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List of NEOPS-DEP Publications/Abstracts
Published Papers:
83rd American Meteorological Society 5th Conference on Atmospheric Chemistry (Long Beach, California, Feb.8-12, 2003)
ADVANCES IN UNDERSTANDING URBAN AIR POLLUTION FROM THE NARSTO-NEOPS PROGRAM
C. Russell Philbrick, Penn State University, University Park, PA 16802., William F. Ryan, Richard D. Clark, Bruce G. Doddridge, Philip Hopke, and Stephen R. McDow.
The NARSTO-NE-OPS (North East Oxidant and Particle Study) is an investigation of the coupling of the meteorological and chemical processes that control the evolution of air pollution events. The project includes four major field programs which have been carried out at a field site in northeast Philadelphia during the summers of 1998, 1999, 2001 and 2002. The activity brings together the research groups from several universities and government laboratories to apply advanced measurement techniques for understanding the physical and chemical processes contributing to air quality issues. During the 21 cumulative weeks of summer field intensives, the meteorological and chemical characteristics attending a wide range of atmospheric processes were observed. The results confirm that a three-dimensional regional scale picture of the atmosphere is essential to understanding air pollution events. Vertical profiles of atmospheric properties are needed to properly model and predict ozone and particulate matter pollution because of the significance of horizontal transport aloft and vertical mixing processes on the development and evolution of important periods of air pollution. Efforts have also focused on development and testing of several new approaches to improve measuring techniques for better understanding of the physical and chemical properties of the airborne particulate matter.
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SUMMARY OF METEOROLOGICAL CONDITIONS DURING THE NORTHEAST OXIDANT AND PARTICULATE STUDY (NEOPS-DEP) JULY 2002 INTENSIVE OBSERVING PERIOD
William F. Ryan, Penn State University, University Park, PA 16802., C. Russell Philbrick, and Richard D. Clark.
This paper will summarize the key weather features observed during the July 2002 North East Oxidant and Particle Study (NEOPS) Intensive Observing Period (IOP). Several episodes of enhanced concentrations of ozone and fine particles were observed during this IOP and will be examined in more detail with respect to synoptic and mesoscale phenomena associated with these episodes. In particular, an intense smoke and haze event occurred on July 7-9 associated with wildfires in northern Quebec. This episode was characterized by unusually high concentrations of fine particulate matter and localized areas of high ozone concentrations as well.
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THE INFLUENCE OF CANADIAN WILDFIRES ON AIR QUALITY IN PHILADELPHIA PA DURING NE-OPS-DEP
Richard D. Clark, Millersville University, Millersville, PA 17551-0302., Cheol-Heon Jeong, and C. Russell Philbrick.
On 6-7 July 2002 a nearly stationary upper level low over Maine produced an extended fetch of northerly flow that transported smoke into the mid-Atlantic and New England regions from wildfires 1500 kilometers north of Philadelphia, PA, where an air quality study was being conducted. Continuous measurements of trace gas concentrations (CO, SO2, O3, NO/NO2/NOX), fine particle mass from three ambient samplers (TEOM, CAMM, and RAMS), EC/OC, b scattering coefficients of total particulates and dry PM2.5, and conventional meteorological data were collected at the surface, while a tethered balloon and RASS profiler were used to document aloft distributions of PM2.5, virtual temperature, and wind velocity.
The smoke plume radically altered the local atmospheric and air quality conditions around Philadelphia. While trace gas concentrations remained relatively low (e.g., O3 < 50 ppbv; SO2 < 5 ppbv on 6 July) under steady, brisk northerly flow from Canada and reduced solar irradiance, CO concentrations, total scattering coefficients, and fine particle mass increased rapidly by factors of 5-10 with a concurrent decrease in visibility to one kilometer within an hour after the onset of the event. Contrary to forecasts calling for a period of dry continental air, relative humidity remained elevated at 60% even as temperatures on both days peaked at 32 C. The increased moisture and high concentrations of fine particles resulted in aloft concentrations of PM2.5 nearly an order of magnitude greater (0.6 mg/m3) than those typically observed for a day with deleterious air quality (0.06 ? 0.2 mg/m3).
Preliminary results are presented that provide key insights into the degradation of an otherwise clean, dry, continental air mass due to the injection of smoke from wildfires. The 6-7 July smoke event provides an interesting study of the effects of particles on the degradation of air quality and visibility without being contaminated by the influence of high criteria gas concentrations and their precursors.
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ORGANIC COMPOUNDS MEASURED IN PM2.5 DURING NEOPS
Tadeusz E. Kleindienst, ManTech Environmental Technology, Inc., Research Triangle Park, NC 27713., Christopher D. McIver, and Edward O. Edney.
The organic fraction of fine particulate matter (PM2.5) in ambient environments is composed of non-polar and polar compounds. While many studies have examined the non-polar component, on average it accounts for only 10-25% of the organic mass. Polar organic compounds can come from gas-to-particle conversion of oxidation products of natural and anthropogenic hydrocarbons and from wood combustion. Only a limited number of studies have been conducted to examine this component of ambient PM2.5.
A study of the ambient aerosol was undertaken in Philadelphia, PA, USA during the summer of 2001 as part of NEOPS. The goal was to measure the overall polarity of PM2.5 and to identify classes of particle-bound polar oxygenates, and where possible individual compounds, containing carbonyl and hydroxyl functional groups. PM2.5 samples were collected and analyzed for gravimetric mass, inorganic composition by ion chromatography, polar oxygenated compounds by gas chromatography-mass spectroscopy, and the total organic and elemental carbon by a thermal-optical method. The chemical analyses also included determining the polarity of the PM2.5 by measuring the organic carbon concentrations in a series of extraction solvents of increasing polarity. Detailed analysis of the organic carbon was undertaken using a double derivatization technique with PFBHA for the derivatization of carbonyl groups and BSTFA for hydroxyl groups. Organic and elemental carbon were measured from aerosol collections onto quartz filters.
The study was carried out for a five day period from 22-27 July 2001. Integrated filter samples were taken for two 24-hour and one 48-hour sampling periods. Gravimetric results indicated total mass loadings from 14 to 21 µg m-3 for the sampling periods during that time frame. The organic mass was found to comprise 34% of the total gravimetric mass. Organic carbon analysis of the hexane extract indicated that 25% of the organic carbon was nonpolar. The mass spectra data were consistent with the presence of the following classes of oxygenates: oxo mono carboxylic acids, trihydroxy monocarboxylic acids, normal dicarboxylic acids, oxo dicarboxylic acids, hydroxy dicarboxylic acids, methoxy dicarboxylic acids, dihydroxy dicarboxylic acids, tricarboxylic acids, and photooxidation products of a-pinene and toluene in the PM2.5. The detailed analysis of the organic fraction at the site suggested the presence of chemical markers related to photooxidation products of aromatic hydrocarbons.
Disclaimer: This work has been funded fully, or in part, by the United States Environmental Protection Agency, under Contract Number 68-D5-0049 to ManTech Environmental Technology, Inc. It has been subjected to Agency review and approved for publication.
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MODIFICATION OF SURFACE AND BOUNDARY LAYER METEOROLOGY AND CHEMISTRY BY SEABREEZE INCURSIONS DURING NE-OPS
Richard D. Clark, Millersville University, Millersville, PA 17551-0302.
Seabreeze circulations have the ability to significantly modify the atmospheric boundary layer by replacing the existing air mass with low level incursions of cool, moist air, elevated wind speed, and changes in wind direction that can either increase or diminish the concentrations of chemical constituents depending on the relative difference between the in-situ and upstream properties. The NE-OPS Philadelphia site is near the western fringe of mid-Atlantic seabreeze intrusions (~ 50-100 km), and several propagated through the site during the 1999 and 2002 summer field intensives and were documented using the suite of instruments, including Raman lidar, tethersondes, profiler/RASS, and surface particulate and trace gas analyzers. Common to all seabreeze events is the sudden (~ 1-10 minutes) rise in relative humidity to near saturation, and the concurrent increase in optical extinction (total and back scatter coefficients) with the formation of haze droplets on existing aerosols. Measurements show that temperatures declined by several degrees and wind speed increased by factors of 2-3 as the shallow (100 – 300 m) air mass propagated through the site. The effect on ozone and other trace gas concentrations depends on the relative differences between the two air masses. Case studies are presented that show some episodes where ozone concentrations were reduced by nearly a factor of two (e.g., 165 to 95 ppbv), and other cases where ozone increased as the seabreeze front replaced drier, cleaner continental air. Doppler radar displays show that as the seabreeze continues westward, its length, intensity, and signature reflectivity diminishes, eventually becoming indistinguishable in the surrounding air mass, while conditions within the cool, moist air mass are sustained for hours after passage. The depth, propagation speed, and timing of the seabreeze are crucial to prediction of pollution episodes. Operational numerical models are capable of simulating the seabreeze circulation, but generally fail to accurately capture the depth and timing of these events at locations well removed from coastal regions, where they still can exhibit a significant influence on the local meteorology and chemistry.
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LOW LEVEL JETS OVER THE MID-ATLANTIC REGION DURING NE-OPS 1999–2002
Richard D. Clark, Millersville University, Millersville, PA 17551-0302., Richard Walker Jr., Dennis O'Donnell, Eric Hohman, and Dale Unruh.
A number of nocturnal low level jets (LLJ) were documented during the NE-OPS summer intensives of 1999 and 2002. These low-level wind maxima are most pronounced when embedded in southerly, mountain-parallel, synoptic flow, and enhanced by differential heating/cooling under clear sky conditions from the coastal plain to the Piedmont. LLJs are a mesoscale phenomenon with horizontal dimensions on the order of a few hundred kilometers, residing at the top of the nocturnal boundary layer (NBL) typically between 400-800 meters AGL, and exhibiting wind speeds in excess of 15 m/s – nearly twice the geostrophic value. In summers 1999 and 2002, several LLJs were observed by the profiler/RASS at the Philadelphia NE-OPS site, along with simultaneous aloft measurements of water vapor mixing ratio, ozone concentration, temperature, and optical extinction using the Raman lidar, and measurements of meteorological variables, ozone concentration, and PM2.5 using tethered balloons. These observations document the influence that LLJs have on modifying the properties of the residual boundary layer as the inertial oscillation of the ageostrophic wind ensues. As the LLJ rotates from southerly to south-westerly or westerly, incursions of drier air, often with elevated ozone concentrations representative of western source regions, are transported hundreds of kilometers. Periodically, excessive shear below the level of maximum wind speed will induce downward momentum transport resulting in a bursting event at the surface and short-period increases in ozone and PM concentrations. As operational numerical models incorporate more sophisticated boundary layer parameterizations and higher vertical resolution, the general features of LLJs are being simulated. Observations and measurements obtained during NE-OPS LLJ episodes will be compared to Eta-model forecasts. In 2002 especially, Eta forecasts of nocturnal LLJs agreed remarkably with observations and were used with confidence as guidance for these events.
BOUNDARY LAYER EVOLUTION OVER PHILADELPHIA, PA DURING THE 1999 NARSTO-NE-OPS PROJECT: COMPARISON OF OBSERVATIONS AND MODELING RESULTS
Kevin L. Civerolo, New York State Department of Environmental Conservation, Albany, NY 12233-3259., Jia-Yeong Ku, Bruce G. Doddridge, Richard D. Clark, and Gopal Sistla.
The evolution and structure of the planetary boundary layer (PBL) are critical to understanding the formation and fates of ozone (O3), particulate matter (PM), regional haze, and respective precursors. As part of the NE-OPS 1999 field campaign, vertical profiles of temperature, humidity, and trace chemical species were made from an instrumented light aircraft at several locations in the US Mid-Atlantic region during July and August. Temperature and humidity profiles were also obtained from a tethered balloon and radiosondes launched at the core surface site, the Baxter Water Treatment Plant. The meteorological observations and PBL height estimates were then compared with the results from two model simulations using the Fifth-Generation Penn State University/NCAR Mesoscale Model (MM5 Version 3.3). The MM5 domain covered much of the eastern US with a horizontal grid resolution of 12 km, for the period July 1 – August 3. In one MM5 simulation, we used the Blackadar PBL scheme, while in the other we used the Gayno-Seaman PBL scheme. Both PBL schemes are commonly used in conjunction with photochemical models to simulate concentrations of O3 and PM. We focus on comparing the PBL heights and vertical profiles of temperature and specific humidity, to investigate the differences in the PBL evolution between these two schemes. Substantial differences between the two model simulations occurred within the lowest 2-3 km of the atmosphere, which are expected to impact such photochemical predictions. While the model tends to predict afternoon mixing heights fairly well, it also tends to fail at night and during the morning evolution. Hence, while the model may be useful in hindcasting weather associated with O3/PM/haze, improvements are needed during the nighttime (nocturnal inversions, low-level jet development) and morning hours (PBL growth and entrainment dynamics).
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Examination of the Influence of a Frontal Passage on Air Pollution Episodes
Sameer Unni1, C. Russell Philbrick1, William F. Ryan1, and Richard D. Clark2. (1) Penn State University, University Park, PA 16802, (2) Millersville University, Millersville, PA 17551-0302
The PSU Raman lidar has been used to observe and analyze various events involving the influence of the passage of meteorological fronts on air quality in the northeast region. One specific event of interest occurred on July 10,1999. During the course of this event, an increase in the concentration of ozone and particulate matter (PM) is observed ahead of a front. As the front enters the region from the Appalachians, a large accumulation of ozone and PM occurs during the afternoon. As the front approaches closer to the site, an increase in water vapor concentration is observed. The arrival of the front at about 0530 UTC is marked by wind gusts accompanying a significant gravity wave, which is evident in the water vapor concentration. With the incursion of the dry air mass by 1440 UTC, the water vapor concentration decreases rapidly to half of its original value. The Raman lidar is demonstrated as an effective tool for discerning the fine scale structure associated with frontal passage. Studies of these variations should be included to improve our understanding of sub-grid scale physics of frontal activity. This event serves as a good description for several cases where air pollution episodes are significantly influenced by frontal activity.
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Development of an Air Pollution Event during the NEOPS-DEP 2002 Investigation
Adam Willitsford1, Jason P. Collier1, Sameer Unni1, Sachin J. Verghese1, C. Russell Philbrick1, Dennis O'Donnell2, Eric Hohman2, Dale Unruh2, Richard Walker3, and Richard D. Clark2. (1) Penn State University, University Park, PA 16802, (2) Millersville University, Millersville, PA 17551-0302, (3) Millersville Univ., Millersville, PA 17551-0302
During the period 30 June to 4 July 2002, several instruments of the NEOPS-DEP project were used to characterize the evolution of an air pollution episode from a site in Philadelphia. The Raman lidar and Radar/RASS profiler from Penn State University and the tethersonde instruments of Millersville University obtained high resolution measurements of the meteorological and atmospheric parameters. The episode persisted for several days and ozone levels exceeded 100 ppb for extended periods on three days. The measurements emphasized the development of a 3-dimensional representation of the air mass using the lidar, radar and sonde measurements to provide vertical profiles of the ozone, particulate matter, water vapor, temperature, optical extinction and wind velocity. The results are used to described the high temporal and spatial characteristics of the episode. One of the features observed was the rapid rise in surface ozone concentrations that occurred at mid-morning on 2 July due to the rapid mixing to the surface from an ozone storage/transport layer aloft.
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Characterization of Nocturnal Jets Over Philadelphia During Air-Pollution Episodes
Sachin J. Verghese, Sriram N. Kizhakkemadam, Adam Willitsford, Jason P. Collier, Sameer Unni, and C. Russell Philbrick. Penn State University, University Park, PA 16802
Raman lidar employed simultaneously with wind measurements of a Radar/RASS profiler can be used to characterize features of nocturnal boundary layer jets (LLJs). While the profiler/RASS measurements document the kinematic and thermodynamic structure by identifying the velocity and virtual temperature distributions, the lidar observations provide high temporal and spatial resolution of the water vapor mixing ratio, temperature, ozone concentration, and optical extinction. Case studies are presented which describe the use of the Penn State University (PSU) Raman lidar and Radar/RASS profiler near Philadelphia during NE-OPS to delineate the physical characteristics of the LLJ, its development and evolution, relationship to the nocturnal inversion and residual boundary layer, and the variations in observed parameters associated with LLJ phenomena. An important finding is the intrusion of drier air, often with elevated ozone concentrations as the LLJ oscillates to become a westerly conveyor of air from the western boundary region in the early morning hours. The periods of well-developed nocturnal jet are highly correlated with the major air-pollution episodes observed during the summer.
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Raman Lidar Measurements of Tropospheric Ozone
P. Jason Collier1, Sameer Unni1, Sachin J. Verghese1, Adam Willitsford1, C. Russell Philbrick2, Richard D. Clark3, and Bruce Doddridge4. (1) Penn State University, University Park, PA 16802, (2) The Pennsylvania State University, (3) Millersville University, Millersville, PA 17551-0302, (4) University of Maryland
Raman lidar techniques have been developed and demonstrated which provide measurements of meteorological properties with high spatial and temporal resolution. The vibrational and rotational Raman lidar signals provide simultaneous profiles of water vapor, temperature, ozone and optical extinction due to airborne particulate matter. The instrument makes use of 2nd and 4th harmonic generated laser beams of a Nd:YAG laser to provide both daytime and nighttime measurements. The ozone profiles in the lower troposphere are measured using a DIAL analysis of the ratio of the vibrational Raman signals for nitrogen (284 nm) and oxygen (278 nm), which are on the steep side of the Hartley absorption band of ozone. Several data sets have been obtained during the NARSTO-NE-OPS measurement programs and the results from these events have been the subject of several recent investigations. Here the ozone measurements from the lidar have been studied and comparisons made with ground based measurements, tethersonde measurements and aircract measurements. Examples have been selected to show the new level of understanding of air quality investigations that is gained from applications of lidar techniques. These techniques are expected to provide the primary means for profiling meteorological parameters in the future.
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Influence of a Canadian Forest Fire on Measurements of Carbonaceous Compounds in Fine Particulate Matter in July 2002 in Philadelphia
Cheol-Heon Jeong, Doh-Won Lee, Philip K. Hopke
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The Comparison Between Thermal Optical Transmittance Elemental Carbon and Aethalometer Black Carbon Measured at the Multiple Monitoring Sites
Cheol-Heon Jeong, Doh-Won Lee, Eugene Kim, Philip K. Hopke, Robert Gelein
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Measurements of Real-Time PM2.5 Mass and Chemical Compositions in Northeast Philadelphia
Cheol-Heon Jeong, Doh-Won Lee, Eugene Kim, Philip K. Hopke, Robert Gelein
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