Cloud-to-Ground Lightning over the Indian Subcontinent

We examined the annual and diurnal variations of cloud-to-ground lightning over the Indian Subcontinent using data from the Global Lightning Dataset GLD360. GLD360, at present, does not classify lightning by its type (cloud and cloud-to-ground), so we applied a simple classification rule based on network-estimated peak current. Only negative and positive lightning events with estimated peak currents greater than 5 kA and 15 kA, respectively, were considered. We used five years (2011–2016) of data reprocessed using the latest geolocation algorithm and the dataset consisted of several hundred million strokes. Such a detailed representation of lightning that occurs in this region is expected to be a valuable resource for addressing the large loss of life and impact on socio-economic activity due to lightning.

Generally speaking, the lightning stroke density (strokes/sq. km/ year) map indicates a tendency for lightning to occur over land, even though relatively high lightning densities are seen over the Bay of Bengal. The largest maxima are over eastern India and Bangladesh, northwest India and northern Pakistan, the southwestern coastline of India, and southwestern Sri Lanka. There is a sharp northern boundary created by the east-west Himalayas, which separate regions with moderate-to-high lightning densities to the south of the mountain range from those with very small lightning densities to the north.

We will examine the seasonal variability of lightning density in this region. The seasons are often identified as winter (January and February), pre-monsoon or summer (March, April, and May), southwest or summer monsoon (June to September), and post-monsoon or northeast monsoon (October, November and December). Lightning is most frequent during the monsoon, and the effect of migration of the monsoon to the north from the south will be considered in ten-day increments. Further, we will consider the diurnal variation in lightning in order to identify locations where thunderstorm activity are a frequent threat to socio-economic activity.