Relationships between Rain Characteristics and Environment. Part I: TRMM Precipitation Features and the Large-Scale Environment over the Tropical Pacific

Abstract

ifferences in the characteristics of rain systems in the eastern Pacific (EP) intertropical convergence zone (ITCZ) and the western Pacific (WP) warm pool are quantitatively examined in relation to the large-scale environment. This study mainly uses precipitation feature (PF) data observed by the precipitation radar (PR) on board the Tropical Rainfall Measuring Mission (TRMM). The PFs are classified into four types according to their areas and maximum heights. Rain from tall unorganized systems and very tall organized systems tends to be dominant in high-SST regions such as the WP. On the other hand, the EP has more rain from congestus and organized systems with moderate heights than the WP. It is shown that shallow rain from congestus and moderately deep rain from organized systems are highly correlated with shallow (1000?925 hPa) convergence fields with coefficients of 0.75 and 0.66, respectively. These relationships between characteristics of rain systems and the large-scale environment are robust through all seasons.