Numerical Study On Different Clouds And Precipitation Using WRF Model Coupled With CAMS Microphysical Scheme

In this study, numerical experiments are conducted using WRF model coupled with CAMS microphysical scheme. One case simulated is mixed stratiform-convective cloud happening in North China during Aprial18-19,2009. The other case is a extraordinary rainstorm happening in Beijing during July21-22,2012. The simulated results show that:the structure of cloud, the distribution of rainfall and radar echo are similar to the observation.In this paper, one case of mixed stratiform-convective cloud is investgated using simulated results and observation datas. The main results show that:(1) the precipitation process is cold gront mixed convective-stratiform cloud with the configuration of high-level trough, middle-level vortex and ground front.(2) Simulated echo and radar echo reveal cumulus echo distributed in the background of uniform stratiform clouds echo, the echo intensity of the convective cloud is about50dbz, we can see the columnar cumulus echo in RHI.(3) The distribution of hydrometeor is heterogeneous either horizontally or vertically. Cumulus embeded stratus has more cloud-water, graupel content and rain content, stratus has little cloud-water, graupel content and rain content, melting of graupel is main source of rain.(4) At the developing phase of cumulus, there are abundan super-cooled water in cumulus embeded stratus with strong ascending motion, so seeding in these area is better.The research results of supercooled water distribution of mixed stratiform-convective cloud and stratiform cloud show that:(1) At the developing stage of cumulus, supercooled water layer is thick, supercooled water content is abundant around-10℃; Supercooled water layer is thinner in stratiform cloud, supercooled water are mainly distributed below-5℃.(2) distribution of radar echo and supercooled water corresponding to each other in the developing stage of cumulus, in the weakened period of cumulus and stratiform cloud process, supercooled water are mainly distributed in the the front of radar echo.(3) the supercooled water content and vertical speed is positively correlated, and is negatively correlated with snow and ice content.The simulated study on a torrential rain occurring in Beijing on21July2012show that:(1) Low vortex provided lifting condition for convection development, Mesescal Convective System developed on the east side of low vortex shear line, and moved towards the northeast with the low vortex. The vortex shear line moving speed was slow, when near to Beijing, leading to convective clouds generated developed in Beijing, caused the heavy rainfall.(2) The MCS echo showed that, the southern part of cloud is narrow and the northern part of cloud is wide, echo top is high.(3)Cloud water is multi-peak distribution, negatively correlated with the content of rain, ice, snow and graupel which is bimodal distribution, respectively corresponding to the two precipitation process.(4) Ice crystals precipitation mechanism is main in the process, graupel melting is the main source of rain.