Space time variation of lightning activity over Bangladesh

Lightning flash rate activity in Bangladesh is investigated using observations from the Lightning Imaging Sensor (LIS) on the NASA TRMM satellite (0.5o0.5o) data for a 10-year period (1998-2007). Results of the analysis show maximum lightning flash rate density (70 fl km-2 yr-1) over the western region of the eastern region of Bangladesh. This is attributed to the topography and the geography of Bangladesh along with the moisture availability over the region. The precipitable water content in the northern Bay of Bengal is high, and the intensity and location of the anticyclone contributes significantly to the incursion of moisture into different parts of Bangladesh. The annual variation of lightning flash rate count over the Bangladesh exhibits two peaks– one prominent peak in May and the other smaller peak in September. The height of Lifting Condensation Level (LCL) and Convective Available Potential Energy (CAPE) is almost 3-4 times smaller in the monsoon season compared to premonsoon. It is clear from the figure that the cloud-base height and CAPE in the premonsoon months i.e. March, April and May is about 3 to 4 times higher than in monsoon months i.e., June-August. Therefore both these conditions, i.e. lower cloud base height and low cloud condensation nuclei (CCN) concentration, may be the main causes for having maximum / minimum activity during pre-monsoon and monsoon season.