Trends and Variability in Extreme Precipitation over India

The frequency, intensity and duration of weather and climate extremes have increased globally over the past several decades, and the trend is projected to continue. It is important to understand the changing nature of these extremes as it contributes to better monitoring and prediction, thereby reducing the risk to society. Changes in climate and associated weather extremes may be caused both by natural factors such as internal variability, volcanic eruptions, and solar variability as well as anthropogenic factors such as GHGs, aerosols and land use changes. It is essential to differentiate between the contributions of these drivers in order to take suitable measures to mitigate and adapt. Though the changes in temperature extremes are well-documented, rainfall extremes are significantly heterogeneous around the world.

This study analyses extreme precipitation indices over India (developed by the Expert Team on Climate Change Detection and Indices; ETCCDI) and their relationship with different modes of climate variability. The study examines the mean climatology, long-term trends and variability in extreme precipitation indices over India using the daily gridded rainfall data from the India Meteorological Department (IMD). The analysis is carried out over different homogeneous zones as well as custom-defined areas over India in different seasons. The study finds significant variability of extreme indices in the 2 to 4 year time scales and highlights the role of Indian Ocean Dipole (IOD) and El Niño-Southern Oscillation (ENSO) in modulating extreme precipitation.