Trends of lightning flash density over India during different seasons

Lightning flash rate data measured by the Tropical Rainfall Measuring Mission (TRMM) for the period 1996-2013 over India are analysed to study the spatial and temporal variation of lightning over India during different seasons. The convective available potential energy (CAPE) and other thermodynamic parameters data for the same period are taken for analysis. This study confirms a systematic increase in lightning flash rate density in India during the last two decades. The annual lightning flash rate density is high along the windward side of the Himalayan foothills with two peaks, one over northwestern parts of India (>50 flashes<middle dot>km(-2)<middle dot>year(-1)) and the other over northeastern parts of India (>40 flashes<middle dot>km(-2)<middle dot>year(-1)). The pre-monsoon (March-May) (0.176 flasheskm(-2)<middle dot>year(-1)) and monsoon (June-September) (0.159 flashes<middle dot>km(-2)<middle dot>year(-1)) lightning trends are the largest contributors in explaining the annual trend of 0.099 flashes<middle dot>km(-2)<middle dot>year(-1). All seasons have shown more or less positive trends while post-monsoon (October-December) has shown a negative trend (-0.013 flashes<middle dot>km(-2)<middle dot>year(-1)). The seasonal variations show that the lightning is increasing more over northwest India during the monsoon and northeast India during the pre-monsoon. To further understand the connection between lightning and climate change, a few thermodynamic or microphysical properties are also analysed. This analysis suggests that the high CAPE values together with thermodynamics and cloud microphysical processes are necessary for organized convection and lightning over this region. Additionally, correlation analysis is adopted to identify the main influencing factors and regions contributing to lightning variability. The increase in lightning activity is found to be due to an increase in CAPE, low-level moisture content and temperature. The increase in temperature and moisture is attributed to the land use land cover (LULC) changes in India. The impact of the above proxies on lightning varies from region to region and season to season. As several regions are undergoing rapid transformation due to human activity, this study provides insights into the need to understand land use related changes to local and regional lightning activity.