Numerical Studies of Influences of Ice-Phase Change Induced Diabatic Heating on Mesoscale Convective Clouds and Precipitation over the South China Sea Monsoon Region

A cloud-resolving model (CRM) and sounding data observed in the South China Sea Monsoon Experiment (SCSMEX) from 15 May to 11 June 1998 are used in this study to explore the effects of diabiatic heating induced by the ice-phase change on mesoscale convective system (MCS), precipitation, radiation, and the large scale environment. The results show that the effects of the latent heat released by the ice-phase change on the net cloud radiation can be neglected, but the diabatic heating leads to obvious changes in heat fluxes at the ocean surface. The latent heat released during the sublimation and deposition processes has a heating effect on the large-scale environment, and the atmospheric stratification becomes more stable. As a result, latent and sensible heat fluxes at the ocean surface both decrease, convective activities become weak, and precipitation decreases by about 10.11% over the northern South China Sea (SCS). The freezing process can also result in a more stable atmosphere, which is not favorable for the development of mesoscale convective system and thereby leads to a decrease in the accumulated rainfall over the northern SCS by about 2.2%. The melting process can lead to an increase in accumulated rainfall over the northern SCS, which is mainly attributed to its cooling effect on large-scale environment below the melting level. This cooling effect produces an unstable atmosphere at the lower levels, and increases the sensible heat flux transfer from the ocean surface to the atmosphere. Precipitation increases subsequently. The melting process can increase the accumulated rainfall by about 4.1%. Therefore, the diabatic heating influences precipitation mainly by directly influences the atmospheric stability, which affects vertical transport of latent and sensible heat fluxes at the ocean surface and mesoscale convective system development. Precipitation over the northern SCS changes correspondingly.