Spatial and temporal variations in the frequency of thunderstorm days over India

The present study investigates the spatial and temporal variations in the frequency of thunderstorm days over India, based on data from 294 observatory stations for four overlapping 30-year time periods: 1951–1980, 1961–1990, 1971–2000 and 1981–2010. Analysis of the data revealed a significant decreasing trend in thunderstorm frequency over India. Relative to the 1951–1980 time period, there has been a net decrease of 34% in the frequency of thunderstorm days during the 1981–2010 period. Seasonal analysis confirms, unsurprisingly, that the maximum thunderstorm frequency occurs during monsoon season (June–September), with the lowest frequency occurring over the winter season (January–February). June is the month with the highest number of thunderstorm days, while December has the lowest. The greatest number of thunderstorms is observed over northeastern India, and the smallest number in the western parts of the country. Regional investigations show a wide variability in the occurrence of thunderstorms over space and time. The frequency of thunderstorm days over the mountains is much higher than over the plains at the same latitude. © 2017 Royal Meteorological Society