Impact of Cloud Microphysics on a Process of Warm-Sector Precipitation over Jilin, Northeast China

A warm-sector rainstorm occurring in Yongji, Jilin Province on July 13, 2017 was simulated utilizing the regional model WRF3.9, and the storm development process was reproduced, which included the stages such as the initiation of mesoscale convective cells and linear convective clusters, organized system development, and the formation of bow echos. Based on the simulation data, the characteristics cloud microphysices for the mesoscale convective systems were analyzed, and their impact on the warm-sector precipitation was discussed. The results show that the precipitation process in the Yongji occurred under favorable conditions in which multi-scale environmental structure was dominated by the northeast cold vortex. The mesoscale systems was mainly a cold cloud systems, in which there was a wide warm zone and a high location of supercooled water, with the coexistence of ice and supercooled water. The "seeding" effect of the coexisting area caused a large amount of graupel. The budget analyses of the mass- and heat-hydrometeors showed that during the triggering and organizing stage of the precipitation system showed that the main source of rainwater was the accretion growth of cloud droplets, and the main sink was the collection of raindrop by ice. During the bow-shaped echo stage, besides the accretion growth of the cloud droplets, the melting of graupel also served as the main source, while the main sinks were the evaporation of rainwater in the lower layer and the collection of rainwater by the graupel in the upper layer. The main heat source of warm-sector precipitation was the latent heat released from condensation of water vapor, and the main heat sink (cooling) was the evaporation of rain and cloud water. Furthermore, during the bow-shaped echo stage, the confluence of the inflow at the frontend with the air inflow at the backend above the cold pad on the ground brought water vapor into the upper layer. The "seeding" effect significantly increased the content of the graupel particles around the height of 8 km above the ground, which coincided with the high temperature area as generated by the releasing of a large amount of latent heat through the condensation of water vapor, causing the melting of a large amount of the graupel and resulting in a strong precipitation system.