The TRMM satellite carried the first space-borne active microwave radar, the Ku-band (13.8 GHz) Precipitation Radar (PR), to provide a three-dimensional structure of the tropical precipitation. Following the launch of the Tropical Rainfall Measuring Mission (TRMM) satellite in November 1997, satellite-based precipitation estimation techniques received an unprecedented boost. Precipitation is one of the key components of the global water and energy cycles, and a robust constellation of precipitation-related satellite sensors could provide reliable global distributions of precipitation at distinct spatiotemporal scales. The results of this study would be beneficial for end-users to integrate this multi-satellite product in any specific application. Furthermore, results reveal that IMERG estimates under-detect and overestimate light rainfall intensity of 2.5–7.5 mm day −1, which needs to be improved in the next release. The contribution of different rainfall intensity intervals to total monsoon rainfall is captured well by the IMERG estimates. However, IMERG-F V6 exhibits better performance in precipitation estimation and detection of rainy days during the GPM period (2014–2017) than the pre-GPM period (2010–2013). Similarly, both near-real-time and research products show similar characteristics in the detection of rainy days. Both V5 and V6 IMERG-F estimates show similar error characteristics in daily precipitation estimation over the country. Bias in all-India daily mean rainfall in the near-real-time IMERG products is about 3–4 times larger than research product. However, near-real-time products have larger errors than IMERG-F V6, as expected. The spatial distributions of different error metrics over the country show that both near-real-time IMERG products (e.g., Early and Late Runs) have similar error characteristics in precipitation estimation. In addition, the current version 6 of the IMERG research product or Final Run (IMERG-F V6) has been compared with its predecessor, version 5, and error characteristics of IMERG-F V6 for pre-GPM and GPM periods have been assessed. In this study, near-real-time and research products of IMERG have been extensively evaluated against a daily rain-gauge-based precipitation dataset over India for the southwest monsoon period. The IMERG provides global precipitation estimates at finer spatiotemporal resolution (e.g., 0.1°/half-hourly) and has shown to be better than other contemporary multi-satellite precipitation products over most parts of the globe. Following the launch of the Global Precipitation Measurement (GPM) Core Observatory, the Integrated Multi-satellite Retrievals for GPM (IMERG) precipitation product was released. Accurate estimation of precipitation is vital for numerous applications ranging from hydrology to climatology. Precipitation is one of the integral components of the global hydrological cycle.
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