Quantifying Multi-Day Precipitation Extremes and Their Linkages With Atmospheric Moisture Flux Over India

The Indian subcontinent is dominated by a very pronounced summer monsoon season from June to September and a less intense autumn monsoon, both posing major challenges to the densely populated regions, namely through flash floods and landslides. Moreover, the spatial patterns and temporal extent of extreme precipitation events are not uniform across India, with event's durations varying across regions and multiple triggering factors. Here, we make use of a high-resolution daily precipitation dataset covering the entire Indian territory, from 1951 to 2022, to analyse multi-day precipitation extremes and their linkages with regional atmospheric moisture fluxes. We consider 10 sub-regions of India, characterised by different climatic regimes and apply an objective ranking of extreme precipitation events, across various time scales, ranging from 1 to 10 days. Obtained results confirm that the method accurately detects and ranks the most extreme precipitation events in each region, providing information on the daily evolution of the magnitude (and spatial extent affected) of high precipitation values in each region. Moreover, results show that top rank events can be associated with different types of storms affecting the four main coastal regions of India. In particular, some top rank events can be critically linked to long duration events (e.g., 10 days) that can be missed in ranks for shorter duration (e.g., 1-3 days) periods, thus stressing the need to employ multi-day precipitation extremes ranking. Finally, an in-depth analysis of the large-scale atmospheric circulation and moisture transport is presented for the top 10-day events influencing the four coastal regions of India. Results show low pressure systems, which persist over multiple days and play a critical role in linking IVT to MDPEs across the Indian subcontinent. Overall, we are confident that our findings are valuable in advancing disaster risk reduction strategies, optimising water resource management practices, and formulating climate change adaptation strategies specifically tailored for the Indian subcontinent.