Microphysical Evolution of Warm-type Heavy Rainfall from Satellite Measurements and Modeling Study

Satellite observations reveal that medium-depth heavy rain systems (i.e., warm-type heavy rainfall) are dominantly found over the area near the Korean peninsula. It is shown that moist-adiabatically near neutral conditions prevail for warm-type heavy rainfall, 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 humidity 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 are important for developing cold-type heavy rainfall. In contrast, the collision-coalescence process between liquid particles are shown to be the mechanism for increasing the radar reflectivity toward the surface in the storm core region for the warm-type heavy rainfall. In addition, the microphysical evolution of the warm-type heavy rainfall appears to be relatively insensitive to the wind shear conditions in comparison to the cold-type heavy rainfall.