Numerical simulation of vertical microphysical structure of a cold front precipitation cloud system

The mesoscale model WRF has been used to simulate the evolution of a cold front precipitation cloud system on 4-5 October 2008 in Shijiazhuang region, China. The characteristics of cloud development, precipitation, cloud microphysical structure and cloud microphysical process are investigated. Results show that the distribution of cold front precipitation was nonhomogeneous with some precipitation significance regions, and the cloud microphysical structure was nonhomogeneous in space, but vertical distributions of ice crystal, snow, graupel, cloud water and rain water had good agreements with the distribution of cloud system. The main microphysical mechanism of precipitation was that ice crystals became larger by accretion of supercooled water in fallen process and continued growing through the warm-layer. Both mechanisms of precipitation of cold-cloud and warm-cloud were verified to exist in the cloud system, and the start of precipitation depend largely on the former one. Both the middle-layer and upper-layer of the cloud system were cold-cloud structure while the lower-layer was warm-cloud structure, therefore, this configuration was beneficial to the occurrence of seeding-feeding precipitation mechanism.