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Friday, August 3, 2018

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Trends in occurrence of high-intensity monsoon rainfall events during the 20th century in the Indian Himalaya
Alok Bhardwaj

Trends in occurrence of high-intensity monsoon rainfall events during the 20th century in the Indian Himalaya

Event date: 3 August 2018 - 12:00pm to 1:00pm
Event type: Seminar
Venue: ASE 3D Visualisation Laboratory (N2-B1c-16c)
Speaker: Alok Bhardwaj
About the speaker:

Dr Alok Bhardwaj is a new research fellow at the Earth Observatory of Singapore, Nanyang Technological University. His research aims to understand the science of natural hazards including extreme rainfall, landslides, and floods, using remote sensing, hydro-meteorology and field studies. He has focused his research efforts on Asia to impact better coordination and quick response to natural hazards.

He recently completed his PhD in Physical Geography from the National University of Singapore in March 2018. Prior to this, he obtained his Masters (M.Tech.) in Remote Sensing from Indian Institute of Technology, Bombay, India and Bachelors (B.Tech.) in Civil Engineering from G.B. Pant University of Agriculture and Technology, India.

High-intensity monsoon rainfall in the Indian Himalaya generates multiple environmental hazards, for example, the devastating large flash flood and many small and large landslides in the western Indian Himalaya in June 2013. This study examines the 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 Ganga Catchment in the Indian Himalaya. Using trend analysis on the Indian Meteorological Department rainfall dataset, statistically significant positive trends are found 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 north of the Main Central Thrust (MCT) in the Higher Himalayan region encompassing upstream sections of the upper Ganga Catchment. 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. Our results further indicate that the highest frequency of large-scale events in the last 113 years occurred under the negative Arctic Oscillation (AO) scenario. Also, the AO is more likely to influence the occurrence of extreme monsoon events than events of a smaller magnitude. The implications of these findings are that under the scenario of statistically significant increasing rainfall depths and frequency in the Higher Himalayan region, which is influenced by a dominant negative AO synoptic system, supports the notion of a higher frequency of rainfall-induced hazards in the future.

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