1.Key Laboratory for Cloud Physics of China Meteorological Administration,Chinese Academy of Meteorological Sciences;2.Ningxia Key Laboratory of Meteorological Disaster Prevention and Reduction
Liupan Mountain area is water conservation forest base in the northwestern of China, but the drought and lack of rain restricted the agricultural and economic development of this region. Using the Weather Research and Forecasting (WRF) model, a precipitation process occurred in Liupan Mountain area in southern Ningxia on August 21, 2018 was simulated as the basis of further research on artificial precipitation enhancement technology in this area. Based on observational data, the favorable circulation situation was analyzed, the microphysical structure and precipitation formation mechanism in the precipitation cloud system were discussed. The results show that the weather system of this precipitation process developed in the dynamic field of aloft trough associated with low vortex, and the low vortex was at the slower moving compared with the aloft trough because of the blocking effect of the Liupan Mountain terrain. The vertical structure of cloud showed a remarkable “seeding-feeding” stratified structure，but the vertical microstructure was different in different parts of the cloud system，resulting in the difference of contribution of cold and warm cloud processes to precipitation. Besides, the precipitation on the east windward side of Liupan Mountain was stronger than that in the west. Rain water was produced mainly by melting of graupel and collection of cloud water by rain. The accretion of supercooled rain was the main process of graupel growth. Layer of cloud water on the windward slope was deep with high water content. It promoted the process of accretion of rain by graupel in the supercooled layer, and provided abundant cloud water for the process of coalescence growth of raindrops, which enhanced both cold and warm cloud precipitation process. The terrain had an impact on the development of clouds and the formation of precipitation, where the cloud water decreased the warm cloud process weakened with the terrain height lowering, which also affected the growth process of the graupel.