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Highlights
Past Highlights
December 2006
New York City Urban Dispersion Model Evalualtion Project.
The Atmospheric Sciences Modeling Division collaborated with the Department of Homeland Security's New York City Urban Dispersion Program to evaluate fine-scale models for urban environments. The project is part of an interagency program involving the Department of Homeland Security, the National Oceanic and Atmospheric Administration (Department of Commerce), Department of Defense, Department of Energy, and the Environmental Protection Agency. Two major field campaigns were conducted in Midtown Manhattan during 2005, resulting in a quality-assured database of urban winds (from 12 surface anemometers) and tracer dispersion (from 64 surface concentration monitors). The modeling team is now conducting model evaluation studies using these data and a building database (originally produced by Vexcel Corporation in 2001) that Division scientists had extensively revised and updated.
A Division scientist has applied the computational fluid dynamics FLUENT software to simulate urban meteorology and tracer transport with 1 meter resolution for several of the intensive observation periods from the Midtown Manhattan field studies. The Urban Dispersion Program manager will compare these modeling results with modeling result from other collaborators. Each local urban scale model being evaluated has some different features, both in the resolved scale and the physical process modules. Figure 1 presents an example simulation showing the detailed changes in wind direction throughout the study area centered near Times Square and Rockefeller Center. These modeled winds compare very well with the field observed winds.
The model evaluation plan is to complete the present two "setup" simulations, followed by four "blind" simulations of the Midtown Manhattan field studies. The "setup" simulations allow the use of meteorological and tracer field data in setting up the model simulation. The "blind" simulations will be conducted with only the meteorological data being provided to the modelers to assist in defining model boundary conditions. A goal of these model evaluation studies is to assess the accuracy of fine-scale computational fluid dynamics modeling in complex urban building environments, and their possible role in supporting homeland security. (alan.huber@noaa.gov)
Top-down Evaluation of NOx Emissions: Inverse Modeling. A method was developed based on the discrete Kalman filter inversion technique (inverse technique) for using satellite nitrogen dioxide (NO2) column observations to check for biases in current emission inventories of nitrogen oxides (NOx). To calculate sensitivities of the NO2 column to NOx emissions for the inverse technique, the decoupled direct method in 3D (DDM‑3D) and the Community Multiscale Air Quality (CMAQ) model have been used. This approach advances the previous inverse methodology by integrating the strengths of DDM-3D and the discrete Kalman filter inverse method. The method was tested using various pseudodata or synthetic scenarios and promises to be a robust and computationally efficient procedure for evaluating and estimating NOx emissions with satellite observations and the CMAQ model. As satellite data retrieval techniques continue to improve, top-down inverse modeling could lead to reductions in the uncertainty of emissions inventories used in regional scale air quality models. (sergey.napelenok@noaa.gov, alice.gilliland@noaa.gov, rob.pinder@noaa.gov)
SCIENTIFIC ACCOMPLISHMENTS
Wind Tunnel Simulations of Near-roadway Dispersion: Urban Boundary Layer Specification. Findings from recent epidemiological studies near major roadways have increased interest in the dispersion of pollutants and their potential impacts on nearby residents. The Division is conducting a series of wind-tunnel studies to examine how roadway configurations and nearby structures affect the distribution of traffic-related pollutant concentrations within a few hundred meters of major urban roadways. The first phase of these studies was conducted to develop the experimental set-up necessary to simulate boundary layer conditions in the wind tunnel that will adequately reproduce boundary layer conditions expected in urban, near-roadway locations. Measurements taken in the experimental set-up correspond to values typical of an urban area dominated by multi-story buildings. This boundary layer experimental set-up will be used for all roadway scenarios to be examined in this study. This work is begin conducted as part of EPA’s Near Roadway Research Initiative. (steven.perry@noaa.gov, david.heist@noaa.gov)
Characterizing the Dispersion of Traffic Emissions Around Noise Barrier in the Near-Road urban Environment: A Comparison Between Mobil Measurements and Fine-Scale Simulations. Understanding the dispersion of pollutants from mobile traffic sources, particularly in the near-field is important both for urban planning and for air quality assessments. Predicting pollutant concentration patterns in complex environments depends on accurate representations of local features affecting near-field (<300 m) pollutant transport and dispersion. A study was conducted examining the effects of roadside noise barriers on the flow patterns and dispersion of pollutants from a high-traffic highway in an urban area of Raleigh, NC, when the wind was normal to the road. The effect of the noise barrier was analyzed using the fine-scale wind field and dispersion model QUIC (Quick Urban & Industrial Complex). Model simulations were found to compare favorably with the near-road spatial distributions of ultra-fine particulates from vehicular emissions measured using a mobile platform.
The essential features of the measured pollutant patterns are reproduced by the model, though minor differences are seen in the absolute concentration magnitudes and rates of decay with distance. The major preliminary findings are as follows:
- Elevated concentration levels occur in the plume as it encounters, and moves up and over the sound barrier.
- A recirculation wake region is present in the lee of the barrier, and concentrations are significantly reduced (~50%) compared to an open area equidistant from the roadway.
- When the elevated plume encounters other downwind obstacles (e.g. trees or buildings usually associated with sound barriers) increased mixing and decreased concentrations are found.
These results are being assembled in a technical paper by George Bowker, Rich Baldauf, Vlad Isakov, Andrey Khylstov, and Bill Petersen, “Application of the Quick Urban & Industrial Complex (QUIC) model to characterize the effects of sound barriers and vegetation on the dispersion of pollutants from roadways”. The paper is undergoing internal review.(vlad.isakov@noaa.gov, Geoge Bowker)
Assessing Air Toxics Concentrations in Urban Areas using Mobile Platform Measurements. Division staff is collaborating with researchers from Duke University to develop and apply a method to characterize air toxics concentrations in urban areas using results from a recently-conducted field study in Wilmington, Delaware. This method may be useful for future air toxic assessments in Environmental Justice applications, epidemiological studies, and environmental health risk assessments. The method uses mobile monitoring, which provides a capability that is unavailable from stationary monitor measurements. Mobile monitoring can be used to provide spatial mapping, as a diagnostic tool to supplement existing monitoring networks or to assist in siting future monitors, and to help determine the relative importance of local versus regional impacts. An application of the method is presented in a technical paper drafted by Vlad Isakov, Jawad Touma, and Andrey Khylstov, “A Method of Assessing Air Toxics Concentrations using Mobile Platform Measurements”. The paper is currently in NOAA review. (vlad.isakov@noaa.gov)
Improvement to the Aqueous Chemistry (AQCHEM) in Community Multiscale Air Quality (CMAQ). Secondary particulate matter formation through cloud processing is well documented for sulfate. Growing evidence suggests that cloud processing is also an important source of secondary organic aerosol (SOA). Twenty organic oxidation reactions were added to CMAQ’s aqueous chemistry (AQCHEM) subroutine. In-cloud SOA formation from the oxidation of two water-soluble aldehydes (glyoxal and methylglyoxal) is simulated. The Division is conducting box model testing of the revised AQCHEM subroutine. (ann.carlton@noaa.gov)
CONFERENCES & WORKSHOPS
31st Annual EPA-A&WMA Information Exchange, Environmental Protection Agnecy, Research Triangle Park, North Carolina, December 5, 2006. Russell Bullock attended this conference, and gave a presentation entitled ARegional-Scale Atmospheric Mercury Modeling."
2006 Fall Meeting of the American Geophysical Union, San Francisco, California, December 11-15, 2006. William Hutzell and Robert Pinder attended this meeting. William gave a presentation entitled APredicting The Fate and Transport of Toxic Metal Emissions Over the United States. (rob.pinder@noaa.gov, Bill Hutzell)
Air Toxics Training Workshop. Several Division staff members participated in the Air Toxics Training Workshop in Durham, North Carolina on December 12-14, 2006. This workshop provided a forum for EPA, State, Local, and Tribal pollution control personnel to share ideas and exchange information on current and future air toxics programs. (vlad.isakov@noaa.gov, thomas.pierce@noaa.gov)
CMAQ Peer Review Meeting, Environmental Protections Agency, Research Triangle Park, North Carolina, December 18-20, 2006. A Peer Review panel conducted a scientific review of the CMAQ model system development, applications, and evaluation at EPA, RTP during December 18-20. The seven panel members included Dr. Anantha Aiyyer (North Carolina State Univ.), Dr. Daniel Cohan (Rice Univ.), Dr. Armistead Russell (Georgia Tech), Dr. William Stockwell (Howard University), Dr. Saffet Tanrikulu (Bay Area Air Quality Management District), Dr. William Vizuete (Univ. of NC-Chapel Hill), and Dr. James Wilczak (NOAA/ESRL). Division staff members made presentations and held fruitful discussions with the panelists during the first two days of the meeting. The panel’s preliminary assessments were quite positive. A final report on their evaluation will be available in the March/April timeframe. (kenneth.schere@noaa.gov)
Expert Workshop under the UNECE Convention on Long-range Transboundary Air Pollution, Atmospheric Ammonia: Detecting Emission Changes and Environmental Impacts, Edinburgh, Scotland, December 406, 2006. Robert Pinder attended this meeting and presented a poster entitled “Detecting the Impact of Emission Reductions on Ammonium Nitrate Particulate Matter Using Observable Indicators. (rob.pinder@noaa.gov)
International Converence on Atmospheric Chemistry, Davis, California, December 6-8, 2006. Deborah Luecken co-organized the International Conference on Atmospheric Chemistry, and moderated the final panel session. She presented a paper entitled "Effects of using the CB05 vs. SAPRC99 vs. CB4 Chemical Mechanism on Model Predictions." This paper included results from recent CB4-CB05-SAPRC99 analyses and comparisons by the Division and the Environmental Protection Agency's Office of Air Quality and Planning Standards. Kenneth Schere gave a presentation entitled "Accuracy and Cost Considerations in Choosing a Chemical Mechanism for Operational Use in AQ Models." He also participated in a panel session discussing future needs and directions in chemical mechanism research. (Deborah Luecken, kenneth.schere@noaa.gov)
Joint (Interagency) Action Group on Wildland Fire Weather Needs Assessment. On December 12, 2006, the Division represented EPA at a meeting held at the Office of the Federal Coordinator for Meteorology (OFCM) in Silver Spring, Maryland. The purpose of the meeting was to begin discussion on survey responses received from several hundred individuals across the nation on needs related to wildland fires. Beginning in February 2007, the Joint Action Group (JAG) on National Wildland Fire Weather Needs Assessment (NWFWNA) will use the survey results to begin synthesizing and assessing federal agency needs. More information on the JAG can be found at www.ofcm.gov/jag-nwfwna/. (thomas.pierce@noaa.gov)
VISITORS
Dr. John McHenry
Chief Scientist
Baron Advanced Meteorological Systems (BAMS)
North Carolina State University
Raleigh, North Carolina
Dr. John McHenry visited on December 19, 2006, and worked with Division staff to test a version of the Weather Research and Forecasting with Chemistry (WRF/Chem) model that BAMS researchers had modified to incorporate both the Sparse Matrix Operator Kernel Emissions (SMOKE) emissions processing system and the EDSS/Models-3 Input/Output Applications Programming Interface (I/O API; a.k.a. M3IO). Successful tests of the BAMS code were conducted on the Division=s HPCC computer systems. The model building and testing procedures will be streamlined before submitting the WRF/Chem with SMOKE and M3IO source code to the WRF/Chem repository for use by the air quality research community. (jerry.herwehe@noaa.gov, kenneth.schere@noaa.gov)
Fire Emissions Research at NASA Langley. On December 5, 2006, Dr. Amber Soja, research scientist at the NASA Langley Research Center in Langley, Virginia, met with Division staff to discuss a collaboration to develop and evaluate wildland fire emission estimates using satellite-based procedures. (thomas.pierce@noaa.gov)
A Pilot Geospatial Analysis of Exposure to Air Pollutants (with Special Attention to Air Toxics) and Hospital Admissions to Harris County, Texas. On December 15, 2006, Dr. Winifred Hamilton of Baylor’s College of Medicine visited EPA’s National Environmental Research Laboratory (NERL) in Research Triangle Park, North Carolina. Dr. Hamilton is the Principal Investigator of a National Urban Air Toxics Research Center (NUATRC) funded study, “A Pilot Geospatial Analysis of Exposure to Air Pollutants (with special attention to air toxics) and Hospital Admissions in Harris County, Texas.” This goal of this study is to incorporate results from an air toxics version of the Community Multiscale Air Quality (CMAQ) modeling system to provide the ambient air toxics concentrations component of the exposure analyses. The purpose of her visit was to meet with key Division and NERL scientists involved in exposure modeling. (jason.ching@noaa.gov)