Periodic Time Variation of a Low-T_BB Cloud Area in Typhoon

Abstract

In this paper, the evolution of the cloud activities for six typhoons in 1997 is examined, utilizing T_BB (equivalent Black Body temperature) data of GMS (Geostationary Meteorological Satellite)-5 split window channels. As the result, periods of 24-hour and about 10-hour are found in the time variation of the cloud areas whose cloud top temperature is lower.
Diurnal variation is found most distinctly in the time series of the cloud area of TBB lower than -40°C, which corresponds to the one whose cloud top gets at the upper level of the troposphere. The maximum and the minimum peaks of this variation appear around at 1500 JST (Japan Standard Time) and 0800 JST. And, the maximum appears corresponding to vigorous convections at 0600-1000 JST of all the vigorous convections.
About 10-hour period time variation is found most distinctly in the time series of the cloud areas of TBB lower than -60°C, which corresponds to the one whose cloud top gets at the upper level of tropopause or over. The maximum of this variation appears corresponding to a preceding vigorous convective activity which occurs in the wide region of the typhoon a few hours before.