Spatiotemporal variability and trends of hailstorms over India

Changes in hailstorm dynamics to climate variability/change have become a topic of community interest recently. However, the lack of persistent and homogenous observations makes it difficult to confidently describe either its spatial shifts or its inter-annual variations. India, prone to hailstorms is impacted adversely, especially during pre-monsoon season (February to April). In this study, a novel attempt is made to characterize the changes in dynamics and coverage of hailstorms in India at a district scale. Region-wise, state-wise, district-wise, & month-wise distributions were analysed using the datasets from 1975 to 2020 and the hail hotspots were delineated using Kernel Density estimation. Prominently, the trend analysis was performed using the non-parametric Mann-Kendall test & Sen's slope estimator. The hail events have covered the majority of the country in the recent past (1998-2020) compared to 1975-1997 with a net increase of 307 events and maximum occurrence in the North and North-west region with a hailstorm density of 12.79%, confined to the period from January to May. Among the states, Himachal Pradesh recorded maximum hail events spread over the majority of the months despite Maharashtra (614) being the highest hailstorm-observed state of the country during the study period. Moreover, the district-level analysis revealed a considerable increasing trend in Delhi, Ranchi, Bhopal, and Raisen and decreasing trends in Mayurbhanj, Anantnag, and Jammu. However, Nagpur of Maharashtra state was the only district that recorded hailstorms in all years except 1977 and longest continuous streak of hail events for 14 days in a single month (March 1978). As far as months are concerned, March recorded the highest number of hail events (1046) followed by April (690) and February (592). It was also found that 62% of the districts in the country experienced at least one hail event and a significant positive trend in the inter-annual hailstorm events was observed with a Sen's slope of 0.43 during the past 46 years. Therefore, this study will help in prioritizing and planning hail disaster management and enhancing preparedness for post-hail interventions in the hail hot spots of India.