Two types of heavy rainfall over the Korean peninsula under the humid East Asian summer environment

Heavy rainfall types were objectively classified by applying K-means clustering to the vertical structure of radar reflectivities, instantaneously measured by Tropical Rainfall Measuring Mission (TRMM) Precipitation Radar (PR) over East Asia for summers of 2002-2011. First type (cold-type heavy rainfall) was characterized by high storm height and abundant ice crystals under convectively unstable conditions over the China continent. By contrast second type (warm-type heavy rainfall) was associated with relatively low storm height and less ice crystals under the humid environment and intensive moisture flux convergence along the western periphery of the North Pacific high. These two types also exhibited sharp contrasts in the seasonal change (northeastward propagation from China to Korea/Japan vs. northward propagation of Meiyu-Changma-Baiu front) and diurnal peak (late afternoon vs. early morning) of occurrence frequency. Although third type in the center of North Pacific high showed the lowest vertical extent and ice water content, its contribution to total heavy rainfall was limited to 4%. The contribution to total heavy rainfall in East Asia was most overwhelming in second type (60%). The spatio-temporal evolutions of heavy rainfall types were also investigated from the 10-yr composites of geostationary satellites and reanalysis data over the Korean peninsula. The cold-type heavy rainfall was characterized by eastward moving cloud system with oval shape concentrated on small area and short life time, whereas the warm-type heavy rainfall showed comparatively wide spatial distribution with tilted area from southwest to northeast and thus long-lived pattern. The evolution difference of cloud pattern was closely related with strong large-scale convergence for the warm-type heavy rainfall. The synoptically-driven long-lasting feature of warm-type clouds should be importantly considered in future weather forecasting because it involves flood risk in term of cumulative rainfall.