A cloud-resolving modeling study of a torrential rainfall event over China

[1] A torrential rainfall event that occurred in Hunan, China in June 2004 is investigated using a two-dimensional cloud-resolving simulation. The model is integrated for 6 days with imposed zonally uniform vertical velocity, zonal wind, horizontal temperature, and vapor advection from National Centers for Environmental Prediction/National Center for Atmospheric Research reanalysis data. The comparison in surface rain rate and reflectivity between the simulations and observations shows good agreement. The simulation data during the torrential rainfall event (a 37-hour period) are further analyzed to explore the physical causes in the surface rainfall processes. The time- and domain-mean analysis shows that although their rates in the onset and mature stages are similar, vapor convergence mainly supports local vapor gain in the onset stage and surface rainfall in the mature stage. As a result, the surface rain rate is significantly smaller in the onset stage than in the mature stage. The weakening of vapor convergence finally suppresses the surface rainfall during the decay stage.