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Simulating Present-Day and Future Regional Air Quality as Climate Changes: Model Evaluation

John P. Dawson 1,2, Pavan Nandan Racherla 2, Barry H. Lynn 3,
Peter J. Adams 2,4, and Spyros N. Pandis 1,5


The Global-Regional Climate-Air Pollution modeling System (GRE-CAPS) has been developed, linking a general circulation model/chemical transport model (GCM/CTM), a regional meteorological model, and a regional chemical transport model (CTM). This modeling system has enabled the examination of the effects of changes in climate, intercontinental transport, and global and regional emissions on regional and urban air quality. The GRE-CAPS system consists of the GISS II’ GCM/CTM, the MM5 regional meteorological model, and the PMCAMx regional CTM. Global-scale meteorology and pollutant concentration fields are generated by the GCM/CTM. Meteorology is downscaled to the regional level using MM5. Intercontinental transport is imulated by using the GCM/CTM-predicted concentrations around the edge of the regional CTM domain as chemical boundary onditions in the regional CTM.

The modeling system is evaluated for the present day, with model predictions compared to measured ozone and speciated PM2.5 measurements. Model predictions for five present-day Januaries and Julys are compared to measurements from the STN and IMPROVE databases from 2001-2005. Concentrations at 23 sites spread throughout the Eastern US modeling domain were used for comparisons. GRE-CAPS performed rather well in capturing present-day pollutant concentrations. Model biases and errors were similar to those for traditional model evaluation of historical air pollution episodes.

1Department of Chemical Engineering, Carnegie Mellon University, Pittsburgh, PA
2Department of Engineering and Public Policy, Carnegie Mellon University, Pittsburgh, PA
3Department of Atmospheric Sciences, The Hebrew University of Jerusalem
4Department of Civil and Environmental Engineering, Carnegie Mellon University, 5000 Forbes
Ave., Pittsburgh, PA 15231 E-mail:
5Department of Chemical Engineering, University of Patras, Patras, Greece