Diurnal Variation of Summer Rainfall over Taiwan and Its Detection Using TRMM Observations

Abstract

A surface-based rainfall monitoring network reveals that summer rainfall over Taiwan exhibits a prominent diurnal variation. In this study, an attempt has been made to detect the diurnal variability of Taiwan rainfall using observations from the Tropical Rainfall Measuring Mission (TRMM) satellite. The results show that the diurnal patterns of Taiwan rainfall can be detected with TRMM Microwave Imager (TMI) observations using a satellite observation period of 36 or more days, and detected signals match reasonably with those using continuous surface observations. However, sometimes, because of the unfavorable combination of satellite sampling and the occurrence of some transient regimes in local rainfall, there is a possibility of misinterpreting the diurnal cycle. The TRMM precipitation radar sensor also reveals a diurnal cycle of convective and stratiform rainfall. The convective activity increases during the late afternoon over Taiwan, which may be the effect of convection forced by localized mass convergence caused by the sea breeze. It is of interest that TMI data indicate a significant increase of rainfall over orographic regions during the same time.