Rainfall features over the equatorial area and their diurnal variations are studied quantitatively with space-borne precipitation radar data (PR2A25 version 5) of the Tropcial Rainfall Measuring Mission (TRMM), for the period of 1998-1999.

Spectral representation of rain features; cumulative frequency of rain profiles stratified with rain-top height, is introduced. The advantage of this method is that it explicitly maintains the information about components of rain systems. It is useful in capturing the features of rain systems, since it is expected that a certain type of rain system is represented by a certain spectral distribution. Convective and stratiform rain statistics over the ocean and over the land are compared.

The diurnal variation shows that the convective rain and the stratiform rain vary almost in phase over the ocean, with an early-morning maximum during 03-06 LT. Over the land, a distinct convective rain peak of the afternoon shower is found in 15-18 LT, without accompanying diurnal variation of the stratiform rain which has a peak in midnight (24-03LT). It is also shown that afternoon showers are frequent but not the strongest, and night-time rains are relatively stronger.