92nd American Meteorological Society Annual Meeting (January 22-26, 2012)

Wednesday, 25 January 2012
Investigation of Aerosol Indirect Effects on Simulated Heavy Rainfall Over the Korean Peninsula
Room 244 (New Orleans Convention Center )
Kyo-Sun Sunny Lim, Yonsei University, Seoul, South Korea; and S. Y. Hong

Aerosols indirect effects on simulated moist convections have been investigated with new parameterization methods related to cloud and precipitation processes in a model. For the purpose, a new double-moment bulk-cloud microphysics scheme, the Weather Research and Forecasting (WRF) Double-Moment 6-class (WDM6) Microphysics scheme which is based on the WRF Single-Moment 6-class (WSM6) Microphysics scheme, has been developed. The number concentrations for cloud, rain waters, and cloud condensation nuclei (CCN) number concentration are also predicted in the WDM6 scheme, together with the prediction for the mixing ratios of water species. In addition, the simplified Arakawa-Schubert (SAS) cumulus scheme has been modified to include the microphysical effects of aerosols in moist convection processes. Three parameters for conversion, re-evaporation, and downdraft efficiency, which are related to the microphysics processes in a cumulus parameterization scheme, were devised to include the aerosol effects, based on the results from the cloud resolving simulation. A 3D-moist real convection system was tested to investigate the aerosol effects on storm development and surface precipitation. The impact of the aerosol concentration on the simulated storm was evaluated by varying the initial CCN number concentration in the WDM6 microphysics scheme. Total surface precipitation increases in dirty environment on a cloud resolving testbed. In addition, humidity changes the precipitation response under the varying CCN number concentrations. The surface precipitation response with varying CCN number concentrations under a coarse resolution configuration with the modified SAS scheme, are well matched with the high-resolution (cloud resolving) simulation in which only cloud microphysics scheme is used for the cloud-precipitation processes. This assures us that the modified SAS scheme reasonably includes the microphysical effects of aerosols on precipitation formation.

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