Abstract
Diurnal variations of convective activities in the southeast Asian monsoon region are examined using hourly data about 0.1 degree in spatial resolution from Geostationary Meteorological Satellite for one year. Large diurnal variations of convective activities exist over land, particularly in coastal area of the Indochina Peninsula. The variations are stronger than those over the Gulf of Thailand and the Andaman Sea. The large diurnal variations over land should be due to the strong surface heating during daytime and the interaction between land-sea circulations and the southwest monsoon. The characteristics of the diurnal variations during the rainy season are classified into two; one is May class (May, Sep. and Oct.) and the other is July class (Jun., Jul. and Aug.). The diurnal variations are strong in both classes over the Indochina Peninsula but they are stronger in July class than in May class over the Andaman Sea and North Vietnam. Seasonal changes of the diurnal variations of convetive activities is examined over five typical grids both over land and sea. Over land, the peak of the diurnal variations is found to be around on sunset, however, there are semi-diurnal cycles over ocean and the peaks are at 5 LST and 17 LST. It is also found that the seasonal changes of the diurnal variations of convective activities correspond to those of observed precipitation.
