Idealized numerical experiments on the microphysical evolution of warm-type heavy rainfall

Abstract

Recent satellite observations suggested that medium-depth heavy rain systems (i. e., warm-type heavy rainfall) were predominantly found in the Korean peninsula under moist-adiabatically near neutral conditions in contrast to the traditional view that deep convection induced by convective instability produced heavy rainfall (i. e., cold-type heavy rainfall). In order to examine whether a numerical model could explain the microphysical evolution of the warm-type as well as cold-type heavy rainfall, numerical experiments were implemented with idealized thermodynamic conditions. Under the prescribed humid and weakly unstable conditions, the warm-type experiments resulted in a lower storm height, earlier onset of precipitation, and heavier precipitation than was found for the cold-type experiments. The growth of ice particles and their melting process were important for developing cold-type heavy rainfall. In contrast, the collision and coalescence processes between liquid particles were shown to be the mechanism for increasing the radar reflectivity toward the surface in the storm core region for the warm-type heavy rainfall.