The impact of the Western Ghats on lightning activity on the western coast of India

• Development of a zone of high lightning activity parallel to the Western Ghats.
• Lightning activity undergoes a bi-annual variation over sea and land areas.
• Lightning activity is enhanced by 38% during the 1998–2012 period.

The effect of the Western Ghats on the lightning activity across the west coast of India around the coastal metropolitan city of Mumbai during the 1998–2012 period is investigated using data from the Lightning Imaging Sensor (LIS) onboard the Tropical Rainfall Measuring Mission (TRMM) satellite. A land–sea contrast of an order of magnitude in the lightning activity is observed even in a small area across the western coast of India. The shape of a zone of high lightning activity formed almost parallel to the Western Ghats during the onset and withdrawal phases of monsoon, strongly suggests the effect of the Western Ghats in its formation. Seasonal variation of the lightning activity in this area and also in each of its four equal sectors (two each over the Arabian Sea and over land) is bi-annual with one peak each in the onset (May/June) and withdrawal months (September/October) of monsoon and a sharp dip to very low values during the monsoon months (July/August) of maximum seasonal rainfall. The lightning activity in each sector is found to increase over the 1998–2012 period. However, the increase in lightning activity over the sector containing Mumbai is found to be greater during the pre- and post-monsoon periods and smaller during the monsoon period as compared to an identical sector immediately south of it.