Trends in extreme daily precipitation indices in India

We assembled daily precipitation records, initially for 3838 stations, throughout India and ultimately identified 129 stations with reasonably complete records over the period 1910 to 2000. From these daily records, we generated annual time series of seven different indices of extreme precipitation events, including total precipitation, largest 1, 5, and 30 day totals, and the number of daily events above the amount that marks the 90th, 95th, and 97.5th percentiles of all precipitation at each station. Of the 903 different time series (seven variables for 129 stations), 114 had a significant upward trend and 61 had a significant downward trend; overall, 61% of the time series showed an upward trend. The standard regression coefficients showing the strength and sign of the trend were highly correlated across the network. They generally showed increasing values in a contiguous region extending from the northwestern Himalayas in Kashmir through most of the Deccan Plateau in the south and decreasing values in the eastern part of the Gangetic Plain and parts of Uttaranchal. Our results are in general agreement with the prediction from numerical models for an increase in extreme precipitation events in India given the ongoing build-up of greenhouse gases.