Improved CAMS cloud microphysics scheme and numerical experiment coupled with WRF model

The Chinese Academy of Meteorological Sciences ( CAMS) two-moment bulk microphysics scheme was employed in this study, and a new parameterization approach to simulate the heterogeneous droplet activation was introduced into the scheme. The proposed scheme predicts both the mixing ratio and the number concentration for five hydrometeor species (cloud water, rain, cloud ice, snow, and graupel). Moreover, the improved CAMS scheme was coupled with the Weather Research and Forecasting model (WRF v3.1), which makes it possible to investigate the effects of aerosol on clouds and precipitation. The rain event occurring on 23 similar to 24 April 2009 in north China was simulated using the coupled CAMS scheme and three sophisticated microphysics schemes in the WRF model. Results showed that the new scheme performed reasonably well in describing the characteristic of precipitation and the microphysics structure of cloud. The spatial pattern of precipitation, the intensity and position of precipitation center simulated by.:he new scheme were generally in agreement with the surface observation data. The simulated cloud droplet number concentration in the new scheme was close to that in WDM6 scheme, which suggests that the involved approach of aerosol activation is basically reasonable. The simulated number concentration of other hydrometeor species in the new scheme was sometimes one order of magnitude different from that in Morrison scheme, which indicates that there is still some inherent uncertainty in simulating the hydrometeor number concentration in cloud physics research.