Seasonal transition of predominant precipitation type and lightning activity over tropical monsoon areas derived from TRMM observations

Monthly statistics from TRMM-PR and LIS observations for the three years 1998 to 2000 describe large-scale features in rainfall and lightning activity during pre-monsoon and monsoon periods of the Asian and South American summer monsoons. Heavy ( similar to 5 - 10 mm/day) pre-monsoon rainfall in the one or two months before onset was widespread mainly over land. Pre-monsoon rainfall was highly convective and characterized by active lightning, a high ratio of convective rain, and high echo tops. After onset, in contrast, intense rains also occurred over the ocean and land, however, convective intensity over land was diminished. Lightning activity was suppressed over the Amazon basin and Bangladesh during the latter half of the summer monsoon.