ATMOSPHERIC MOISTURE TRANSPORT ASSOCIATED WITH MULTI-DAY EXTREME PRECIPITATION EVENTS OVER BRAHMAPUTRA RIVER BASIN IN INDIA DURING THE INDIAN SUMMER MONSOON

Abstract

As the temperature rises due to climate change, the atmosphere becomes more capable of retaining moisture, which contributes to more frequent and intense extreme precipitation events. These precipitation extremes, which take place over several consecutive days i.e. multi-day, are one of the leading causes of floods. In recent years, there has been a substantial rise in flooding caused by extreme multi-day extreme precipitation, and this trend is expected to continue in the future. The Brahmaputra river basin has a greater risk of flooding compared to other regions in India. These major floods usually occur during summer monsoon season, which can be associated with their greater vulnerability, probability of hazard, and exposure as transboundary river basins, thus becoming a major concern. Therefore, it becomes essential to rank such extreme events based on their characteristics and comprehend the underlying atmospheric dynamics that cause them. In the first part of this study, we ranked multi-day precipitation extremes on the basis of intensity and spatial extent during the Indian summer monsoon (ISM) season over the Brahmaputra basin in India using a high-resolution daily precipitation dataset for 71 years period (1951 - 2021). To rank multi-day precipitation extremes, we computed accumulated normalized precipitation anomalies for 1-,3-,5- and 7- days. Also, spatial extent (in percentage) and the mean values of these anomalies exceeding the 95th percentile over this area are computed to rank extreme precipitation events.