资源环境科技发展态势分析平台

In this study, we provide a comprehensive analysis of spatio-temporal distribution of extreme rainfall of different intensities (heavy, very heavy and extremely heavy) as well as wet spell over the Indian landmass during monsoon (June-August) of 2016-2018 through satellite observations. Moreover, there were similar to 35 extreme rainfall events during the study period, which has accumulated rainfall > 120 mm hr(-1) and the first 12 events were identified (having highest amount of accumulated rainfall in a day out of 35 events) for our study. The event locations were so selected where there is not any point observations [automatic weather station (AWS) or automatic rain gauge (ARG)] at the site of extreme rainfall events, not even within 50 km radius of the event site or if any AWS/ARG site is present but were unrecorded or unreported during the time of extreme rainfall event 70% of the extreme rainfall events (convective storms) occurred in the afternoon where 75% of the events indicates > 150 mm hr(-1) accumulated rainfall and the rest 25% shows the accumulation rate to be > 120 mm hr(-1). The factors influencing the extreme rainfall events to occur are obtained to be increased instability parameters (convective available potential energy, K-Index, Total Total's index), meteorological, thermodynamic and dynamical parameters (upper and lower level temperature gradient difference, vertical difference of equivalent potential temperature at 850 and 500 hPa, moisture flux convergence) and decreased temperature saturation deficit. The convective growth started initiating 6-7 h before the occurrence of extreme rainfall, indicating the favourable condition for severe convection. Furthermore, if the diurnal relative humidity range is maximum and there is a sharp increase in specific humidity at a location, there is a maximum probability of extreme rainfall after 5-6 h at that location. Both the Global Forecast System (GFS) and NCMRWF Unified Model (NCUM) captured the extreme rainfall events well for the year 2018 over the Indian region.