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The influence of foreign vs. North American emissions on surface ozone in the US

Reidmiller, D. R., A. M. Fiore, D. Jaffe, D. J. Bergmann, C. Cuvelier, F. J. Dentener, B. Duncan, G. Folberth, M. Gauss, S. Gong, P. Hess, J. E. Jonson, T. Keating, A. Lupu, E. Marmer, R. Park, M. G. Schultz, D. Shindell, S. Szopa, M. G. Vivanco, O. Wild, and A. Zuber (2009), The influence of foreign vs. North American emissions on surface ozone in the US, Atmos. Chem. Phys., 9, 5027-5042, doi:10.5194/acp-9-5027-2009.

As part of the Hemispheric Transport of Air Pollution (HTAP; www.htap.org) project, we analyze results from 15 global and 1 hemispheric chemical transport models and compare these to Clean Air Status and Trends Network (CASTNet) observations in the United States (US) for 2001. Using the policy-relevant maximum daily 8-h average ozone (MDA8 O3 ) statistic, the multi-model ensemble represents the observations well (mean r 2 =0.57, ensemble bias = +4.1 ppbv for all US regions and all seasons) despite a wide range in the individual model results. Correlations are strongest in the northeastern US during spring and fall (r 2 =0.68); and weakest in the midwestern US in summer (r 2 =0.46). However, large positive mean biases exist during summer for all eastern US regions, ranging from 10– 20 ppbv, and a smaller negative bias is present in the western US during spring (∼3 ppbv). In nearly all other regions and seasons, the biases of the model ensemble simulations are ≤5 ppbv. Sensitivity simulations in which anthropogenic O3 precursor emissions (NOx + NMVOC + CO + aerosols) were decreased by 20% in four source regions: East Asia (EA), South Asia (SA), Europe (EU) and North America (NA) show that the greatest response of MDA8 O3 to the summed foreign emissions reductions occurs during spring in the

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Atmospheric Composition Modeling and Analysis Program (ACMAP)
Modeling Analysis and Prediction Program (MAP)