RADIATIVE AND MICROPHYSICAL EFFECTS OF ICE CLOUDS ON A TORRENTIAL RAINFALL EVENT OVER HUNAN, CHINA

The radiative and microphysical effects of ice clouds on a torrential rainfall event over Hunan, China in June 2004 are investigated by analyzing the sensitivity of cloud-resolving model simulations. The model is initialized by zonally-uniform vertical velocity, zonal wind, horizontal temperature and vapor advection from National Centers for Environmental Prediction (NCEP) / National Center for Atmospheric Research (NCAR) reanalysis data. The exclusion of radiative effects of ice clouds increases model domain mean surface rain rates through the increase in the mean net condensation associated with the increase in the mean radiative cooling during the onset phase and the increases in the mean net condensation and the mean hydrometeor loss during the mature phase. The decrease in the mean rain rate corresponds to the decreased mean net condensation and associated mean latent heat release as the enhanced mean radiative cooling by the removal of radiative effects of ice clouds cools the mean local atmosphere during the decay phase. The removal of microphysical effects of ice clouds decreases the mean rain rates through the decrease in the mean net condensation during the onset phase, while the evolution of mean net condensation and the mean hydrometeor changes from decrease to increase during the mature phase. The reduction in the mean rain rate is primarily associated with the mean hydrometeor change in the absence of microphysical effects of ice clouds during the decay phase.