Atmospheric Chemistry and Physics Discussions www.atmos-chem-phys-discuss.net 1680-7367 1680-7375 8 4 2008 10.5194/acpd-8-14765-2008 http://www.atmos-chem-phys-discuss.net/8/14765/2008/ http://www.atmos-chem-phys-discuss.net/8/14765/2008/acpd-8-14765-2008.html http://www.atmos-chem-phys-discuss.net/8/14765/2008/acpd-8-14765-2008.pdf 14765 14817 2008-08-01 Coupling aerosol-cloud-radiative processes in the WRF-Chem model: investigating the radiative impact of elevated point sources E. G. Chapman elaine.chapman@pnl.gov W. I. Gustafson, Jr. R. C. Easter J. C. Barnard S. J. Ghan M. S. Pekour J. D. Fast Pacific Northwest National Laboratory, P.O. Box 999, Richland, Washington D.C. 99352, USA The local and regional influence of elevated point sources on summertime aerosol forcing and cloud-aerosol interactions in northeastern North America was investigated using the WRF-Chem community model. The direct effects of aerosols on incoming solar radiation were simulated using existing modules to relate aerosol sizes and chemical composition to aerosol optical properties. Indirect effects were simulated by adding a prognostic treatment of cloud droplet number and adding modules that activate aerosol particles to form cloud droplets, simulate aqueous-phase chemistry, and tie a two-moment treatment of cloud water (cloud water mass and cloud droplet number) to an existing radiation scheme. Fully interactive feedbacks thus were created within the modified model, with aerosols affecting cloud droplet number and cloud radiative properties, and clouds altering aerosol size and composition via aqueous processes, wet scavenging, and gas-phase-related photolytic processes. 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