EVALUATING OZONE PREDICTIONS FROM PHOTOCHEMICAL MODELS USING NE-OPS 1999 OBSERVATIONS Qing Sun, Anatharaman Chandrasekar, Panos G. Georgopoulos* Environmental and Occupational Health Sciences Institute (EOHSI), a joint project of UMDNJ R. W. Johnson Medical School and Rutgers the State University C. Russell Philbrick Penn State University, Department of Electrical Engineering and Applied Research Laboratory, University Park, PA, USA Bruce Doddridge University of Maryland, Department of Meteorology, College Park, MD, USA 1. INTRODUCTION 2. PROBLEM SPECIFICATIONS The North American Research Strategy for Tropospheric Ozone - North East Oxidant and Particle Study (NARSTO-NE-OPS) is a multiinstitutional collaborative research program set up by USEPA to improve current understanding of the underlying causes for the occurrence (and concurrence) of high ozone and fine particle concentration levels in the North-eastern United States. Various advanced meteorological and air chemistry measurements were made in the vicinity of Philadelphia, Pennsylvania during two field campaigns conducted during the summers of 1998 and 1999 (Philbrick, 2000). Fast et al. (2002) evaluated an Eulerian chemical transport model developed at PNNL against NE-OPS data obtained during the period July 23 to August 11, 1999. The present investigation was primarily focused on a major ozone episode that took place in July 15-19, 1999 over the Philadelphia region, to perform an extensive evaluation of two widely used regional/multiscale photochemical models, namely, CMAQ (Byun, 1999) and CAMx (ENVIRON, 2002), in predicting ozone concentration by comparing model outcomes with both surface measurement data from USEPA’s Aerometric Information Retrieval System (AIRS) and upper air aircraft data available from the NE-OPS study (Doddridge, 2000). The simulations for this study were carried out for the July 11, 1999 00 UTC to July 25, 1999 12 UTC period. Three levels of nested grids were used with grid resolutions of 36km, 12km and 4km (see Figure 1). The 36km grid encompasses the Eastern United States while the 4km grid encampasses the Philadelphia New Jersey region. In the vertical direction, the CMAQ application used a non-hydrostatic coordinate with 14 layers centered at 0.9975, 0.9925, 0.985, 0.9725, 0.955, 0.9325, 0.9, 0.84, 0.75, 0.65, 0.525, 0.375, 0.225 and 0.075 in sigma-p units, while the CAMx application used 8 layers corresponding to the lowest 8 layers for the CMAQ simulations. * Corresponding author address: Panos G. Georgopoulos, Environmental and Occupational Health Sciences Institute (EOHSI), 170 Frelinghuysen Road - Busch Campus, Piscataway, NJ 08854, Email: panosg@fidelio.rutgers.edu, Phone (732) 445-0159, fax (732) 445-0915 36 km Resolution Domain 12 km Resolution Domain 4 km Resolution Domain Figure 1. Nested air quality modeling domains with 36km, 12km and 4km horizontal grid resolutions employed in the present study. In order to obtain the meteorological inputs, simulations were performed with the Fifth Generation Pennsylvania State University/National Center for Atmospheric Research (NCAR) Mesoscale Model (MM5) (Grell, 1994) model for the nested multiscale model domain and for the duration of the modeling period. Details of the MM5 simulations can be found in Chandrasekar et al. (2002a,b, 2003). The emissions data were processed from the National Emissions Trends (NET) (USEPA, 1999) inventory using MCNC's Sparse Matrix Operator Kernel Emissions (SMOKE) (Houyoux, 1999) modeling system. The ozone concentration data from AIRS and from the monitor station at Philadelphia Air Management Services Laboratory, made available through the NE-OPS study, were used for comparisons with the model predicted ozone values. The upper air ozone data used for comparison with model prediction were taken from the University of Maryland instrumented flights with Cessna and Aztec aircrafts (Doddridge, 2000). Both CMAQ and CAMx simulations were performed for the three levels of nested grids. Figure 3 shows the daily maxima of ground level ozone spatial distributions for 7/17/1999, as predicted by CMAQ and CAMx, respectively, over the 4km resolution domain; one can see that CAMx predicts higher peaks while CMAQ predicts wider extent of ozone. Figure 4 presents space-time paired plots and quantilequantile plots for ground level ozone concentrations observed at fourteen AIRS ozone monitor stations in New Jersey and one NEOPS station at Philadelphia during July 11-25, 1999, versus model predictions by CMAQ and CAMx, respectively, at the locations of those monitor stations, at the hours when those monitor data were collected. One can see that for the middle range of concentrations the two models calculate similar concentration values but for the lower concentration range the CMAQ predictions tend to be higher than those of CAMx while for the high concentration range CAMx tends to overpredict ozone values. 3. RESULTS Figure 2. Air quality monitoring stations and flight tracks in the vicinity of NE-OPS. The circles indicated in the figure correspond to a radius of 50 Km and 100 Km with the Baxter NEOPS site at the center. Figure 2 shows the air quality monitoring stations and flight tracks in the vicinity of NEOPS Baxter site. Also depicted in the same figure (in purple) is the area representing urban Philadelphia, the region representing the focus of a population exposure study to Ozone and fine Particulate Matter during the summer period of 1999 (Georgopoulos et al., 2003). Figure 3. Daily maxima of ground level ozone spatial distributions for 7/17/1999 predicted by CMAQ (upper) and CAMx (lower) for the 4km resolution grid. Figure 6 shows comparisons of upper air predictions of ozone concentrations from both CMAQ and CAMx with aircraft data collected during the NE-OPS study on a flight on July 18, 1999. One can see for the July 18 evening flight, that both model predictions agree with the measurement data for altitudes in the range of 200-600 m, and both under-predict, to a different degree, for altitudes higher than 700m and also at the surface. Figure 5 shows comparisons of 4km resolution CMAQ and CAMx ozone time series predictions with observed data from monitors located in Middlesex, NJ and Philadelphia, PA. The observation data for Philadelphia were obtained from the NE-OPS study, while those for NJ are from USEPA's AIRS database. One can see an over-prediction of ozone by CAMx on certain high ozone days for Middlesex. 40 0 40 80 120 Observed Concentrations (ppb) 120 80 40 0 160 0 40 80 120 Observed Concentrations (ppb) 160 CAMx−4km Predicted Concentrations (ppb) 80 CMAQ−4km Predicted Concentrations (ppb) 120 0 160 160 CAMx−4km Predicted Concentrations (ppb) CMAQ−4km Predicted Concentrations (ppb) 160 120 80 40 0 160 0 40 80 120 Observed Concentrations (ppb) 120 80 40 0 160 0 40 80 120 Observed Concentrations (ppb) 160 Figure 4. Space-time paired comparisons and quantile-quantile plots of ground level ozone concentrations during July 11-25, 1999 over the 4 km resolution domain: the observation data were measured at 14 AIRS stations located in New Jersey plus the NE-OPS station located in Philadelphia: (a) observed versus CMAQ predicted, space-time pairs; (b) observed versus CAMx predicted, space-time pairs; (c) observed versus CMAQ predicted, quantile-quantile; (d) observed versus CAMx predicted, quantile-quantile. PHILADELPHIA, PENNSYLVANIA, Monitor ID: Baxter Phil-AMS ELM Ozone Concentration (ppb) Ozone Concentration (ppb) MIDDLESEX, NEW JERSEY, Monitor ID: 340230011442011 180 monitor 160 CMAQ-cb4-4km 140 CAMx-chem3-4km 120 100 80 60 40 20 0 07/11/99 07/13/99 07/15/99 07/17/99 07/19/99 07/21/99 07/23/99 07/25/99 180 monitor 160 CMAQ-cb4-4km 140 CAMx-chem3-4km 120 100 80 60 40 20 0 07/11/99 07/13/99 07/15/99 07/17/99 time (EDT) 07/19/99 07/21/99 07/23/99 07/25/99 time (EDT) Figure 5. Ozone time series comparisons between CMAQ and CAMx 4km resolution model predictions and observation data for Middlesex, NJ and Philadelphia, PA. The observation data for Philadelphia were obtained from the NE-OPS study, while those for Middlesex, NJ are from USEPA's AIRS database. 19a spiral up O3 7/18/1999 20:46-22:36 EDT Aircraft CAMx-4km CMAQ-CB4-4km 1400 1200 1200 1000 1000 Height (m) Height (m) 19a spiral down O3 7/18/1999 20:46-22:36 EDT Aircraft CAMx-4km CMAQ-CB4-4km 1400 800 600 400 400 200 200 0 4. CONCLUSIONS 800 600 0 0 50 100 150 O3 Concentration (ppb) 200 measurements on 7/18/1999 20:46-22:36 EDT. (left panel: spiral up; right panel: spiral down) 0 50 100 150 O3 Concentration (ppb) 200 Figure 6. Comparison of 4 km resolution CMAQ and CAMx ozone predictions with flight The comparisons of CMAQ and CAMx model predictions with surface measurement data from AIRS and NE-OPS show relatively reasonable agreements for ozone predictions. The model predictions capture the general trends of change in the time series plots. Considerable discrepancies can be seen from the comparison of upper air model predictions and aircraft measurement data. It is therefore necessary to further examine the options and assumptions underlying the application of these models in order to identify the causes of this discrepancy; though it may be reasonable to assume that the use of a higher number of layers in the CMAQ application (fourteen layers) versus that in the CAMx application (eight layers), which was made to reflect typical practice in the application of the two models, explains the better agreement of CMAQ results with upper air observation, further investigation of this issue is necessary. Atlantic region. In Proceedings of the PM2000: Particulate Matter and Health Conference, Charleston, SC, January 25-28, 2000; A&WMA, 2000; pp 4-5. ENVIRON, 2002: User’s Guide, Comprehensive Air Quality Model with Extensions (CAMx), version 3.10; http://www.camx.com/pdf/CAMx3.UsersGuide.020 410.pdf. ACKNOWLEDGMENTS Support for this work was provided by the State of New Jersey Department of Environmental Protection (NJDEP) funded Ozone Research Center (ORC); the U.S. EPA Center for Exposure and Risk Modeling (CERM) (EPAR-827033); and the U.S. EPA funded NorthEast Oxidant and Particle Study (NE-OPS) (EPA-TPSU-UMDNJ826373-14). Appreciation is extended to all the members of the NE-OPS team for their contributions to the work presented here. Fast, J.D.; Zaveri, R.A.; Bian, X.; Chapman, E.G.; Easter, R.C., 2002: Effect of Regional-scale Transport on Oxidants in the Vicinity of Philadelphia during the 1999 NE-OPS Field Campaign; J. Geo. Res. 2002, Vol 107, No. D16. Georgopoulos, P.G.; Wang, S.W.; Vyas, V.M.; Sun, Q.; Burke, J.; Vedantham, R.; McCurdy, T.; Özkaynak, H., 2003: A Source-to-Dose Assessment of Population Exposures to Fine PM and Ozone in Philadelphia, submitted to Journal of Exposure Analysis & Environmental Epidemiology. REFERENCES Byun, D. W., 1999: Ching, J. K. S. Science Algorithms of the EPA Models-3 Community Multiscale Air Quality (CMAQ) Modeling System; EPA/600/R-99/030; USEPA Report. Chandrasekar, A.; Doddridge, B.; Philbrick, C.R.; Clark, R.; Georgopoulos, P.G., 2002a: A Comparative Study of Prognostic MM5 Meteorological Model with Aircraft, Wind Profiler, Lidar, Tethered balloon and RASS data over Philadelphia during a 1999 Summer Episode, Journal of Environmental Fluid Dynamics, accepted for publication. Chandrasekar, A.; Doddridge, B.; Philbrick, C. R.; Clark, R.; Georgopoulos, P. G., 2002b: An evaluation study of RAMS simulations with Aircraft, Wind Profiler, Lidar, Tethered balloon and RASS data over Philadelphia during a 1999 Summer Episode, submitted to Environmental Fluid Mechanics, accepted for publication. Chandrasekar, A.; Philbrick, C. R.; Doddridge, B.; Clark, R.; Georgopoulos, P. G., 2003: Evaluating the performance of a computationally efficient MM5/CALMET system for developing meteorological inputs to air quality models, Atmospheric Environment 37(23): 3267-3276. Doddridge, B.G., 2000: An airborne study of chemistry and fine particles over the U.S. Mid- Grell, G.A.; Dudhia, J.; Stauffer, D.R., 1994: A description of the Fifth-Generation Penn State NCAR Mesoscale Model (MM5); NCAR TN-398; NCAR Technical Note; National Center for Atmospheric Research, Boulder, Colorado; 138 pp. Houyoux, M. R; Vukovich, J.M., 1999: Updates to the Sparse Matrix Operator Kernel Emissions (SMOKE) Modeling System and Integration with Models-3. Presented at The Emission Inventory: Regional Strategies for the Future, 26-28 October, Raleigh, NC, Air & Waste Management Association. Philbrick, C.R.; Clark, R.D.; Koutrakis, P.; Munger, J.W.; Doddridge, B.G.; Miller, W.C.; Rao, S.T.; Georgopoulos, P.; Newman, L., 2000: Investigations of Ozone and Particulate Matter Air Pollution in the Northeast. In Proceedings of the PM2000: Particulate Matter and Health Conference, Charleston, SC, January 25-28, 2000; A&WMA, pp 1-3. United States Environmental Protection Agency, National Emissions Trends (NET), 1999: ftp://ftp.epa.gov/EmisInventory