Hubei Key Laboratory for Heavy Rain Monitoring and Warning Research,Institute of Heavy Rain,China Meteorological Administration
Microphysical processes in Meiyu front rainfall have an important effect on evolution of precipitation. Based on WRF (version 3.4.1) model, one Meiyu front heavy rainfall case from 29 to 30 June is analyzed with 3 different microphysics schemes (Morrison, Thompson and MY). The main findings are as follows. (1) The general large-scale circulation of the Meiyu rainfall case could be reasonably reproduced by all the three experiments with different microphysics schemes, which was consistent with ERA5 reanalysis data. The local circulation during Meiyu front heavy rainfall was significantly influenced by microphysical processes and the differences in the local features between different experiments were evident. The local circulation and updraft in the Thompson experiment were stronger than those in the other two schemes. Precipitation in all the model output was overestimated and the hourly rain rate was always greater. The overestimation of melting of ice phase hydrometeors or accretion of cloud droplet by raindrop was one of the most important causes to the overestimation of modeled precipitation. On the whole, Morrison run performed relatively better. (2)Melting of ice phase hydrometeors and accretion of cloud droplet by rain drop were the key source terms to the growth of rain drop. And evaporation process was the most important sink term. On the whole, raindrop collecting cloud droplet contributed more than melting of ice phase hydrometeors to the growth of raindrop. However, for each scheme, differences of these microphysical process terms leaded to the difference of modeled precipitation in distribution. (3) Thompson run produced the largest amount of melting of ice phase hydrometeors and evaporation (especially in low level). At the same time, it produced the largest amount of condensation which leaded to more collection of cloud droplet by raindrop. Therefore, Thompson run produced most raindrop and rainfall. The predominant product through deposition and riming process was snow and the largest amount of snow was produced. (4) Through Bergeron process, Morrison run produced more snow than graupel (ice particles nearly could be neglected), Thompson run produced predominant snow and MY run produced more snow than ice particles (graupel nearly could be neglected). The largest amount of produced ice particles in MY run through the process leaded to more ice particles than that in other schemes. (5) Cloud droplet contributed more than raindrop in riming process. In Morrison and Thompson schemes, the amount of graupel collecting cloud droplet was larger than that through other riming processes. Other riming processes contributed the growth of graupel in different degrees in Morrison run, while other riming processes nearly could be neglected compared to graupel collecting cloud droplet. And MY run produced larger amount of snow growth by deposition. Therefore, differences of Bergeron and riming processes in all three schemes lead to the differences in ice phase hydrometeors distribution.