TRMM observed vertical structure and diurnal variation of precipitation in south Asia

This paper represents the vertical structure (using TRMM-2A25 data of 2000-2003) and diurnal variation (using TRMM-3B42RT data of 2002-2004) of precipitation from pre-monsoon to post-monsoon periods in and around Bangladesh. TRMM-2A25 data analysis reveals that pre-monsoon, monsoon and post-monsoon precipitations are strong, moderate and less intensified, respectively. Strong rain rates are found at higher altitudes for pre-monsoon and relatively at lower altitudes for later periods. Averages from 4 years data, it is found that maximum rain rate in April, July and October is 114.19, 73.88 and 49.28 mm/h, respectively. In general, pre-monsoon echoes are tall compared to monsoon and post-monsoon periods. However, the maximum echo top height of about 18.25, 18.8 and 18.25 km is found during the pre-monsoon, monsoon and post-monsoon periods, respectively. Analyzing TRMM-3B42RT data it is found that the maximum rainfall over Bangladesh and northeast of the Bay of Bengal are appeared at 06 LT (local time) during monsoon period. In the same period the maximum rainfall over India is found at 18 LT. For the entire rainy season (March-November) the maximum rainfall over Bangladesh is occurred at 06 LT with a secondary maximum peak at 15 LT. The morning maximum rainfall at 06 LT over Bangladesh is confirmed after compared with the same obtained from ground-based rain-gauge data. This analysis reveals that in Bangladesh the overestimation and underestimation of rainfall by TRMM in pre-monsoon and monsoon respectively depends on different vertical structures of precipitation fields in corresponding periods.