Influence of Air Temperature on Local Precipitation Extremes Across India

In the present study, the influence of maximum temperature on rainfall events at the daily scale is explored at four locations—Chennai, Kolkata, Mumbai and New Delhi, which represent different climatic regions across India. The widely accepted binning technique is used to pair the daily temperature and rainfall (95th and 50th percentile). Two different data products—global gridded data (1979–2017) and station-based global dataset (1991–2017) are used and the scaling relationships are compared alongside the Clausius-Clapeyron scaling of 6.8% K−1. Results indicate negative scaling, ranging from −0.4 to 22% per degree Celsius (for 95th percentile rainfall) and −3 to −41% per degree Celsius (for 50th percentile rainfall) at all studied locations. It is also noticed that rainy days (> 0.3 mm rainfall) are mostly observed when temperature is above 30 °C in Kolkata and New Delhi, but in Chennai and Mumbai, rainy days are fairly common even when the temperature is below 30 °C. The evolution of the scaling relationship is studied considering four sequential time periods: 1979–1988, 1989–1998, 1999–2008 and 2009–2017. All the locations indicate negative scaling for all decades except New Delhi which indicates a very mild positive scaling during 1979–1988. Moreover, the relationship of daily rainfall with preceding days’ maximum temperature is also studied for Kolkata and Chennai, with the former showing positive scaling at three-day lag and beyond.