DIURNAL VARIATION OF SUMMER RAINFALL OVER EAST CHINA, KOREA AND JAPAN

Abstract

Over east China, Korea and Japan, diurnal variation of rainfall during the summer months of May to August is analyzed. This region is dominated by the monsoon and is found to have a morning maximum with, if the location is favorable, an afternoon maximum as well. The limited vertical extent of the monsoon circulation, as well as lack of turbulence, favors the advection of warm air at low levels between midnight and sunrise. This causes wide-spread over-turning; convective clouds develop, radiation from the tops assists the process, and a morning rainfall-maximum results. This usually occurs at or before dawn inland and in temperate coastal regions, but somewhat after dawn in tropical or subtropical coastal regions. The afternoon maximum is due to convection produced by surface heating. Surrounding regions show no such marked pattern.