High-intensity monsoon rainfall variability and its attributes: a case study for Upper Ganges Catchment in the Indian Himalaya during 1901–2013

High-intensity monsoon rainfall in the Indian Himalaya generates multiple environmental hazards. This study examines the variability in long-term trends (1901–2013) in the intensity and frequency of high-intensity monsoon rainfall events of varying depths (high, very high and extreme) in the Upper Ganges Catchment in the Indian Himalaya. Using trend analysis on the Indian Meteorological Department (IMD) rainfall dataset, we find statistically significant positive trends in all categories of monsoon rainfall intensity and frequency over the 113-year period. The majority of the trends for both intensity and frequency are spatially located in the Higher Himalayan region encompassing upstream sections of the Mandakini, Alaknanda and Bhagirathi River systems. The extreme rainfall trends for both intensity and frequency are found to be only located in the vicinity of the upstream section of the Mandakini Catchment. Further, we explored the relationship between the Arctic Oscillation (AO) climate system and the frequency of occurrence of high-intensity rainfall events. Results indicate that AO is more likely to influence the occurrence of extreme monsoon events when it has a higher magnitude of negative AO phase. This study will help in better understanding of the influence of climate change at higher latitudes on mid-latitude rainfall extremes, particularly in the Himalayas. The implications of the findings are that statistically significant increasing rainfall depths and frequency in the Higher Himalayan region support the notion of higher frequency of rainfall-induced hazards in the future.