Observed rainfall events and outgoing longwave radiation over contrasting river basins in Bihar, India

The long term extreme rainfall event analysis at the catchment scale is crucial for mitigation and prevention of flood like situations and water resource management. This study evaluates the different rainfall events categorized by the India Meteorological Department (IMD) over the lower Kosi and Punpun river basin using the gridded rainfall data of 0.25 degrees x 0.25 degrees resolution for the period of 1979-2018. Further, the linkage between Outgoing Longwave Radiation (OLR) and rainfall events is examined. The daily accumulated rainfall shows large variation over the Kosi river basin in compare to the Punpun basin. The number of days of moderate and heavy rainfall over the lower Kosi River has significantly decreased. In addition, light and moderate rainfall over Punpun River has also decreased; however, it is nonsignificant. No significant trend in very heavy rainfall is found for both the river basin. It is observed that the number of days in moderate rainfall events shows an acceptable negative correlation with Outgoing Longwave Radiation (OLR) over basins. This study will be helpful for the mitigation and prevention of disasters and sustainable water resource management under changing climate.