2002 Progress Report: Investigations of Factors Determining the Occurrence of Ozone and Fine Particles in Northeastern USA

EPA Grant Number: R826373
Title: Investigations of Factors Determining the Occurrence of Ozone and Fine Particles in Northeastern USA
Investigators: Philbrick, C. Russell , Allen, George , Clark, Richard , Daum, Peter , Dickerson, Russell R. , Doddridge, Bruce , Georgopoulos, Panos G. , Hatch, Victoria , Hogrefe, Christian , Kleinman, Larry , Koutrakis, Petros , Lawrence, Joy , Lazaridis, M. , Mohnen, Volker , Munger, J. W. , Porter, Steve , Rao, S. Trivikrama , Ryan, William , Wofsy, Steven C. , Wolfson, Jack M. , Zurbenko, Igor
Institution: Pennsylvania State University , Brookhaven National Laboratory , Harvard University , Millersville University of Pennsylvania , Rutgers, The State University of New Jersey , The State University of New York at Albany , University of Idaho , University of Maryland
EPA Project Officer: Shapiro, Paul
Project Period: April 15, 1998 through April 14, 2003 (Extended to April 14, 2004)
Project Period Covered by this Report: April 15, 2002 through April 14, 2003
Project Amount: $3,000,000
RFA: Special Opportunity in Tropospheric Ozone (1997) RFA Text |  Recipients Lists
Research Category: Air Quality and Air Toxics , Air

Objective:

The objectives of this research project are to: (1) investigate the urban polluted environment to find the relationships and conditions leading to high ozone concentrations and increased levels of fine particles; (2) determine the contributions from local and distant sources; (3) examine the role that meteorological properties play in concentrating and distributing pollutant concentrations; and (4) interpret these results within the context of past measurement programs to extend the knowledge gained to other applicable locations and atmospheric conditions. A major goal of the Northeast Oxidant and Particle Study (NEOPS) project is to develop a useful database for testing and developing the next generation of air pollution models. An additional goal was to test and evaluate new measurement techniques to improve our understanding of the physical and chemical processes which lead to air pollution events. The measurements obtained have focused on obtaining time sequences of data used to study the evolution of air pollution episodes.

Progress Summary:

The latest developments in remote sensing techniques and in situ measuring instruments have been brought together to examine the problems of the urban polluted atmosphere in two intensive 8-week periods during the summers of 1999 and 2001, and during a 3-week pilot study in 1998. Intensive measurements have been made during periods of summer exceedences of the ozone and fine particle concentrations in Philadelphia, PA. Local and distant sources of pollutants have been investigated using an urban site with point sensors and remote sensing instruments, making aircraft measurements to determine the upwind and downwind distribution, and using the network data from other ground sites in the northeast region. The extended summer measurement periods have provided a critical database that describes the vertical and horizontal distribution of the ozone and fine particle concentrations, the local concentrations of chemical species and particulate matter, and the meteorological conditions. These measurements permit investigations to interpret the contributions from local and distant sources to the urban pollution exceedances of ozone and PM10, as well as the new PM2.5 standards. The importance of entrainment and distribution to and from reservoirs in the boundary layer and the lower free troposphere has been investigated.

The project was initiated on April 15, 1998, and the effort to establish a field site began immediately. The field site in northeast Philadelphia was established, and the initial field measurement program was conducted from August 1 to August 22, 1998. The primary objective of the measurement program during the summer of 1998 was to develop the facilities for operation of the field site and to compare several instruments planned for use during the measurements program. In addition, a major air pollution episode of the 1998 summer occurred at the end of the field program, August 21-22, 1998, that provided an excellent data set for air pollution episode investigations. The 1999 field program resulted in a rich data set that included eight periods of intensive study associated with air pollution events, and one of these was the largest event that occurred during the past decade. The 1999 project was extremely successful and a decision was taken to delay the planned 2000 field measurements to 2001, while using the opportunity to upgrade our field site, prepare additional sensors for measurements, provide coordinated measurements with the U.S. Environmental Protection Agency (EPA) Supersite program, and prepare the database for analysis and modeling activity. During the 2001 field measurement program, three interesting periods were identified for special study. Additional efforts in analyzing and reporting the results, and the preparation of the final database archive, are still in progress. Following the field campaigns, the emphasis has been placed on analysis and reporting of the results. We are anticipating approval of our requests for a no-cost extension to prepare the data archive and complete additional analysis of the results.

1998 NEOPS Intensive

The first achievements for the 1998 project were finding the location, preparing the site, and carrying out the first measurement program approximately 3 months after the grant was awarded. This first measurement program permitted the comparison and testing of the many special instruments gathered for the campaign. The measurements obtained during the 1998 intensive clearly show the importance of transported aged materials in the development of significant pollution events. One major episode provided a unique set of vertical profiles from lidar, tethersondes, and aircraft spirals, which show the incursion of processed precursor materials from an aloft layer, transported into the region, and then mixed downward to the surface by the rising daytime convective boundary layer. The initiation of an ozone and particulate matter event on August 21, 1998, was captured in vertical profiles of the ozone, aerosol extinction, water vapor, and other meteorological parameters. Time sequences of ozone and aerosol particulate matter profiles obtained during the NEOPS project pilot study show the importance of the surface layer dynamics in determining the surface concentrations. Several times during the 2-week period of the pilot study, hazardous levels of ozone were observed to exist above the surface layer. Vertical mixing determines the transport between the tropospheric transport reservoirs and surface layer gases. Ozone was observed to remain in nighttime reservoirs at altitudes above the planetary boundary layer, where long distance transport becomes important in determining the local concentration. The variations in vertical transport can increase the exposure of the surface dwelling population.

The NARSTO-NEOPS research carried out by the consortium of investigators from universities and government laboratories participating in the pilot study in August 1998, are listed in Table 1. The primary purpose of the 1998 study was to establish the site and compare instrument platforms as preparation for future intensive measurement campaigns. However, the August 21-22, 1998 measurement period included a significant pollution episode, when substantial increases in both ozone (concentration 125 ppb) and airborne particulate matter (PM2.5 65 µg/m3) were observed. Results from that episode, which show the lidar time sequences of ozone and water vapor, are presented in Figure 1. The water vapor profile provides a useful tracer for describing the variations in boundary layer dynamics. This unique set of vertical profiles obtained with lidar, tethersondes, and aircraft spirals clearly show the incursion of aloft precursor materials, which were transported into the region, and mixed downward to the surface by the rising daytime convective boundary layer. The transported material appears to be responsible for the initiation of an ozone and particulate matter pollution event on August 21, 1998. Vertical profiles of the ozone, aerosol extinction, water vapor, and other meteorological parameters were obtained almost continuously over a 3-day period, and these time sequence profiles clearly show the upper layer transport and mixing. This first depiction of the meteorological control of a pollution event provides a valuable case study and indicates the type of results expected from the intensive measurement periods planned during the next two sets of intensive summer measurements.

The 1998 program was intended to prepare the field site and to evaluate the instrument techniques. Techniques used during the investigation included a wide range of instruments that measured the surface layer and boundary layer properties. The NEOPS measurements in Philadelphia provide a central location and the important regional measurements of the meteorological properties using remote sensing and aircraft measurements. The primary purposes for performing the 1998 pilot study were to prepare the measurement site in Philadelphia that would be used for measurements during the next 3 years and to gather data to investigate the comparisons of the instrument techniques. During the pilot study, the most significant pollution episode of the 1998 summer occurred on August 21-22. The NARSTO-NEOPS program is intended to add to our understanding of the relative importance of the various physical and chemical processes which control the evolution and development through dissipation during air pollution episodes. The data from this program will be used to test the capability of the next-generation air quality models to provide short-term (1-2 day) predictions of the concentration levels of air pollution hazards over regional scales. Future needs for regulatory actions cannot be undertaken without major improvements in our detailed understanding of the processes controlling the evolution of air pollution events and a demonstrated capability to accurately model the air quality hazards over the region.

Figure 2 shows a comparison of the lidar, tethersonde, and aircraft profiles of water vapor during a period of afternoon convection. The water vapor profiles are particularly important in providing a tracer for boundary layer dynamics. The boundary layer thickness determines the mixing volume for dilution of air pollution and is important for evaluation of the meteorological models used to describe air pollution episodes. The University of Maryland used a Cessna aircraft to obtain profiles and distributions of ozone, water vapor, and temperature during 12 flights as part of the August 1998 campaign. The Millersville University tethersonde instrument is able to provide high resolution profiles from the surface to 300 meters every 30 minutes using a 4-m long (5 m3) tethered balloon. During the summer of 1998, 176 vertical profiles were obtained. The instrument package profiles the temperature, pressure, wind velocity, relative humidity, and ozone. A larger 12-m long (100 m3) balloon was tethered at 300 meters and carried Personal Environmental Monitors (PEMs) suspended at 75, 150, 225, and 300 meters for 10-hour periods (10 a.m. to 8 p.m., and 10 p.m. to 8 a.m. local time) and the filters were analyzed by Harvard School of Public Health (HSPH). A more detailed meteorological description for the events has been prepared by Dr. William Ryan. The University of Maryland used a Cessna aircraft to obtain profiles and distributions of ozone, water vapor, and temperature during 12 flights as part of the August 1998 campaign. Figure 2 shows an example of the comparisons of the lidar, tethersonde, and aircraft profiles. Generally good agreement between the sensors has been found and detailed comparisons will be presented in reports that are in preparation. Figure 3 shows an example of the comparisons of the lidar and aircraft ozone profiles. Generally good agreement sensors have been found, and differences have shown where improvements in sensors are needed.

1999 NEOPS Intensive

Advanced techniques used during the NARSTO-NEOPS project included Raman lidar, tethersonde balloons, particle/chemical samples using HSPH instruments (TEOMS, HEADS, and HVTOX), and the latest aircraft sampling techniques on the DOE-G1 and UMD aircraft. The Raman lidar has proven to be a useful tool for providing time sequences of vertical profiles of ozone, temperature, water vapor, and optical extinction. Profiles of the properties of the surface layer to 300 meters were obtained by Millersville University using tethersondes for ozone, temperature, water vapor, wind velocity, and fine particle concentration. The regional distributions of particulate matter, chemical species, and meteorology were obtained using the University of Maryland instrumented aircraft for 24 flights and the DOE-G1 instrumented aircraft for 19 flights. The latest techniques for measuring the particulate matter properties were used by HSPH, Drexel University, and Brigham Young University (BYU). The contributions of the researchers participating in the project are shown in Table 2.

Instrument setup for the summer intensive at the Baxter Water Treatment Plant began on June 15, 1999, and the site was fully operational from June 28 to August 19, 1999. Particulate matter and gaseous samplers were continuously operated during the project by HSPH and NOx/NOy chemistry by Harvard University. Profiles of ozone, meteorological parameters, and optical extinction were obtained each day with PSU lidar, except for the period from July 18-21. Measurements were made by Millersville University using the two tether balloons during intensive periods and other interesting periods. The smaller tether balloon (5 kg capacity) measured profiles of meteorological properties and ozone from surface to 300 meters and obtained a total of 430 profiles. A larger tether balloon (50 kg capacity) was used to suspend PM2.5 filter samplers, continuous optical scattering instrument for PM2.5, and VOC canisters at several altitudes between the surface and 300 meters. The NEOPS Radar/RASS sounder, obtained from EPRI with support from Mid-Atlantic Regional Air Management Association (MARAMA) and PECO, was placed into operation at the Philadelphia site on July 23 and operated through the program. Dynamical properties of the meteorological fields are investigated using the data from this Radar/RASS and two other sounders from the Argonne National Laboratory (ANL) and the Pacific Northwest National Laboratory (PNNL). Particulate matter samples were collected each day by Drexel University for gas chromatography/mass spectrometry (GC/MS) analysis of minor species. The University of Maryland provided CO and UV radiation measurements at the site and conducted instrumented flights with Cessna and Aztec aircrafts. Brookhaven National Laboratory made 19 regional flights using the instrumented DOE-G1 aircraft between July 25 and August 11. PNNL released 61 radiosonde balloons and 10 ozonesonde balloons between July 23 and August 10 from the Philadelphia site. PNNL set up and operated a Radar/RASS sounder at West Chester, PA (about 30 miles west) from July 23 to August 11. ANL operated a mobile chemistry laboratory and a Radar/SODAR sounder at Centerton, NJ (about 30 miles south) during the period July 24 to August 11. At the Centerton site, ANL released 56 radiosonde balloons. During the period July 2-30, BYU used three instruments to measure the volatile and semi-volatile mass and species of particles.

As part of the 1999 NARSTO-NEOPS field campaign, the DOE G-1 aircraft conducted 19 research flights in and around Philadelphia. Most flights consisted of boxes around the Philadelphia urban area. The northeast side of the smallest box was located about 20 km from downtown Philadelphia and included vertical spirals and horizontal transects providing detailed coverage between 300 meters and 2.5 to 3 km. Repeated transects at different times of the day gave information on vertical mixing. Trace gas measurements pertinent to understanding O3 formation included O3, CO, VOCs, NO, NOy, SO2, HCHO, H2O2, and organic peroxides. Measurements of these species were input to a constrained steady state box model that gave predictions for radical concentrations and the rate of O3 production. Highest O3 concentrations in the program were observed on July 31, a day with very light wind speeds.

Figure 1. Time Sequence of Ozone and Water Vapor Mixing Ratio. Raman lidar profiles show the growth of the PBL during the morning of August 21. Using the water vapor as a tracer, the rising PBL brings transported species to the surface, which appears to initiate the ozone and PM event.

Figure 2. Water Vapor Profiles. Water vapor profiles, which provide a good tracer for boundary layer dynamics, were obtained using lidar, tethersonde, and aircraft.

Table 1. Measurements Obtained in August 1998 NARSTO-NEOPS Campaign

Penn State University - Russell Philbrick
     Raman Lidar - Profiles of specific humidity, temperature, ozone, optical extinction (285, 530, and 607 nm)

Millersville University - Richard Clark
     Tethered Balloon - 100 m3 – 10-hour aloft with sensors at surface, 100 m, 200 m, and 300 m AGL
     (1) PEMS 4 each - 4 L/min dry PM 10-hour integrated sample
     (2) Diode Laser Scatterometer (DustTraks) 1.7 L/min continuous data
     Tethered Balloon - 7 m3 - up/down scan to 300 m each hour
     T, rho, RH, wind speed, and direction 1-m vertical resolution and O3 by KI method
     Surface Measurements - O3 and meteorological data
     Meteorological Data Archive - radar, satellite images, surface observations, upper air data, ETA/RUC model

Harvard School of Public Health - Petros Koutrakis and George Allen
     Mass density of particulates: PM1, PM2.5, PM10, aerosol-size, EC/OC, sulfate, nitrate, toxics

Harvard University - Bill Munger
     NOy concentrations and fluxes are used to infer the rates for NOx oxidation and deposition

University of Maryland - Bruce Doddridge and Bill Ryan
     Instrumented aircraft Cessna 170: global positioning system, ozone, carbon monoxide, and a temperature/relative humidity probe
     Ozone and PM event forecasting, description of evolution of interesting episodes, and meteorological modeling

Drexel University - Steve McDow
     (1) Organics in PM2.5 with GCMS analysis: non-polar components (alkanes, PAH), acids, and diacids
     (2) Polar Organics for GCMS with derivatization using PM10 with composite samples


Figure 3. Ozone Profile. The aircraft and lidar profiles of ozone are compared during a spiral by the aircraft near the vertical beam of the lidar. The ±1s error associated with the photon counting is indicated on lidar data.

A mid-morning and mid-afternoon flight indicated that the O3 increase observed from the G-1 (from about 90 to 130 ppb) can be accounted for by local production. On the same day, an industrial plume with extreme values of NO, CO, VOCs, and SO2 was traversed to southwest Philadelphia. This plume was found at the same location in the afternoon with lower concentrations of primary pollutants and with a peak O3 of 143 ppb.

Figure 4 shows the results from a calculation of ozone production efficiency. Data are from the G-1 aircraft on 3 days with highest O3 observed during field campaigns in Houston (2000), Philadelphia (1999), and Phoenix (1998). The slopes in this graph show the number of O3 molecules formed per molecule of NOx that is used up (converted to oxidation products—denoted as NOz). In these three cities, 20-30 ppb of NOx was used in forming O3. Maximum O3 levels differ because the efficiency of O3 production varies from city to city. Our calculations indicate that differences in O3 production efficiency are largely because of the differences in VOC reactivity. Efficiencies are much higher in Houston because of reactive VOCs from
petrochemical facilities.

Figure 4. DOE G-1 Aircraft Data From High Ozone Days Used to Calculate Ozone Production Efficiency in Three Cities

2001 NEOPS Intensive

The summer of 2001 was the time that brought together the largest capability to investigate the particulate matter associated with air pollution investigations (see Table 3). The third summer intensive originally had been planned to take place in 2000, but it was decided to delay it until 2001 because of the opportunity to bring a special focus for the three Supersite activities planned for July 2001. The EPA Supersites established in New York, Pittsburgh, and Baltimore had planned to operate during July 2001 and none of these efforts included the type of investigations that have been carried out in NARSTO-NEOPS. Because our Philadelphia NEOPS site is centrally located relative to these sites, it appeared logical to move our measurement program to coincide with the Supersite activity. We were quite successful in gathering the data planned for the NEOPS site and expect that we will be able to provide the regional context for the air pollution during the campaign. The NEOPS data includes vertical sounding for the meteorological and air quality soundings and a few periods when aircraft measurements extend the regional description. The modeling 9-10 and regional forecasting description that the NEOPS investigators (see Table 4) have provided should be extremely valuable for the analysis and interpretation of the Supersite results.

Table 2. List of Measurements Obtained During the June-August 1999 NARSTO-NEOPS Campaign

Penn State University - Russell Philbrick
     Raman Lidar - Profiles of specific humidity, temperature, ozone, optical extinction (285, 530, and 607 nm)
     Radar-RASS - Wind velocity, virtual temperature
     10 m Tower - Temperature, dew point, relative humidity, wind velocity, wind gust, solar flux, atmospheric pressure, precipitation

Millersville University - Richard Clark
     Tethered Balloon - 100 m3 - 10 aloft with sensors at surface, 100 m, 200 m, and 300 m AGL
     (1) Personal Environmental Monitors (PEMS) 4 each - 4 L/min dry PM 10-hour integrated sample
     (2) Diode Laser Scatterometer (DustTraks) 1.7 L/min continuous data
     (3) VOC - Micro-orifice vacuum canister at surface and at 300 meters, 10-hour accumulated sample with GC/MS laboratory analysis
     Tethered Balloon - 7 m3 - up/down scan to 300 m each hour
     (1) Meteorological properties: T, rho, RH, wind speed and direction and 1-m vertical resolution
     (2) O3 by KI oxidation method, 2-3 second time resolution (1-m altitude)
     Surface Measurements - O3 and meteorological data
     Meteorological Data Archive - radar, satellite images, surface observations, upper air data, ETA/RUC model output

Harvard School of Public Health - Petros Koutrakis and George Allen
     Mass density of particulates: PM1, PM2.5, PM10, aerosol-size, EC/OC, sulfate, nitrate, toxics

Harvard University - Bill Munger
     NOy concentrations and fluxes are used to infer the rates for NOx oxidation and deposition

University of Maryland - Bruce Doddridge and Bill Ryan
     (1) Instrumented Aircraft Cessna 170 and Aztec: global positioning system, ozone, carbon monoxide, and a temperature/relative humidity probe
     (2) Ozone and PM event forecasting, description of evolution of interesting episodes, and meteorological modeling

Drexel University - Steve McDow
     (1) Organics in PM2.5 with GCMS analysis: non-polar components (alkanes, PAH), acids and diacids using Hi-Vol 24-hour sample
     (2) Polar Organics for GC/MS with derivatization using PM10 with composite samples

Brookhaven National Laboratory - Peter Daum, Larry Kleinman, Yin-Nan Lee, Stephen Springston
     DOE G-1 Instrumented Aircraft - particulate and gas-phase chemistry

Brigham Young University - D. Eatough
     Measurement of particle volatile mass component and identification of volatile species with RAMS and PCBOSS

Pacific Northwest National Laboratory - C. Doren, J. Allwine, J. Fast, C. Berkowitz
     Radiosondes - Pressure, temperature, humidity 0-15 km at Philadelphia, Radar-RASS instrument at West Chester, 12 ozonesondes at Philadelphia

Argonne National Laboratory - R. Coulter, J. Gaffney, N.A. Marley
     Radiosondes, SODAR, and chemistry laboratory at Centerton, NJ

North Carolina A&T State University - D. Dunn
     Remote sensing with lidar and SODAR

North Carolina State University - H. Hallen
     Laser remote sensing, particle optical scattering properties


Table 3. List of Measurements Obtained During the July 2001 NARSTO-NEOPS Campaign

Penn State University - Electrical Engineering - Russell Philbrick
     (1) Raman Lidar - Profiles of specific humidity, temperature, ozone, optical extinction (285, 530, and 607 nm)
     (2) Radar-RASS - Wind velocity, Virtual Temperature
     (3) 10-m Tower - Temperature, dew point, relative humidity, wind velocity, wind gust, solar flux, atmospheric pressure, precipitation
     (4) Radiosondes - Pressure, temperature, humidity 0-15 km

Penn State University - Meteorology - Bill Ryan and Nelson Seaman
     Ozone and PM event forecasting (with University of Maryland), description of evolution of interesting episodes and meteorological modeling

Millersville University - Richard Clark
     Tethered Balloon - 100 m3 - 10 hours aloft with sensors at surface, 100 m, 200 m, and 300 m AGL
     (1) Personal Environmental Monitors (PEMS) 4 each - 4 L/min dry PM 10-hour integrated sample
     (2) Diode Laser Scatterometer (DustTraks) 1.7 L/min continuous data
     (3) VOC - Micro-orifice vacuum canister at surface and at 300 meters, 10-hour accumulated sample with GC/MS laboratory analysis
     Tethered Balloon - 7 m3 - up/down scan to 300 m each hour
     (1) Meteorological properties: T, rho, RH, wind speed and direction 1 m vertical resolution
     (2) O3 by KI oxidation method, 2-3 second time resolution (1 meter altitude)
     Surface gas and particles - O3, NO/NO2/NOx, SO2, CO, 3-lambda Nephelometer
     Meteorological Data Archive - radar, satellite images, surface observations, upper air data, ETA/RUC model output

Harvard School of Public Health - Petros Koutrakis and George Allen
     Particle size and count: 0.02 to 0.6 µm electrostatic classification, 0.7 to 15 µm time of flight, PM2.5 CAMM, black carbon soot aethalometer,
          sulfate from HSPH thermal conversion method, EC/OC analyzer
     Particulate 10-hour Day/Night Samples: HEADS for acid gases (HNO3, HONO, SO2), NH3, and sulfate/nitrate/strong aerosol acidity
          EC/OC on quartz filters with DRI's TOR analysis, PM2.5 and PM10 from Harvard impactors with Teflon filters and gravimetric analysis
          daily, Hivolume OC speciation sampler, HSPH PUF substrate collection; Drexel University selected filter analysis

Harvard University - College of Engineering - Bill Munger
     NOy concentrations and fluxes are used to infer the rates for NOx oxidation and deposition

University of Maryland - Bruce Doddridge and Russ Dickerson
     Instrumented Aircraft Piper Aztec: particle-soot absorption photometer, global positioning system, ozone, sulfur dioxide, carbon monoxide,
          3-wavelength integrating nephelometer and a temperature/relative humidity probe
     AERONET (Aerosol Robotic Network) data available include AOT at 1020, 870, 670, 500, 440, 380, and 340 nm plus precipitable water (cm)

Drexel University - Steve McDow
     (1) Organics in PM2.5 with GCMS analysis: nonpolar components (alkanes, PAH), acids, and diacids using Hi-Vol 24-hour sample
     (2) Polar organics for GCMS with derivatization using PM10 with composite weekly samples
     (3) Metals with inductively coupled plasma mass spectrometer (ICPMS) low volume teflon membrane filter daily 24-hour sample

Clarkson University - Phil Hopke and Alex Polissar
     (1) PM2.5 with 0.5-hour resolution using RAMS, TEOM, and 3OC
     (2) PM2.5 with 1-hour resolution using CAMM's instrument
     (3) Nephelometers - with and without dryer

EPA - RTP and Texas Tech University - Bill McClenny (EPA) and Sandy Dasgupta (Texas Tech)
     (1) Fluorescence Detector: H2O2, HCHO, MHP, NH3
     (2) Ion Chromatography: sulfur dioxide, nitric acid, nitrous acid, HCl, oxalic acid, oxalate, nitrate, nitrite, sulfate, chloride, ammonium

Brookhaven National Laboratory - Larry Kleinman, Linda Nunnermacker, Xiao-Ying Yu, Yin-Nan Lee, Stephen Springston
     IC data on cations: Na+, K+, NH4+, Ca2+ and anions: SO42-, NO3-, Cl-, NO2-, oxalate; 3-channel NOx, CO, ozone, SO2

Carnegie Mellon University - Spyros Pandis
     Particulate Matter 0.02 to 0.6 µm, electrostatic classification, run dry

Philadelphia Air Management Services - Fred Hauptman and Lori Condon
     Speciation Air Sampling System: PM2.5 mass, trace metals, organic and elemental carbon, sulfate, nitrate, and other ions/elements


Table 4. Modeling Activities Included as Part of the NARSTO-NEOPS Program

State University of New York at Albany - S.T. Rao, V. Mohnen, I. Zurbenko, S. Porter, K. Civerolo
Regional analysis and model calculations of polluted air masses

Rutgers University, Environmental and Occupational Health - P. Georgopoulos and M. Lazaridis
Emissions inventories and chemistry modeling, particular experience in Philadelphia area


Progress April 15, 2002 to April 15, 2003

General scientific work that makes use of the program results has been carried on during the year. Meanwhile, we have been waiting for a no-cost extension of the project that would permit the expenditure of the small amount of remaining funds for preparation of the data archive and for support of publications. The extension covering this period was received June 24, 2003, and a request for a further extension has been made to allow this effort to begin.

Summary of Measurement Intensive Results

The NARSTO-NEOPS project has included three major measurement programs. The participants and measurements conducted during the campaigns in the summers of 1998, 1999, and 2001 have been summarized in Tables 1, 2, and 3. Significant measurement periods that have been selected for specific investigations are summarized in Table 5. The 1998 program was intended to prepare the field site and to evaluate the instrument techniques. During the summer of 1999, the first intensive measurements were carried out over a 2-month period that captured data during eight periods of significant air pollution episodes, including one which recorded the highest O3 in Philadelphia during the past decade. Techniques that were used during the investigation included a wide range of instruments that measured the surface layer and boundary layer properties. The summer 2001 campaign was conducted during a period that did not contain any major air pollution events; however, three interesting periods have been identified. The plan to delay the NEOPS measurements from summer 2000 to summer 2001 was an effort to provide an important coordination role in relating the measurements of the three northeastern Supersites in New York, Pittsburgh, and Baltimore. The NEOPS measurements in Philadelphia provide a central location and the important regional measurements of the meteorological properties using remote sensing and aircraft measurements. The results obtained during the field measurements provide a unique opportunity to investigate many topics of interest in the community. The list of topics in Table 6 summarizes some of the scientific investigations, which either are completed or planned by the several research groups using the NEOPS results.

It is interesting that so many other universities and laboratories joined in with the field measurements program after the field site was established. Year 2 of the project resulted in the participation of four university groups and two government laboratories, in addition to those that were supported by the EPA consortium. These additional six groups were afforded the opportunities of the established site, including power, communications, shelter space, etc., and they significantly contributed to the overall successes and results of the program. During the 2001 campaign, four other universities and two additional laboratories joined the effort.

Table 5. Summary of the Intensive Observational Periods During 1998, 1999, and 2001 Campaigns

  Summer 98 August 7-22, 1998
1 7-22 Aug Pilot study to prepare site and evaluate instruments
2 21-22 Aug Sudden ozone and PM event with vertical mixing of transported material
  Summer 99 July 28–August 20, 1999
1 3-5 July Ozone event limited by strong winds, depth of PBL, variation in local emissions due to traffic change, UMD A/C
2 8-10 July Weak cold front oscillation north/south, frontal passage effects, ozone and PM enhanced in PBL as front approached
3 16-21 July Major ozone event, UMD aircraft
4 23-24 July Limited regional ozone, very strong stable PBL, wind shift, RASS, and sondes
5 27 July-1 Aug West flow brings increase in ozone on 27th, regional convection limits ozone on 28th, 31st has high ozone, DOE-G1 and UMD aircraft, ozone 162 ppb surface-180 ppb aloft
6 7-8 Aug Particulate matter event
7 11-13 Aug Recirculation event, 125 ppb on 12th followed by storm on night of 13th
8 15-17 Aug Standard ozone event but did not last to produce large build up of ozone, UMD Aztec
  Summer 01 June 29–August 1, 2001
1 10 July Sudden event that is short duration, begins with interesting convective activity
2 16-17 July Ozone and PM event
3 20-25 July Moderate levels of ozone repeated on succession of 4 days

Table 6. Science Investigation Topics Developed Using NEOPS Data


1. Change in particle size with changes in air mass.
2. Sea-breeze events and bay effects on airborne particulate matter and ozone.
3. Limiting rates of ozone photochemistry production/destruction compared with observations.
4. PBL dynamics influencing the evolution of pollution events.
5. Comparison of Philadelphia and Fort Meade PM during July.
6. Relative amounts of semi-volatile PM in anthropogenic (Philadelphia) versus biogenic (Atlanta) aerosol.
7. Relative contributions of stratospheric ozone to tropospheric ozone during pollution events.
8. Nocturnal low level jet - vertical shear.
9. Thickness of daytime PBL as variation in volume for distribution of ozone and PM; different over NJ and over Philadelphia (heat island effect).
10. Model developments for, and testing with, NEOPS data–SUNY-Albany, PNNL, PSU, UMD, EPA Region 3, EPA-RTP, Carnegie-Mellon–improve our understanding of the boundary-layer evolution processes and their influence on ambient concentrations of ozone and fine particles in the Northeast.
11. Identify the synoptic and meso-scale meteorological conditions conducive to the accumulation of ozone and fine particles in the Northeast.
12. Identify space and time scales relevant to regulatory policies on ozone and fine particle pollution in the Northeast.
13. Provide high-resolution data for evaluation and further development of new generation air quality modeling systems such as Models-3.
14. Develop advanced methods for measuring the vertical distribution of ozone and fine particles on a continuous basis and validate the time resolved data against integrated methods.
15. Develop a comprehensive database of speciated fine particulate matter to help identify potential source-receptor relationships for ozone and fine particle pollution in the Philadelphia area.
16. Determine the role of vertical mixing in establishing the surface ozone and PM concentrations that contribute to human exposure levels.
17. Describe the role of the nighttime reservoir region in storing and transporting polluted air masses that contribute to surface concentrations on the following day.
18. Integrated and continuous measurements of PM2.5 and its key chemical components are made to provide the “endpoint” of the atmospheric chemistry and meteorological processes that drive the short- and medium-term temporal variation of ambient pollutants that are of concern in health effects exposure assessment research.
19. The integrated measurement methods establish a basis for interpretation of continuous methods, as well as provide speciation information that is not continuously measured; the continuous methods provide high-resolution temporal information (1 hour or less) that is not available from the integrated methods (10- to 24-hour duration). Together, the two classes of measurement techniques compliment each other to provide a more complete description of the composition and temporal variability of ground-level PM.
20. Cross-corridor correlations using aircraft and remote sensing.
21. Correlation of PM and ozone.
22. Ultrafine particle variations and correlation with haze events, ozone, and PM.
23. Downward mixing from residual boundary layer.
24. Evolution of PBL.
25. Distant transport of pollutants and precursors.
26. Influence of local input of plumes from tall stacks.
27. What is the contribution of stratospheric ozone to the troposphere, magnitude of variation.
28. Dynamical description of the region during pollution events.
29. Ozone response and distribution variations caused by NOx and VOCs.
30. Examine corroborations of emissions inventory with ambient data.

Key Findings From the NARSTO-NEOPS Program

Twelve Episodes for Model Development and Testing. Twelve major air pollution episodes were measured during three summers that provide data on a wide range of atmospheric variations. The results from the NEOPS program can be used to develop and verify performance of future models intended to describe air quality.

Vertical Profiles Necessary. The vertical profile measurements from lidar, radar, acoustic sounding, balloons, and aircraft of the NEOPS program have demonstrated that vertical profiles are required to understand any air pollution episode. The measurements show that it is not possible to describe the development and evolution of air pollution events with ground-based measurements alone. An integrated approach (surface, aircraft, balloon, and lidar) seems capable of discerning changes in PBL dynamics—most importantly PBL height and diurnal development—on time and space scales consistent with the urban corridor.

Unique Data Set With Vertical Profiles. The NEOPS program has provided a unique data set to examine the vertical distribution of air pollutants, ozone and particulate matter, and the vertical profiles of the meteorological properties. There are no other projects that have developed the detailed picture of the distribution of the important properties and evolution of air pollution episodes. Results comparing in situ aircraft data, tethered balloon data, and remote sensing with lidar and radar data show consistency between independent upper-air data sets for temperature, water vapor, and ozone.

Remote Sensing Importance. The Raman lidar and Radar/RASS instruments have provided a core set of data, which provides an opportunity to analyze the detail processes controlling the development and dissolution of air pollution events.

Storage and Transport Aloft. High levels of ozone are frequently found to travel in layers above the surface and go undetected by the ground-based sensors. It is only during periods of strong afternoon convection that the ozone levels distributed through the lower troposphere are actually observed at the ground. The layering processes also result in the transport and distribution of precursor materials overhead that are mixed to the ground and contribute to the photochemical production.

Regional Transport. The major air pollution episodes observed in Philadelphia are meteorologically controlled and associated with transport of pollutants and/or precursors from the continental regions of the Midwest. Because ozone can be transported several hundred kilometers downwind of its source region during its lifetime, depending on upper-level winds, effective ozone control strategies need to take into consideration the spatial scales ranging from local to regional, and time scales of the order of several days.

Rapid Growth of the Daytime Mixed Layer After Sunrise. The rapid growth of the mixed layer allows significant quantities of ozone, precursors, and particulates to be mixed down to the surface, causing rapid increases in their respective concentrations in times that are short compared to the photochemical formation of ozone or the local production of PM.

Sea Breeze Influence. The sea breeze convergence zones' influence on the air chemistry in Philadelphia causes the ozone concentration to decreased rapidly, often by a factor of two, while PM concentrations increase because of the deliquescence of sub-micron aerosols to sizes detectable by the laser-diode scatterometers in the moist, maritime air mass. Sea breeze fronts typically are fumigation events that must be adequately modeled and factored into the evolution of the regional air mass if accurate prediction of an ozone event is to be realized.

Nocturnal Low-Level Jets Transport. Nocturnal low-level jets (LLJ) are known to transport significant quantities of precursors, pollutants, and particulates great distances, and contribute to increases in trace gas and particulate concentrations in areas where the local production may not have yielded exceedances. Delineation of the vertical structure based on the NEOPS field experiment shows that the LLJ forms under clear sky conditions in the presence of a quasi-stationary high pressure system, which allows for a maximal amount of differential heating and cooling along the northeast corridor. Other findings associated with LLJ phenomena are the "bursting" events that occur in the early morning hours that result from mechanical (dynamical) instabilities in the shear zones below the layer of maximum winds. These bursting events vertically mix ozone to the surface even in the presence of thermodynamic stability causing increases in ozone concentrations of 20-30 ppbv in the absence of local production and solar insolation. LLJs were found to be present during the night when large ozone exceedances occurred during the day. The RAMS4.3 predictions successfully simulated the nocturnal low level jets observed during the period July 16-19, 1999.

Air Chemistry in Philadelphia.
• Strong correlation at all hours between PM2.5 and sulfate (r=0.94).
• On average, sulfate-related mass (assuming ammonium sulfate) accounted for 55 percent of the PM2.5.
• For hours with PM2.5 > 60 µg/m3, the mean of sulfate was 71 percent.
• Daily maximum (1-hour) values show the relationship between PM2.5 and ozone; r = 0.58.
• Daily mean values show correlation; PM2.5 and ozone (r = 0.77), and sulfate and SO2 (r = 0.62).
• Fresh vehicle emissions have a NOx:CO ratio of 0.18 mol/mol during the summer.
• The mixture of regional background air and local emissions exhibits a 33 percent removal of nitrogen oxides during mid-afternoon on average.
• The highest ozone events were the most depleted in NOy.
• Background levels of ozone associated with the cleanest air at Philadelphia were 47 ppb.

Representativeness of Results. The NEOPS primary surface site seems under most conditions, certainly during the afternoon within a convective boundary layer, representative of the PBL over a major Northeast U.S. urban/industrialized corridor.

Aircraft Delinate Regional Characteristics. Aircraft data show substantial differences in air quality (ozone, haze, and precursors) across the PHL urban corridor in the vertical, with substantial afternoon ozone/haze formation observed often downwind of the corridor. The comparisons of both CMAQ and MAQSIP model predictions with surface measurement data from AIRS and NEOPS show reasonable agreement for O3. The model predictions capture the general trends of change in the time-series plots. The comparison with NEOPS aircraft data demonstrates the general ability of both models to simulate major aspects of the vertical structure of pollutant distributions.

Value of Satellite Data Recognized. Satellite data were found to provide additional insight into the regional picture of air pollution and haze events. Satellite data confirm aircraft observations that even the lower atmospheric column often is decoupled from the surface layer with respect to air quality (ozone and fine particle haze).

Major Influence From Regional Scales. Back trajectory analysis and modeling show importance of transport of primary pollutants and precursor materials. Ozone and fine particulate matter are found to have the potential to affect regions over spatial scales on the order of 600 km in the Northeastern United States.

Meteorology and Visibility Factors Control. Results from a 3-month simulation of the meteorological conditions over the Northeastern United States with the MM5 mesoscale model, combined with analyses of surface ozone observations and NEOPS data, demonstrate the control meteorology and solar illumination in the evolution of air pollution events.

Model Parameters Need Data to Constrain and Test. The choice of boundary layer parameterization in the meteorological model has a significant impact on the magnitude and location of daily maximum ozone concentrations predicted by the photochemical model. In addition, the photochemical model’s response to changes in the emissions inventory reveals that the choice of equally valid boundary-layer parameterizations can significantly influence the efficacy of emission reduction strategies. Results indicate that the MM5 application with 14 layers in the vertical direction was able to capture the atmospheric mesoscale structure in a manner comparable to the application employing 21 layers in the vertical direction. The results of the RAMS/LES study suggest that the explicitly resolved energetic eddies seem to provide the correct forcing necessary to produce good agreement with observations for the case of lower imposed sensible heat flux at the surface. Overall, the meteorological and air quality models considered are showing success in simulating the observed mesoscale structure of the atmosphere and general characteristics for ambient air quality.

Inter-City Comparisons. The statistics on O3 concentration and production rate for five cities have connected the urban scale photochemical oxidant field campaigns. Of the five cities studied, Houston has the worst O3 air quality problem, because of the reactive olefins from petrochemical facilities causing VOC reactivity, O3 production rate, and O3 production efficiency (molecules of O3 formed per molecule of NOx) to be significantly higher in Houston than elsewhere. Philadelphia, of the other four cities, is the best standard of comparison. In many chemical ways, Philadelphia resembles Houston, but without a dominant petrochemical industry. One lesson that we have learned from Houston is that emission inventories prepared in strict adherence to EPA's guidelines can contain order of magnitude underestimates of industrial VOC emissions.

Key Conclusions of the NARSTO-NEOPS Program

(1) Meteorology is the primary driver and leading factor controlling high ozone and particulate matter episodes in the Northeast. Under conditions of quasi-stationary anticyclonic conditions, pollutants can build to levels that could have a deleterious effect on the health of the population. Levels tend to significantly rise with the approach of a short wave trough or frontal boundary, but then precipitously fall with the passage of the wave or front. It is paramount that numerical mesoscale models are fit with improved parameterizations that better characterize sub-grid-scale phenomena if the dynamics and timing of mesoscale phenomena are to be adequately simulated.

(2) Local and regional scale circulations can have a dramatic influence on the modifications to the boundary layer and the attendant concentrations of trace gases and particulate matter. The Northeast corridor is an area where complex interactions between the synoptic, meso- and micro-scales of atmospheric circulations occur. Superimposed on a propagating synoptic air mass are urban plumes embedded in developing, evolving boundary layers advected by the mean wind, buoyancy and mechanical instabilities regimes, low-level nocturnal wind maxima, gravity waves, deep convection within squall lines which create outflow boundaries, migrations of the Appalachian leeside trough, deep convection, sea and bay breeze convergence zones, and frontal recirculations.

(3) The modeling analyses performed in this study showed that, overall, the meteorological and air quality models considered (MM5, RAMS, Models-3/CMAQ, MAQSIP) generally were successful in simulating the observed mesoscale structure of the atmosphere and ambient air quality. This increases the confidence in the use of these models by state and federal regulatory agencies for emission control strategy development and evaluation. In particular, the successful application of simpler modeling options, as mentioned in the key findings, based on the cross-evaluation with models employing more comprehensive options, and the NEOPS ground and upper air data, provides substantial confidence for adoption of these simpler options. This is very important as it will allow the longer-term (i.e., seasonal or annual) application of these models in relation to important regulatory issues.

Implications of the Results From NARSTO-NEOPS

(1) Rapid removal of NOy complicates the interpretation of O3:(NOy-NOx) slopes as ozone production efficiencies. The greater NOy depletion during the highest ozone events observed at Baxter imply that peak ozone events are related to longer aging of polluted air mass, and not to variations in ozone production efficiency.

(2) Background ozone concentrations that approach 50 ppb imply that it will be difficult to meet the 8-hour ozone standard of 80 ppb without a strategy to address regional ozone concentrations and reduce this background. An open question is whether the 50 ppb background is because of the mix of emissions over the larger Eastern North American region, or is an external input.

(3) The NEOPS upper-air data set provides a validated and internally consistent resource for placing surface observations in a more regional context and for testing and validating models.

(4) The NEOPS data set can, in many instances, be viewed as a useful test bed for ozone and haze rule policy relevant research.

(5) Although westerly transport influences air quality in the U.S. East Coast during ridge-induced stagnation ozone/haze pollution episodes, the influence (emissions and microscale transport effects) of the urban corridor itself may substantially contribute to ozone and haze formation.

(6) The value of an integrated data set for evaluation and testing of state-of-the-art chemical transport models, and for understanding physical/chemical processes, has been demonstrated.

(7) Comparison of aircraft and surface network data with satellite products yields a previously untapped wealth of extremely useful information with respect to regional transport and climatic effects.

(8) The spatial extent of the airshed for ozone and particulate matter implies that only through regional planning organizations (RPOs) would we be able to devise effective means of reducing pollution in the Eastern United States. Until such a regional perspective is adopted and RPOs are implemented, it will be difficult to evaluate the relative efficacies of individual, low-level emission reduction strategies that vary from one location to another in improving air quality.

(9) Because ozone can be transported several hundred kilometers downwind of its source region over this time scale, depending on upper-level winds, effective ozone control strategies need to take into consideration the spatial scales ranging from local to regional, and time scales on the order of several days.

(10) An examination of the photochemical model's response to changes in the emissions inventory reveals that the choice of equally valid boundary-layer parameterizations can significantly influence the efficacy of emission reduction strategies.

(11) The successes in comparisons between models and measurements has increased the confidence in the use of these models by state and federal regulatory agencies for emission control strategy development and evaluation; however, many features are still described inadequately.

NEOPS Success Relative To Expected Results. The original objectives and plan for the NEOPS program are outlined in the first section of Part A of this document. By reviewing the original plan prepared 5 years ago, and comparing that plan and its expected results with the actual results that have been accomplished, we can see a measure of the success of this undertaking. The expected results and benefits of the proposed research included the following item from the proposal submitted in 1997: (1) advancement in our understanding of the physical, chemical, and meteorological factors that influence formation and accumulation of fine particulate mass in large east coast cities; (2) unambiguous source identification and attribution for fine mass, including local, distant, and regional sources of carbonaceous and non-carbonaceous aerosols; (3) differentiation between the contributions of primary and secondary, natural and anthropogenic sources to the fine mass concentrations in an urban area; (4) a rich database for examining linkages between factors affecting the spatial and temporal variability, vertical and horizontal transport, and formation rates of ozone and fine mass; and (5) the development, description, and qualification of new tools for fine mass sampling and measurement, which will represent all the ambient particle mass (including SVOC and nitrates) with specifiable reliability and minimal losses of semivolatile and unstable components of fine mass.

From today's perspective, we generally have been successful in all of these topics, with the possible exception of Objective 2. The unambiguous source identification is more difficult than originally envisioned. We have been successful in identifying some parts of that goal; we have observed the transport of air masses transported from outside our region (from the Midwest region) that were significant contributors to ozone and PM during pollution episodes (in fact these are the important contributors to major events). We also have observed periods with vertical mixing, adding pollutants and precursors to the surface layer from transported air masses aloft. We also have observed the effect of local sources; for example, the afternoon rush hour traffic frequently is observed to reduce the local ozone because of titration by freshly generated NOx. Unfortunately, most of the data on the particulate matter measured during the intensives has just become available and much has not yet been plotted and analyzed. The answers to source identification questions may still be addressed with the NEOPS data set.

This study has provided a major advancement in efforts to characterize and understand the physico-chemical processes governing ozone and fine particle formation, transport, and fate. The results allow us to develop and evaluate state-of-the-art techniques for aerosol characterization and permit investigations into source identification and apportionment. The results obtained provide answers to the key scientific questions and provide the foundation for basic decisions considered by the EPA as it addresses critical issues of regulation to protect the at-large population from undue health stresses from air pollution. The measurements provide a unique data set because of the multi-dimensional pictures developed to observe the physical processes that control the evolution of air pollution episodes. The uniqueness of these results comes from the combination of remote sensing instruments with instrumented balloon and aircraft payloads employed in these investigations, which provide the most detailed measurements of the vertical structure available. The time sequences of vertical profiles of the ozone, PM, and meteorological properties will be necessary for evaluation of the models that currently are under development.

The planned measurement programs have been completed and essentially all of the data reduction is complete. Even though several papers have been published that make use of the results, most of the efforts to interpret the results remain to be accomplished. Several of the interesting studies were delayed because some results are just now becoming available. The analysis and interpretation activities likely are to continue for several years. A no-cost extension was applied for and the efforts that were suspended in April 2002 are expected to begin again soon. The primary items remaining to be accomplished are:

(1) Completion, as well as format, of the database for submission to the national archive through the NARSTO archive. Most of the results have been received from the investigators and most of those are complete but need review and formatting before submission. We expect that this effort will be completed in about 6 months and sufficient funds are remaining to accomplish the task.

(2) Completion of the project with a major science workshop where colleagues in the community could see an overview of the results and be introduced to the database. The original plan was to hold that workshop in conjunction with the EPA-sponsored "Air Toxics" meetings, but those meetings have been discontinued. Because we do not have the resources within the program to conduct such a workshop, we have chosen to present results at two Air Chemistry Workshops sponsored by the American Meteorological Society. If there is another opportunity to present the results to the EPA community, we would try to do that.

(3) Preparation and publication of a handbook on program results. The primary results, several of the papers, and an introduction/overview of the database will be included in the volume. This would be completed during the summer of 2003 using the project resources planned for that activity. Additional support will be sought for publication costs.


Journal Articles on this Report : 20 Displayed | Download in RIS Format

Other project views: All 194 publications 26 publications in selected types All 20 journal articles
Type Citation Project Document Sources
Journal Article Athanassiadis GA, Rao ST, Ku J-Y, Clark RD. Boundary layer evolution and its influence on ground-level ozone concentrations. Environmental Fluid Mechanics 2002;2(4):339-357. R826373 (2002)
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  • Journal Article Chandrasekar A, Philbrick CR, Clark R, Doddridge B, Georgopoulos P. A large-eddy simulation study of the convective boundary layer over Philadelphia during the 1999 summer NE-OPS campaign. Environmental Fluid Mechanics 2003;3(4):305-329. R826373 (2002)
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  • Journal Article Chandrasekar A, Philbrick CR, Clark R, Doddridge B, Georgopoulos P. Evaluating the performance of a computationally efficient MM5/CALMET system for developing wind field inputs to air quality models. Atmospheric Environment 2003;37(23):3267-3276. R826373 (2002)
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  • Journal Article Chandrasekar A, Russell Philbrick C, Doddridge B, Clark R, Georgopoulos P. A comparison study of RAMS simulations with aircraft, wind profiler, lidar, tethered balloon and RASS data over Philadelphia during a 1999 summer episode. Atmospheric Environment 2003;37(35):4973-4984. R826373 (2002)
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  • Journal Article Chandrasekar A, Philbrick CR, Doddridge B, Clark R, Georgopoulos PG. A comparative study of prognostic MM5 meteorological modeling with aircraft, wind profiler, lidar, tethered balloon and RASS data over Philadelphia during a 1999 summer episode. Environmental Fluid Mechanics 2005;4(4):339-365. R826373 (2002)
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  • Journal Article Chen L-WA, Doddridge BG, Dickerson RR, Chow JC, Mueller PK, Quinn J, Butler WA. Seasonal variations in elemental carbon aerosol, carbon monoxide and sulfur dioxide:implications for sources. Geophysical Research Letters 2001;28(9):1711-1714. R826373 (2002)
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  • Journal Article Chen L-WA, Doddridge BG, Dickerson RR, Chow JC, Henry RC. Origins of fine aerosol mass in the Baltimore–Washington corridor:implications from observation, factor analysis, and ensemble air parcel back trajectories. Atmospheric Environment 2002;36(28):4541-4554. R826373 (2002)
    R826238 (2001)
    R826238 (Final)
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  • Journal Article Clark RD. Using GEMPAK/GARP in undergraduate research. Bulletin of the American Meteorological Society 2002;83(2):178-180. R826373 (2002)
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  • Journal Article Eatough DJ, Obeidi F, Pang YB, Ding Y, Eatough NL, Wilson WE. Integrated and real-time diffusion denuder sampler for PM2.5. Atmospheric Environment 1999;33(17):2835-2844. R826373 (1998)
    R826373 (2000)
    R826373 (2002)
    R825367 (Final)
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  • Journal Article Hallock-Waters KA, Doddridge BG, Dickerson RR, Spitzer S, Ray JD. Carbon monoxide in the US Mid-Atlantic troposphere:evidence for a decreasing trend. Geophysical Research Letters 1999;26(18):2861-2864. R826373 (2002)
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  • Journal Article Kleinman LI, Daum PH, Imre D, Lee Y-N, Nunnermacker LJ, Springston SR, Weinstein-Lloyd J, Rudolph J. Ozone production rate and hydrocarbon reactivity in 5 urban areas:a cause of high ozone concentration in Houston. Geophysical Research Letters 2002;29(10):105-1–105-4. R826373 (2002)
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  • Journal Article Kleinman LI, Ryan WF, Daum PH, Springston SR, Lee Y-N, Nunnermacker LJ, Weinstein-Lloyd J. An ozone episode in the Philadelphia metropolitan area. Journal of Geophysical Research-Atmospheres 2004;109(D20):D20302 (17 pp.). R826373 (2002)
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  • Journal Article Ku J-Y, Mao H, Zhang K, Civerolo K, Rao ST, Philbrick CR, Doddridge B, Clark R. Numerical investigation of the effects of boundary-layer evolution on the predictions of ozone and the efficacy of emission control options in the Northeastern United States. Environmental Fluid Mechanics 2001;1(2):209-233. R826373 (2000)
    R826373 (2002)
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  • Journal Article Lin C-YC, Jacob DJ, Munger JW, Fiore AM. Increasing background ozone in surface air over the United States. Geophysical Research Letters 2000;27(21):3465-3468. R826373 (2000)
    R826373 (2002)
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  • Journal Article Mihailovic DT, Rao ST, Hogrefe C, Clark RD. An approach for the aggregation of aerodynamic surface parameters in calculating the turbulent fluxes over heterogeneous surfaces in atmospheric models. Environmental Fluid Mechanics 2002;2(4):315-337. R826373 (2002)
    R828733 (2001)
    R828733 (2003)
    R828733 (Final)
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  • Journal Article Mihailovic DT, Rao ST, Alapaty K, Ku JY, Arsenic I, Lalic B. A study on the effects of subgrid-scale representation of land use on the boundary layer evolution using a 1-D model. Environmental Modelling & Software 2005;20(6):705-714. R826373 (2002)
    R828733 (2001)
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  • Journal Article Novitsky EJ, Philbrick CR. Multistatic lidar profiling of urban atmospheric aerosols. Journal of Geophysical Research-Atmospheres 2005;110(D7):D07S11 (16 pp.). R826373 (2002)
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  • Journal Article Stehr JW, Dickerson RR, Hallock-Waters KA, Doddridge BG, Kirk D. Observations of NOy, CO, and SO2 and the origin of reactive nitrogen in the eastern United States. Journal of Geophysical Research: Atmospheres 2000;105(D3):3553-3563. R826373 (2002)
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  • Journal Article Zhang KS, Mao HT, Civerolo K, Berman S, Ku J-Y, Rao ST, Doddridge B, Philbrick CR, Clark R. Numerical investigation of boundary-layer evolution and nocturnal low-level jets:local versus non-local PBL schemes. Environmental Fluid Mechanics 2001;1(2):171-208. R826373 (2000)
    R826373 (2002)
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  • Journal Article Zurer P. Houston culprit: petrochemicals. Air-sampling study fingers reactive olefins as source of excessive ozone. Chemical & Engineering News 2002;80(23):10. R826373 (2002)
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  • Supplemental Keywords:

    air, ambient air, atmosphere, ozone, PM2.5, planetary boundary layer, airshed, atmospheric region of influence, water, global climate, mobile sources, tropospheric, precipitation, chemical transport, meteorological influences on atmospheric pollution, diurnal cycle of polluted air masses, connections between ozone and fine particle sources, dynamical influences on chemical processes, vertical transport, atmospheric chemical reservoirs, exposure, health effects, ecological effects, toxics, particulates, volatile organic compounds, VOC, oxidants, nitrogen oxides, sulfates, urban atmospheric chemistry, pollution monitoring, ozone chemistry sources/sinks, fine particle sources/sinks, regionalization, public policy, decisionmaking, cost benefit, observation, public good, regional factors influencing urban pollution, urban forcing of regional air chemistry, environmental chemistry, physics, meteorology, modeling, monitoring, analytical, surveys, measurement methods, general circulation models, climate models, photochemical models, meteorological model, emission control strategies, satellite remote sensing, MM5, RAMS, LES, CALMET, RASS, Lidar, wind profiler, aircraft, tethered balloon, Models-3/CMAQ, MAQSIP, northeast, Atlantic coast, Chesapeake Bay, Mid-Atlantic, Pennsylvania, PA, Maryland, MD, New Jersey, NJ, Delaware, DE, EPA Region 3, transportation, industry, petroleum., RFA, Scientific Discipline, Air, Geographic Area, Environmental Chemistry, State, Environmental Monitoring, tropospheric ozone, Atmospheric Sciences, emission sources, urban air, remote sensing, ambient ozone data, ozone occurrence, Pennsylvania, ambient air, air pollution models, diurnal cycle of polluted air masses, fine particle sources, atmospheric chemical reservoirs, meteorological fluctuations, PA

    Relevant Websites:

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    Progress and Final Reports:

    Original Abstract
  • 1998 Progress Report
  • 1999 Progress Report
  • 2000 Progress Report
  • 2001
  • Final