Synergy between INSAT-3D infra-red and GPM microwave radiometer for precipitation studies

Abstract

The Indian National Satellite System (INSAT) based Multispectral Rainfall Algorithm (IMSRA) operationally provides precipitation estimates using measurements provided by the Kalpana satellite from 2008 onwards and the INSAT-3D from 2014 onwards over Indian land and oceanic regions for dissemination to the users. Here, an attempt is made to estimate rainfall over the Indian monsoon region by the synergistic use of geostationary INSAT-3D IMSRA derived rainfall estimates and rain data from the Global Precipitation Measurement (GPM) Microwave Imager (GMI) using a suitable objective analysis method. The objective criteria of a successive correction method benefit from high spatial and temporal resolutions of the geostationary satellite and infrequent but more accurate microwave-based rainfall estimates, particularly during heavy rain conditions. The method is applied to various case studies for the southwest monsoon season of 2015 at both instantaneous and daily scale. A comparison is made with ground data and also with independent global concurrent rainfall products. The merged rainfall estimates shows noticeable improvement over the Infrared (IR)-based rainfall estimates over various parts of the Indian land and oceanic regions on a daily scale. Overall, results reveal that the GMI type radiometer in low inclination orbit like the Megha-Tropiques and Tropical Rainfall Measurement Mission (TRMM) could be more useful for synergistic use with INSAT-3D. It has the potential to predict more accurately near real-time tropical rainfall, particularly over the Indian monsoon region, which makes it a valuable source of information for flood forecasting, agriculture and water resource management, numerical weather prediction, and numerous other applications in the hydro-meteorological sciences.