb)AQS MONITOR ID COUNTY MONITOR NAME ST1997-19991998-20001999-20012000-20022001-20032002-20042003-2005100010002 Kent Killens Pond DE99979392898480100031003 New Castle Bellefonte DE90919192*** *** ***100031007 New Castle Lums Pond DE100979796938480100031010 New Castle Brandywine Creek DE99969596938982100031013 New Castle Wilmington (Bellefonte2) DE *** *** *** ***908582100051002 Sussex Seaford DE99989594918582100051003 Sussex Lewes DE ***959087888584240150003 Cecil Fairhill MD110106106104989189340010005 Atlantic Nacote Creek NJ101949591918582340070003 Camden Camden Lab NJ1041011041011029385340071001 Camden Ancora NJ1111061081041029692340110007 Cumberland Millville NJ10410110298989186340150002 Gloucester Clarksboro NJ1061051051041009488340210005 Mercer Rider Univ. NJ112109112102999185DRAFT –The Nature of the Ozone Air Quality Problem in theNortheast: A Conceptual Description Page D-3Philadelphia-Wilmington-Atlantic City, PA-NJ-MD-DE (Classification: MODERATE) 8-hr Ozone DESIGN VALUE (ppb)AQS MONITOR ID COUNTY MONITOR NAME ST1997-19991998-20001999-20012000-20022001-20032002-20042003-2005340290006 Ocean Colliers Mills NJ1131141151131099994420170012 Bucks Bristol PA1031021051041009386420290050 Chester West Chester PA *** *** *** ***95*** ***420290100 Chester New Garden PA *** *** ***95989187420450002 Delaware Chester PA100969495928882420910013 Montgomery Norristown PA10410210097928886421010004 Philadelphia Philadelphia – Downtown PA72727174756863421010014 Philadelphia Philadelphia – Roxborough PA90878893938681421010024 Philadelphia Philadelphia– NE Airport PA *** *** ***98979590421010136 Philadelphia Philadelphia – Elmwood PA868988878480 ***Baltimore, MD (Classification: MODERATE) 8-hr OzoneDESIGN VALUE (ppb) 8-hr Ozone DESIGN VALUE (ppb)AQS MONITOR ID COUNTY MONITOR NAME ST1997-19991998-20001999-20012000-20022001-20032002-20042003-2005240030014 Anne Arundel Davidsonville MD109107103102989489240030019 Anne Arundel Fort Meade MD1071001001019793***240051007 Baltimore Padonia MD95929392898577240053001 Baltimore Essex MD99939393938883240130001 Carroll South Carroll MD95949392898582240251001 Harford Edgewood MD1051001041041039491240259001 Harford Aldino MD1069798100989386245100053 Baltimore (City) Baltimore-Ponca St MD *** *** *** *** *** *** ***245100050 Baltimore (City) Baltimore-0050 MD *** *** *** *** *** *** ***245100051 Baltimore (City) Baltimore-0051 MD90*** *** *** *** *** ***New York-N. New Jersey-Long Island, NY-NJ-CT (Classification: MODERATE) 8-hr Ozone DESIGN VALUE (ppb)AQS MONITOR ID COUNTY MONITOR NAME ST1997-19991998-20001999-20012000-20022001-20032002-20042003-200590010017 Fairfield Greenwich CT99939695100928790011123 Fairfield Danbury CT101969798969391DRAFT –The Nature of the Ozone Air Quality Problem in theNortheast: A Conceptual Description Page D-4New York-N. New Jersey-Long Island, NY-NJ-CT (Classification: MODERATE) 8-hr Ozone DESIGN VALUE (ppb)AQS MONITOR ID COUNTY MONITOR NAME ST1997-19991998-20001999-20012000-20022001-20032002-20042003-200590013007 Fairfield Stratford CT98949698102959090019003 Fairfield Westport CT10394979397928990010113 Fairfield Bridgeport CT *** *** *** *** *** *** ***90070007 Middlesex Middletown CT9995999798929090091123 &90090027New Haven New Haven CT86*** *** *** *** *** ***90093002 New Haven Madison CT103969798102959090099005 New Haven Hamden CT *** ***959498*** ***340030005 Bergen Teaneck NJ *** *** ***92958986340030001 Bergen Cliffside Park NJ *** *** *** *** *** *** ***340130011 &340130016Essex Newark Lab NJ93*** *** *** *** *** ***340170006 Hudson Bayonne NJ1079910086878284340190001 Hunterdon Flemington NJ10610310497979290340230011 Middlesex Rutgers Univ. NJ113109111101988986340250005 Monmouth Monmouth Univ. NJ10010210197979389340273001 Morris Chester NJ10210010198989082340315001 Passaic Ramapo NJ ***899488888481340390008 Union Plainfield NJ *** *** *** *** *** *** ***360050080 Bronx NYC-Morrisania Center NY84 *** *** *** *** *** ***360050083 Bronx NYC-200thSt & Southern Blvd NY88808381848375360050110 Bronx NYC-IS52 NY *** *** *** *** ***8076360610010 New York NYC-Mabel Dean HS NY ***69 *** *** *** *** ***360610063 New York NYC-Roof WTC NY1069898*** *** *** ***360810004 Queens NYC-Queens College NY *** *** *** *** *** *** ***360810097 Queens NYC-QBORO NY ***8886*** *** *** ***360810098 Queens NYC-College Pt NY *** ***6874757269360810124 Queens NYC-Queens NY *** *** *** *** *** *** ***360850067 Richmond NYC-Susan Wagner HS NY105969896948987361030002 Suffolk Babylon NY97918792959491DRAFT –The Nature of the Ozone Air Quality Problem in theNortheast: A Conceptual Description Page D-5New York-N. New Jersey-Long Island, NY-NJ-CT (Classification: MODERATE) 8-hr Ozone DESIGN VALUE (ppb)AQS MONITOR ID COUNTY MONITOR NAME ST1997-19991998-20001999-20012000-20022001-20032002-20042003-2005361030004 Suffolk Riverhead NY98949185*** *** ***361030009 Suffolk Holtsville NY *** *** ***9710094***361192004 Westchester White Plains NY98929290949088Washington, DC-MD-VA (Classification: MODERATE) 8-hr Ozone DESIGN VALUE (ppb)AQS MONITOR ID COUNTY MONITOR NAME ST1997-19991998-20001999-20012000-20022001-20032002-20042003-2005110010025District of Columbia(all)Takoma DC95969393888578110010041District of Columbia(all)River Terrace DC91888891928477110010043District of Columbia(all)McMillian Reservoir DC100969495948982240090010 &240090011Calvert Calvert MD909189*** *** *** ***240170010 Charles S. Maryland MD1041019694949188240210037 Frederick Frederick Municipal Airport MD ***929191888378240313001 Montgomery Rockville MD95908989888380240330002 Prince George's Greenbelt MD10699979593*** ***240338001 Prince George's Suitland MD999493*** *** *** ***240338003 Prince George's Equestrian Center MD *** *** *** *** ***9491510130020 Arlington Co Aurora Hills VA97929296999587510590005 Fairfax Chantilly (Cub Run) VA91918888898479510590018 Fairfax Mount Vernon VA96979597979691510590030 Fairfax Franconia VA ***908992979689510591004 &510591005Fairfax Seven Corners & Annandale VA9590*** *** ***9486510595001 Fairfax McLean – Lewinsville VA86868690888679511071005 Loudoun Ashburn VA ***8986909288***511530009 Prince William James S. Long PARK VA91888585878379515100009 Alexandria (City) Alexandria VA91898890928881DRAFT –The Nature of the Ozone Air Quality Problem in theNortheast: A Conceptual Description Page D-6Jefferson Co., NY (Classification: MODERATE) 8-hr Ozone DESIGN VALUE (ppb)AQS MONITOR ID COUNTY MONITOR NAME ST1997-19991998-20001999-20012000-20022001-20032002-20042003-2005360450002 Jefferson Perch River NY90828791978681Greater Connecticut, CT (Classification: MODERATE) 8-hr Ozone DESIGN VALUE (ppb)AQS MONITOR ID COUNTY MONITOR NAME ST1997-19991998-20001999-20012000-20022001-20032002-20042003-200590031003 Hartford East Hartford CT9184889090848090050005 Litchfield Cornwall (Mohawk Mt) CT *** *** *** *** ***898790050006 Litchfield Torrington CT9793*** *** *** *** ***90110008 New London Groton CT9487908993888590131001 Tolland Stafford CT95899094958886Boston-Lawrence-Worcester (E. MA), MA (Classification: MODERATE) 8-hr Ozone DESIGN VALUE (ppb)AQS MONITOR ID COUNTY MONITOR NAME ST1997-19991998-20001999-20012000-20022001-20032002-20042003-2005250010002 Barnstable Truro MA95899693958886250051002 Bristol Fairhaven MA91879390958886250051005 Bristol Easton MA888184 *** *** *** ***250070001 DukesWampanoag Laboratory –Martha’s VineyardMA *** *** *** *** *** *** ***250095005 Essex Lawrence-Haverhill MA74686370 *** *** ***250092006 Essex Lynn MA93868690938783250094004 Essex Newbury MA87828386898378250170009 MiddlesexUSEPA Region 1 Lab –ChelmsfordMA *** *** *** *** *** *** ***250171102 Middlesex Stow MA ***868889897975250171801 Middlesex Sudbury MA *** *** *** *** *** *** ***250174003 Middlesex Waltham MA93*** *** *** *** *** ***250213003 Norfolk E Milton (Blue Hill) MA *** *** *** *** ***9185250250041 Suffolk Boston-Long Island MA *** ***8489918681250250042 Suffolk Boston-Roxbury MA *** ***6672767168250251003 Suffolk Chelsea MA82 *** *** *** *** *** ***250270015 Worcester Worcester MA9488858586***79DRAFT –The Nature of the Ozone Air Quality Problem in theNortheast: A Conceptual Description Page D-7Providence (All RI), RI (Classification:MODERATE) 8-hr Ozone DESIGN VALUE (ppb)AQS MONITOR ID COUNTY MONITOR NAME ST1997-19991998-20001999-20012000-20022001-20032002-20042003-2005440030002 Kent W Greenwich RI92889497958784440071010 Providence E Providence RI *** ***879193***82440090007 Washington Narragansett RI ***859293959089Springfield (Western MA), MA (Classification: MODERATE) 8-hr Ozone DESIGN VALUE (ppb)AQS MONITOR ID COUNTY MONITOR NAME ST1997-19991998-20001999-20012000-20022001-20032002-20042003-2005250034002 Berkshire Adams MA *** *** *** ***87*** ***230130003 Hampden Agawam MA84777783 *** *** ***250130008 Hampden Chicopee MA91868592949084250150103 Hampshire South Hadley (Amherst) MA82767778776967250154002 Hampshire Ware MA99898989878482Poughkeepsie, NY (Classification: MODERATE) 8-hr Ozone DESIGN VALUE (ppb)AQS MONITOR ID COUNTY MONITOR NAME ST1997-19991998-20001999-20012000-20022001-20032002-20042003-2005360270007 Dutchess Millbrook NY90878793948979360715001 Orange Valley Central NY90868784878384360790005 Putnam Mt Ninham NY94898992938986Boston-Manchester-Portsmouth (SE), NH (Classification: MODERATE) 8-hr Ozone DESIGN VALUE (ppb)AQS MONITOR ID COUNTY MONITOR NAME ST1997-19991998-20001999-20012000-20022001-20032002-20042003-2005330110016 &330110019 &330110020Hillsborough Manchester NH *** *** *** *** ***7570330111010 &330111011Hillsborough Nashua NH89818385878480DRAFT –The Nature of the Ozone Air Quality Problem in theNortheast: A Conceptual Description Page D-8Boston-Manchester-Portsmouth (SE), NH (Classification: MODERATE) 8-hr Ozone DESIGN VALUE (ppb)AQS MONITOR ID COUNTY MONITOR NAME ST1997-19991998-20001999-20012000-20022001-20032002-20042003-2005330150009 &330150015 &330150014Rockingham Portsmouth NH8780 *** *** ***8075330150013 Rockingham Brentwood NH ***697680 *** *** ***330150012 &330150016Rockingham Rye NH90798183847873330173002 Strafford Rochester NH8176757780 *** ***Kent and Queen Anne’s Cos., MD (Classification:MARGINAL) 8-hr Ozone DESIGN VALUE (ppb)AQS MONITOR ID COUNTY MONITOR NAME ST1997-19991998-20001999-20012000-20022001-20032002-20042003-2005240290002 Kent Millington MD100101100102958982Lancaster, PA (Classification: MARGINAL) 8-hr Ozone DESIGN VALUE (ppb)AQS MONITOR ID COUNTY MONITOR NAME ST1997-19991998-20001999-20012000-20022001-20032002-20042003-2005420710007 Lancaster Lancaster PA101979694928683Portland, ME (Classification: MARGINAL) 8-hr Ozone DESIGN VALUE (ppb)AQS MONITOR ID COUNTY MONITOR NAME ST1997-19991998-20001999-20012000-20022001-20032002-20042003-2005230050027 Cumberland Portland ME *** *** *** *** *** *** ***230052003 Cumberland Cape Elizabeth ME89778086887971230230003 &230230004SagadahocPhippsburg/Georgetown (ReidState Park)ME9284 *** *** ***7970230313002 York Kittery ME88818184888477230312002 York Kennebunkport ME92828690918474230310037 &230310038York Hollis ME7672 *** *** ***7573DRAFT –The Nature of the Ozone Air Quality Problem in theNortheast: A Conceptual Description Page D-9Buffalo-Niagara Falls, NY (Classification:SUBPART 1) 8-hr Ozone DESIGN VALUE (ppb)AQS MONITOR ID COUNTY MONITOR NAME ST1997-19991998-20001999-20012000-20022001-20032002-20042003-2005360290002 Erie Amherst NY85899297999186360631006 Niagara Middleport NY86858791958986Youngstown-Warren-Sharon, OH-PA (Classification: SUBPART 1) 8-hr Ozone DESIGN VALUE (ppb)AQS MONITOR ID COUNTY MONITOR NAME ST1997-19991998-20001999-20012000-20022001-20032002-20042003-2005390990009 &390990013Mahoning Youngstown - Oakhill OH91898687898580391550008 &391550011Trumbull Warren-Trumbull County OH95918890959186391550009 Trumbull Kinsman OH95918787908783420850100 Mercer Farrell PA96928892948883Pittsburgh-Beaver Valley, PA (Classification:SUBPART 1) 8-hr Ozone DESIGN VALUE (ppb)AQS MONITOR ID COUNTY MONITOR NAME ST1997-19991998-20001999-20012000-20022001-20032002-20042003-2005420030008 Allegheny Lawrenceville PA91888589928781420030010 Allegheny Pittsburg PA ***919293938684420030067 Allegheny South Fayette PA99969090918782420030088 Allegheny Penn Hills PA929188*** *** *** ***420031005 Allegheny Harrison Township PA101949295928781420050001 Armstrong Kittanning PA86939291938884420070002 Beaver Hookstown PA92898890949084420070005 Beaver Brighton Township PA91908990928781420070014 Beaver Beaver Falls PA90898588868175421250005 Washington Charleroi PA101948786898480421250200 Washington Washington PA91888686888281421255001 Washington Florence PA91908888878278421290006 Westmoreland Murrysville PA85818081848180421290008 Westmoreland Greensburg PA *** ***8686918782DRAFT –The Nature of the Ozone Air Quality Problem in theNortheast: A Conceptual Description Page D-10Jamestown, NY (Classification: SUBPART 1) 8-hr Ozone DESIGN VALUE (ppb)AQS MONITOR ID COUNTY MONITOR NAME ST1997-19991998-20001999-20012000-20022001-20032002-20042003-2005360130006 Chautauqua Dunkirk NY *** ***8992949389360130011 Chautauqua Westfield NY89888587898579Hancock, Knox, Lincoln & Waldo Cos., ME (Classification: SUBPART 1)AQS MONITOR ID COUNTY MONITOR NAME ST1997-19991998-20001999-20012000-20022001-20032002-20042003-2005230130004 Knox Port Clyde ME82768083878177230090401 Hancock Schoodic Point ME *** *** *** *** *** *** ***230090001 Hancock Seawall ME *** *** *** *** *** *** ***230090101 &230090103HancockAcadia National Park -McFarland HillME85838584878075230090102 HancockAcadia National Park -Cadillac Mtn.ME89878993948882Franklin Co., PA (Classification: SUBPART 1) 8-hr Ozone DESIGN VALUE (ppb)AQS MONITOR ID COUNTY MONITOR NAME ST1997-19991998-20001999-20012000-20022001-20032002-20042003-2005420550001 Franklin Methodist Hill PA97959294938575Erie, PA (Classification: SUBPART 1)8-hr Ozone DESIGN VALUE (ppb)AQS MONITOR ID COUNTY MONITOR NAME ST1997-19991998-20001999-20012000-20022001-20032002-20042003-2005420490003 Erie Erie PA93908788928783Essex Co. (Whiteface Mtn.), NY (Classification: SUBPART 1) 8-hr Ozone DESIGN VALUE (ppb)AQS MONITOR ID COUNTY MONITOR NAME ST1997-19991998-20001999-20012000-20022001-20032002-20042003-2005360310002 Whiteface Mountain Summit NY80 *** ***879189***360310003Essex (WhitefaceMountain above 1,900foot elevation )Whiteface Mtn. Base NY79767882888377DRAFT –The Nature of the Ozone Air Quality Problem in theNortheast: A Conceptual Description Page D-11Allentown-Bethlehem-Easton, PA (Classification:SUBPART 1) 8-hr Ozone DESIGN VALUE (ppb)AQS MONITOR ID COUNTY MONITOR NAME ST1997-19991998-20001999-20012000-20022001-20032002-20042003-2005420770004 Lehigh Allentown PA100979693918885420950025 Northampton Freemansburg PA87959792908887420950100 &420958000Northampton Easton PA93909189898682Reading, PA (Classification: SUBPART 1) 8-hr Ozone DESIGN VALUE (ppb)AQS MONITOR ID COUNTY MONITOR NAME ST1997-19991998-20001999-20012000-20022001-20032002-20042003-2005420110001 Berks Kutztown PA9289908784 *** ***420110009 &420110010Berks Reading PA96929592918380Clearfield and Indiana Cos., PA (Classification:SUBPART 1) 8-hr Ozone DESIGN VALUE (ppb)AQS MONITOR ID COUNTY MONITOR NAME ST1997-19991998-20001999-20012000-20022001-20032002-20042003-2005420630004 Indiana Strongstown PA *** *** *** *** *** *** ***420334000 Clearfield Moshannon PA93878387908582Greene Co., PA (Classification: SUBPART 1) 8-hr Ozone DESIGN VALUE (ppb)AQS MONITOR ID COUNTY MONITOR NAME ST1997-19991998-20001999-20012000-20022001-20032002-20042003-2005420590002 Greene Holbrook PA97969290898481York, PA (Classification: SUBPART 1) 8-hr Ozone DESIGN VALUE (ppb)AQS MONITOR ID COUNTY MONITOR NAME ST1997-19991998-20001999-20012000-20022001-20032002-20042003-2005420010002 Adams Biglerville PA *** *** *** *** ***8076421330008 York York PA94939092898682DRAFT –The Nature of the Ozone Air Quality Problem in theNortheast: A Conceptual Description Page D-12Rochester, NY (Classification: SUBPART 1) 8-hr Ozone DESIGN VALUE (ppb)AQS MONITOR ID COUNTY MONITOR NAME ST1997-19991998-20001999-20012000-20022001-20032002-20042003-2005360551004 &360551007Monroe Rochester NY *** *** ***85887973361173001 Wayne Williamson NY86818183888171Albany-Schenectady-Troy, NY (Classification:SUBPART 1) 8-hr Ozone DESIGN VALUE (ppb)AQS MONITOR ID COUNTY MONITOR NAME ST1997-19991998-20001999-20012000-20022001-20032002-20042003-2005360010012 Albany Albany - Loudonville NY80778083868076360830004 Rensselaer Grafton State Park NY *** *** *** *** ***8680360910004 Saratoga Stillwater NY848084 ***878482360930003 &360930093Schenectady Schenectady NY75717576817674Harrisburg-Lebanon-Carlisle, PA (Classification:SUBPART 1) 8-hr Ozone DESIGN VALUE (ppb)AQS MONITOR ID COUNTY MONITOR NAME ST1997-19991998-20001999-20012000-20022001-20032002-20042003-2005420430401 Dauphin Harrisburg PA92908687868278420431100 Dauphin Hershey PA94939491888178420990301 Perry Little Buffalo State Park PA90858483878078Johnstown, PA (Classification: SUBPART 1) 8-hr Ozone DESIGN VALUE (ppb)AQS MONITOR ID COUNTY MONITOR NAME ST1997-19991998-20001999-20012000-20022001-20032002-20042003-2005420210011 Cambria Johnstown PA93918888878077DRAFT –The Nature of the Ozone Air Quality Problem in theNortheast: A Conceptual Description Page D-13Scranton-Wilkes-Barre, PA (Classification: SUBPART 1) 8-hr Ozone DESIGN VALUE (ppb)AQS MONITOR ID COUNTY MONITOR NAME ST1997-19991998-20001999-20012000-20022001-20032002-20042003-2005420690101 Lackawanna Peckville PA90878685858075420692006 Lackawanna Scranton PA88848483847976420791100 Luzerne Nanticoke PA82818283847873420791101 Luzerne Wilkes-Barre PA92848484868177State College, PA (Classification: SUBPART 1) 8-hr Ozone DESIGN VALUE (ppb)AQS MONITOR ID COUNTY MONITOR NAME ST1997-19991998-20001999-20012000-20022001-20032002-20042003-2005420270100 Centre State College PA *** *** ***85868279420274000 Centre Penn Nursery PA908480828884 ***Tioga Co., PA (Classification: SUBPART 1) 8-hr Ozone DESIGN VALUE (ppb)AQS MONITOR ID COUNTY MONITOR NAME ST1997-19991998-20001999-20012000-20022001-20032002-20042003-2005421174000 Tioga Tioga PA *** *** ***84868581Altoona, PA (Classification: SUBPART 1)8-hr Ozone DESIGN VALUE (ppb)AQS MONITOR ID COUNTY MONITOR NAME ST1997-19991998-20001999-20012000-20022001-20032002-20042003-2005420130801 Blair Altoona PA95898484858177Washington Co. (Hagerstown), MD (Classification: SUBPART 1) 8-hr Ozone DESIGN VALUE (ppb)AQS MONITOR ID COUNTY MONITOR NAME ST1997-19991998-20001999-20012000-20022001-20032002-20042003-2005240430009 Washington Hagerstown MD *** ***8587868378DRAFT –The Nature of the Ozone Air Quality Problem in theNortheast: A Conceptual Description Page D-14New York (Classification: ATTAINMENT) 8-hr Ozone DESIGN VALUE (ppb)AQS MONITOR ID COUNTY MONITOR NAME ST1997-19991998-20001999-20012000-20022001-20032002-20042003-2005360150003 Gloucester Elmira NY79797981837770360410005 Hamilton Piseco Lake NY79777779817673360430005 Herkimer Nicks Lake NY72707274767269360530006 Madison Camp Georgetown NY79787880827773360650004 Oneida Camden NY76737678837872360671015 Onondaga East Syracuse NY8280818385***74360750003 Oswego Fulton NY *** *** *** *** *** ***82361111005 Ulster Belleayre Mountain NY83808181838079Maine (Classification: ATTAINMENT) 8-hr Ozone DESIGN VALUE (ppb)AQS MONITOR ID COUNTY MONITOR NAME ST1997-19991998-20001999-20012000-20022001-20032002-20042003-2005230112005 Kennebec Gardiner ME77737578807670230090301 Hancock Castine ME *** *** *** *** ***7570230210003 Piscataquis Dover-Foxcroft ME ***6265 *** *** *** ***230194008 Penobscot Holden ME75 ***76 ***837568230173001 Oxford North Lovell ME59586160626061CC0040002 NB CAN Roosevelt-Campobello IP NB62606160615454230194007 Penobscot Howland ME71686968686461230038001 Aroostook Ashland ME65626465646360Pennsylvania (Classification: ATTAINMENT) 8-hr Ozone DESIGN VALUE (ppb)AQS MONITOR ID COUNTY MONITOR NAME ST1997-19991998-20001999-20012000-20022001-20032002-20042003-2005420730015 Lawrence New Castle PA83787878807773420810100 Lycoming Montoursville PA *** *** *** *** ***8279420810403 Lycoming Williamsport PA747171 *** *** *** ***420814000 Lycoming Tiadaghton PA ***7776798077 ***DRAFT –The Nature of the Ozone Air Quality Problem in theNortheast: A Conceptual Description Page D-15Vermont (Classification: ATTAINMENT) 8-hr Ozone DESIGN VALUE (ppb)AQS MONITOR ID COUNTY MONITOR NAME ST1997-19991998-20001999-20012000-20022001-20032002-20042003-2005500030004 Bennington Bennington VT80767980807873500070007 Chittenden Underhill VT74747577787671New Hampshire (Classification: ATTAINMENT) 8-hr Ozone DESIGN VALUE (ppb)AQS MONITOR ID COUNTY MONITOR NAME ST1997-19991998-20001999-20012000-20022001-20032002-20042003-2005330012003 &330012004Belknap Laconia NH68 *** *** ***787573330031002 Carroll Conway NH67646667 *** *** ***330050007 Cheshire Keene NH75717273767471330074002 Coos Mt Washington Base NH *** *** *** *** *** ***67330074003 Coos Pittsburg NH *** *** *** *** *** ***60330090008 &330092005Grafton Haverhill-Lebanon NH70706968727271330115001 HillsboroughPeterborough (Miller StatePark)NH *** *** *** *** *** ***77330170007 &330171007Strafford Concord NH74717074757571330190003 Sullivan Claremont NH73707273757772The Nature of the Ozone Air Quality Problem in the Northeast: A Conceptual Description Page E-1



# Appendix E: The sea breeze and flow over the ocean in-depthThe Nature of the Ozone Air Quality Problem in the Northeast: A Conceptual Description Page E-2



# Appendix E: The sea breeze and fl ow over the ocean in-depth

Figure E-1 displays a general descripti on of ozone transport in coastal New England. This figure shows 90 th 

### percentile ozone concentrat ion wind direction plots at four sites along the coast. For the first si te, Lynn, MA, high ozone days are affected mainly by winds from the southwest bringi ng ozone up the coast to the site. At the second site, Newbury, MA, winds arrive to the s ite from two directions, up the coast, in a similar pattern seen at Lynn, but also from the ocean. The high ozone days therefore can result from ozone and its precursors coming from inland or from the ocean in the sea breeze. At the two northern sites in Maine, Cape Elizabeth and Acadia National Park, winds on high ozone days come mostly off the ocean. This is mainly due to the orientation of the Maine coastline, as summertime winds generally come from the southwest, therefore traveling over the ocean before arriving to these sites.

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Figure E-1. 90th percentile ozone concentration wind direction frequency plots at four coastal sites in northern New England (figure provided by Tom Downs, Maine Department of Environmental Protection).



### Figure E-2 displays wind directions at Newbury, MA on June 29, 1997 where hourly ozone concentrations ranged from 88 ppb to 107 ppb during the afternoon hours

and a sea breeze can be identified. The forward trajectory starting in Boston at 6 a.m. shows winds pushing air from the Boston metr o area out into the harbor throughout the day. The hourly ozone wind rose at Newbury, MA shows the afternoon wind shift thatThe Nature of the Ozone Air Quality Problem in the Northeast: A Conceptual Description Page E-3



### occurred on this day where vector direc tion indicates wind dir ection and magnitude indicates ozone concentrations. Morning winds came from a west/northwesterly direction when hourly ozone concentrations at the site ranged from 47 to 68 ppb. At 1 p.m., the wind shifted direction, now coming off the ocean from the southeast, accompanied by a 20 ppb increase in hourly ozone. Hourly ozone levels then continue d to increase in the early afternoon, peaking at 107 ppb at 3 p.m. This increase in ozone levels accompanying a shift in winds pushing air masses from the ocea n to a coastal site illustrates how the sea breeze can contribute to poor air quality along th e coast. The poor air quality could be a result of polluted air from Boston being pushe d back to the site in the sea breeze. Sea breezes, however, are not always associated with worsening air quality as the afternoon sea breeze doesn’t always bring in polluted air.

6AM-12PM

1PM-5PM

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### Boston, MA

Newbury, MA

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### Boston, MA

Newbury, MA

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Figure E-2. Example of a se a breeze effect occurring in Newbury, MA on June 29, 1997 (figure data provided by Tom Downs, Maine Department of Environmental Protection).



### At sites further north in Maine, the sea br eeze effect is less dramatic due to the orientation of the Maine coastline. Figure E- 3 shows a similar ozone wind rose plot for Cape Elizabeth, ME on the same day illustrated in Figure E-2. With the exception of the

winds at 6 a.m. that came from the northwest , the winds arrived to the site from the southwest direction. There are some slight sh ifts in wind direction, particularly a shift after 5 p.m. that began to bring winds from the inland side of the coast, but it is difficult

to determine whether these shifts are due to a sea breeze effect or if the evening shift is due to the weakened sea breeze. Winds are generally moving up the coast, over water,

and winds in the same direction of the sea br eeze can bring poor air quality. On this day, ozone concentrations ranged between 89 and 102 ppb between 3 p.m. and 7 p.m.The Nature of the Ozone Air Quality Problem in the Northeast: A Conceptual Description Page E-4

0 0.02 0.04 0.06 0.08 0.1 0.12

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Boston, MA 6AM-12PM

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### Cape Elizabeth, ME

Boston, MA 6AM-12PM

1PM-4PM

5PM-6PM

Figure E-3. Wind directions and ozone concentrations at Cape Elizabeth, ME on June 29, 1997 (figure data provided by Tom Downs, Maine Department of Environmental Protection).



### Transport over the ocean is commonly observed downwind of the New York City metropolitan area during the summer months due its proximity to the Atlantic Ocean and the Long Island Sound. The four pollution rose plots presented in Figure E-4 represent the frequency of wind direction on the highe st 10 percentile ozone concentration days from April 1 to October 31 during the y ears 1997 to 2005. The winds on the highest ozone days point at the New York City metropolitan area at all locations along the Connecticut shoreline. Going along the Conn ecticut shoreline to the east (towards Groton), the predominant wind frequency dir ection shifts increasingly to the west, tracking the upwind location of the New York City metropolitan area.The Nature of the Ozone Air Quality Problem in the Northeast: A Conceptual Description Page E-5

Figure E-4. Wind rose plots along Connecticut shoreline for the time period April 1 to October 31 during the years 1997 through 2005. The elongated red outlines pointing to the southwest to west are wind directions on the highest 10 percentile ozone concentration days at four Connecticut coastal locations. For comparison, the blue outlines are the wind rose plots fo r all days over the same period. The high ozone day wind rose plots indicate pollution flow over Long Island Sound that tracks the upwind location of the New York City metropolitan area (figure from Tom Do wns, Maine Department of the Environment). Each plot shows frequency of high ozone increases as the wind points up LIS

towards emission-rich areas

of the Northeast corridor.The Nature of the Ozone Air Quality Problem in the Northeast: A Conceptual Description Page F-1



# Appendix F: Observed nocturnal low level jet across the OTR, July 2002The Nature of the Ozone Air Quality Problem in the Northeast: A Conceptual Description Page F-2



# Appendix F: Observed nocturnal low level jet across the OTR, July 2002

An example of the nocturnal low level jet across the OTR can be seen on the nights of July 22 through July 24, 2002, as night time winds at altitudes between 450 m

and 1500 m were observed at several coastal sites. Figure F-1 shows wind profiler data on the night of July 22-July 23, 2002 for five sites along the east co ast: Fort Meade, MD (FME), Orange, MA (ORE), Stow, MA (STW), Appledore Island, ME (ADI), and Pease Air Force Base, NH (PSE). These wind “barb” plots show wind direction (direction of arrow indicating where wind is coming from), wind speed (wind barb color), time of day (UTC time, x-axis), and altit ude (meters, y-axis). The locat ion of the nocturnal low level jet appears within the circle in each wind ba rb plot of Figure F-1. The figure shows a weak nocturnal low level jet at the southernmost site, Fort Meade, with wind speeds of 15

to 25 knots between 300 m and 500 m in the ear ly part of the night. Further north, the nocturnal low level jet is more pronounced with wind speeds between 500 m and 1500 m above ground reaching 40 knots. Figure F-1 shows on this day the nocturnal low level jet extending from Maryland up through southern Ma ine. In addition, the wind barb plots show the northeasterly direction of the nocturn al low level jet. Above this jet, we see slower winds coming from the west to all the sites.The Nature of the Ozone Air Quality Problem in the Northeast: A Conceptual Description Page F-3

7.22.02-7.23.02 FME ORE STW ADI PSE

Direction of

LLJ

7.22.02-7.23.02 FME ORE STW ADI PSE

Direction of

LLJ

Figure F-1. Nocturnal low level jet on July 22 – 23, 2002. Note: Circles in the wind barb plots indicate the location of the nocturnal low level jet.



### Figure F-1 shows that throughout the night, th e nocturnal low level jet travels in a northeasterly direction along the east coast. Th e pollution implications of this nocturnal low level jet episode can be seen in Figure F-2. The Cadillac Mountain ozone monitor is

located on the coast of Maine at an elevation of 466 m. At th is elevated position, we can see how the nocturnal low level jet affects overnight and early morning ozone levels. Between midnight and 4 a.m. during the north easterly nocturnal low level jet, hourly

ozone concentrations at Cadillac Mountain are between 70 ppb and 80 ppb. Ozone levelsThe Nature of the Ozone Air Quality Problem in the Northeast: A Conceptual Description Page F-4



### had begun to increase early in the even ing on July 22 and co ntinued to increase throughout the night and peak at 3 a.m. This increasing nighttime ozone at an elevated position corresponds to the nocturnal low leve l jet channeling air up the coast during the night. Conversely, at Cape Elizabeth, a gr ound level site relatively close to Cadillac Mountain, night time ozone levels are much lower than on top of Cadillac Mountain. This difference in ozone at upper and lower levels shows how the nocturnal inversion can

isolate air masses above and below the inversion.

ADI PSE

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Elizabeth 0 20 40 60 80 100 1200:001:002:003:004:005:006:007:008:009:0010:0011:0012:0013:0014:0015:0016:0017:0018:0019:0020:0021:0022:0023:000:001:002:003:004:005:006:007:008:009:0010:0011:0012:0013:0014:0015:0016:0017:0018:0019:0020:0021:0022:0023:00

7/22/2002 7/23/2002Ozone Concentration (ppb)

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7/22/2002 7/23/2002Ozone Concentration (ppb)

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ADI PSE

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Cadillac

Mountain

Cape

Elizabeth Time of LLJ

Figure F-2. Nocturnal low level jet with hourly ozone concentrations at Cadillac Mountain, ME and Cape Elizabeth, ME on July 22 – 23, 2002. Note: Circles in the wind barb plots indicate the location of the nocturnal low level jet.



### The air mass affecting early morning ozon e concentrations in Figure F-2 can be roughly tracked using wind speed and wind direction information from Cadillac Mountain, Pease, Appledore Island, and Ora nge. Assuming the noctu rnal low level jet occurs for five hours that night (based on neighboring wind barb plots), the air mass arriving at Cadillac Mountain at 3 a.m. dur ing peak ozone conditions was over central Massachusetts around 11 p.m. on July 22 when the nocturnal low leve l jet began to form. Tracking this farther back shows that the ai r mass affecting Cadillac Mountain was over western Connecticut around 6 p.m. on July 22. Looking at ozone levels in Cornwall, CT, we see that high ozone conditions existed in this region during the afternoon of July 22 with the average hourly ozone at 112 ppb between 4 p.m. and 7 p.m. Elevated ozone from this region first slowly traveled up the coast in the evening. When the nocturnal low levelThe Nature of the Ozone Air Quality Problem in the Northeast: A Conceptual Description Page F-5



### jet formed, it quickly pushed ozone up the coast affecting ozone levels at Cadillac Mountain, an elevated site in the jet, in the early morning hours (~3 a.m.).

Figure F-3 shows wind profiler information for the next day, July 24, 2002. In this case we see a stronger nocturnal low level je t between midnight and 8am that originates

further to the south. The Fort Meade and Rutgers (RUT) sites show the nocturnal low level jet in the early part of the evening with flow in the northeasterly direction. At higher altitudes slower winds from the west pass over the nocturnal low level jet. Further north, a strong nocturnal low level jet can be seen at Stow, Appledore Island, and Pease. It is difficult to determine if a nocturnal low level jet exists at Orange as high winds continue at the upper altitudes and data are missi ng for the highest al titudes. Figure F-3 demonstrates an example of the nocturnal lo w level jet passing along the east coast as far south as Maryland and as far north as southern Maine.The Nature of the Ozone Air Quality Problem in the Northeast: A Conceptual Description Page F-6

Figure F-3. Nocturnal low level jet on July 23 – 24, 2002. Note: Circles in the wind barb plots indicate the location of the nocturnal low level jet. Data are inconclusive for identifying a nocturnal low level jet at Orange, MA. FME ORE STW ADI PSE

RUT

Direction of

LLJ FME ORE STW ADI PSE

RUT

Direction of

LLJThe Nature of the Ozone Air Quality Problem in the Northeast: A Conceptual Description Page F-7



### Figure F-3 shows that the nocturnal low le vel jet occurred on th e night of July 23- 24 as it did on the previous night. Figure F-4 shows ozone levels overnight on the July 23-24 at Cadillac Mountain and Cape Elizab eth. In this case, we see that low ozone is occurring at both sites dur ing the early hours of July 24. Applying the same methods utilized earlier, wind speed and wind di rection information from Cadillac Mountain indicate that the air arriving at Cadi llac Mountain was also roughly over central Massachusetts at 10 p.m. on July 23 (same wind direction and wind speed as previous day). Wind profiler data show that winds m oved this air mass from eastern New York

and western Connecticut in the late afternoon. Average ozone levels between 4 p.m. and 7 p.m. were 53 ppb at Cornwall, CT. Therefor e, much like on the previous day, air masses were tracked back to the western Connecticut area upwind. In this case, however,

low levels of ozone existed in the air mass.The Nature of the Ozone Air Quality Problem in the Northeast: A Conceptual Description Page F-8

Figure F-4. Nocturnal low level jet with hourly ozone concentrations at Cadillac Mountain, ME and Cape Elizabeth, ME on July 23 – 24, 2002. Note: Circles in the wind barb plots indicate the location of the nocturnal low level jet. Data are inconclusive for identifying a nocturnal low level jet at Orange, MA.



### Examining the wind profiler data from 4 p.m. to midnight on July 23 (Figure F-1 and Figure F-3), we see high winds at a ll altitudes developing throughout the region. Figure F-5 shows that these high winds are part of a weather front that passed through the region in the afternoon of July 23. This corres ponds with the sharp drop in ozone levels at Cornwall, CT, Cadillac Mountain, ME, and Cape Elizabeth, ME (Figure F-6) as the front pushed ozone out of the region. This explains the low levels of ozone seen at Cadillac Mountain during the nocturnal low level jet in the early hours of Ju ly 24. This example demonstrates that not all nocturnal low level je ts are associated with high ozone levels at elevated sites. A necessary condition for the transport of ozone in a nocturnal low level jet is the presence of upwind elevated ozone levels. The front that pushed through the region on the previous day resulted in “clean” air being transported in the nocturnal low level jet. FME ORE STW

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7/23/2002 7/24/2002Ozone Concentration (ppb)

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Elizabeth Time of LLJThe Nature of the Ozone Air Quality Problem in the Northeast: A Conceptual Description Page F-9



### 8AM 7.23.02 8PM 7.23.02

Figure F-5. Weather map displaying a front passing through the East on July 23, 2002.The Nature of the Ozone Air Quality Problem in the Northeast: A Conceptual Description Page F-10

0 20 40 60 80 100 1200:001:002:003:004:005:006:007:008:009:0010:0011:0012:0013:0014:0015:0016:0017:0018:0019:0020:0021:0022:0023:00Ozone Concentration (ppb)

Cornwall CT

Cape Elizabeth, ME

Cadillac Mountain

Figure F-6. Hourly ozone concentrations on July 23, 2002 at three sites.The Nature of the Ozone Air Quality Problem in the Northeast: A Conceptual Description Page G-1



# Appendix G: Contributions to the ozone reservoirThe Nature of the Ozone Air Quality Problem in the Northeast: A Conceptual Description Page G-1



# Appendix G: Contributions to the ozone reservoir

Contributions to the ozone reservoir can co me from two sources. The first is from the residual local ozone and pr ecursors in the atmosphere at sunset. The second is from transport of ozone and precursors from outsi de of the local region. To identify these outside sources, Taubman et al . (2006) have made an analys is of the complete set of aircraft flights undertaken by RAMMPP between 1992 and 2003. Initially, the data were divided into morning and afternoon profiles to identify diurnal patterns. Little diurnal

variation was observed in the carbon monoxide and sulfur dioxide profiles. The ozone values were greater in the afternoon than the morning, while ozone in the lower free troposphere (i.e., above the boundary level), wh ere long range transport is possible, was consistently ~55 ppb. Transport patterns a nd source regions during summertime haze and ozone episodes were analyzed with a cluster analysis of back trajectory data. Eight clusters were identified, which were then divided into morning and afternoon profiles.

Table G-1 lists the characteristics of each cluster, and Figure G-1 shows the back trajectories calculated for each profile divided by cluster at an altitude of 2000 meters. The median profile values were calculated and statistical differences were determined using a nonparametric procedure. When the greatest trajectory density lay over the northern Ohio River Valley, which has large NO X 

### and sulfur dioxide sources, the results were large ozone values, a large SO 2 

### /CO ratio, large scattering particles, and high aerosol optical depth over the mid-Atlantic U.S. In contrast, relatively clea n conditions over the mid-Atlantic occurred when the greatest trajectory density lay over the southern Ohio River Valley and nearly missed many large NO X 

### and SO 2 

### sources. The greatest afternoon ozone values occurred during periods of stagnation that were most conducive to photochemical production. The least polluti on occurred when flow from the northnorthwest was too fast for pollution to accumu late and when flow was from the north,

where there are few urban or industrial sources.The Nature of the Ozone Air Quality Problem in the Northeast: A Conceptual Description Page G-2



### Figure G-1: Maps of the 2 km, 48 hr HY-SPLIT back trajectory clusters for mid-Atlantic region

Note: Cluster groupings are a) cluster 1, b) cluster 2, c) cluster 3, d) cl uster 4, e) cluster 5, f) cluster 6, g) cluster 7, and h) cluster 8. Figure from Taubman et al. , 2006.The Nature of the Ozone Air Quality Problem in the Northeast: A Conceptual Description Page G-3



### Ozone transport over several hundred kilometers into th e mid-Atlantic U.S. was estimated by calculating the ra tio of the residual layer oz one between 500 m and 2 km in the upwind morning profiles to the downwi nd afternoon boundary layer values between 100 m and 2 km. The greatest level of transpor ted ozone (69-82 percent) occurred when the maximum trajectory density lay over th e southern and northern Ohio River Valley (clusters 1, 2, 4, and 6); ~59 percent of the total profiles). The least amount of transported ozone (55-58 percent) was associated with fast southwesterly flow (c luster 8; ~3 percent of the total profiles), fast north-northwesterly flow or clean northe rly flow from regions with relatively few urban or industrial polluti on sources (clusters 5 and 7; ~6 percent of the total profiles), and stagnant conditions wi thin the mid-Atlantic conducive to greater local ozone production (cluster 3; ~27 percen t of the total profiles). The average amount of ozone transported into the Baltimore-Wash ington urban corridor is 64 percent of the

total observed ozone in the afternoon bounda ry layer. If the background ozone is removed, then this value is lowered to 55 percent.

When trajectory density plots were overlaid on maps with the largest annual NO X 

### and SO 2 

### emitters, specific source regions were identified. The results indicate that the areas of maximum trajectory density together with wind speed are effective predictors of regional pollution and loadings. A dditionally, due to the Lagrangi an nature of the dataset, the regionally transported contribution to the total afternoon boundary layer column ozone content in each cluster could be quantified.

Table G-1. Cluster groups for air mass tr ajectories into mid-Atlantic Region

Cluster Description Upwind Region

1 Large ozone values, large SO 2 /CO ratio, large highly scattering particles. Moderate northwesterly flow – aged point source air. Northern Ohio River Valley

2 Small ozone values, large SO 2 /CO ratio. Northwesterly flow at higher wind speeds than Cluster 1 – aged point

source air. Northern Ohio River Valley, extending into the Great Lakes region

3 Large ozone values, small SO 2 /CO ratio. Stagnant conditions with light southerly flow. Central mid-Atlantic region

4 Small ozone values, small SO 2 /CO ratio. Moderate southwesterly flow, small pollution loading – fewer point sources. Southern Ohio River Valley

5 Fairly fast north-northweste rly flow. Flow too fast for pollution to accumulate from source region. Northern Great Lakes

6 Moderately large ozone values, SO 2 /CO ratio very large, smaller less scattering particles. Northwesterly flow, but faster wind speeds than Clusters 1 and 2. Crosses several large SO 2 and NO X sources. Northern Ohio River Valley

7 Least pollution of any of the clusters. Flow is out of the north. Relatively cool, dry continental air. Eastern Ontario, western Quebec

8 Small ozone values, small SO 2 /CO ratio. Fast southwest flow. Very few trajectories. Vicinity of TexasThe Nature of the Ozone Air Quality Problem in the Northeast: A Conceptual Description Page G-4



## Reference

Taubman, B.F., J.C. Hains, A.M. Thompson, L.T. Marufu, B.G. Doddridge, J.W. Stehr, C.A. Peity, and R.R. Dickerson. “Aircraft ve rtical profiles of trace gas and aerosol pollution over the mid-Atlantic United Stat es: Statistics and me teorological cluster analysis.” J

. Geophys

. Res

. 111 , D10S07, doi:10.1029/2005JD006196, 2006.