Spatial Distribution of Extreme Rainfall Events During 2017 Southwest Monsoon over Indian Subcontinent

摘要

The extreme rainfall events over India during 2017 southwest monsoon and associated mechanisms are investigated using daily rainfall, winds and SST data sets. Extreme events occurred over mainly four locations according to the designed criteria, which are westcentral India (WC), central India (CI), northeast (NE) India and northwest coastal region (NWC). The events are identified mostly in the active phase of monsoon except in the northeast India, there the extremes are during break monsoon situation. As observed over the northwest coastal region and central India, most of the rainfall events are clustered during the peak monsoon (in the month of July). The seasonal frequencies of extreme events are significantly high in the west central and central India region. On the other hand, the relative contributions of these events are exceptionally high. In the northeast India, extreme events are followed the criterion of low-level wind regimes, where westerly regime induces a positive feed-back to enhance the extreme event. The temporal distribution and relative contribution of rainfall towards seasonal total in the northeast and northwest regions differ from other two selected regions. Global circulation pattern and local updraft contribute largely towards the seasonal rainfall in the west central and central India. A positive Indian Ocean Dipole mode together with the presence of a weak La Nina eventually favoured the rainfall in the northern parts during the month of July.