Validation of IMERG Oceanic Precipitation over Kwajalein

The integrated Multi-satellitE Retrievals for GPM (IMERG) Version V05B and V06B precipitation products from the Global Precipitation Measurement (GPM) mission are validated against ground-based observations Kwajalein Polarimetric S-band Weather Radar (KPOL) deployed at Atoll in central Pacific Ocean. Such a validation is particularly important as comprehensive surface measurements over oceans practically infeasible, which hampers identification of possible errors, improvement future versions IMERG other satellite-based retrieval algorithms. their native 0.1°, 30 min resolution 2014 to 2018 based on both volumetric categorical metrics. This study indicates that rates underestimated with respect radar estimates, but underestimation much reduced V06B. outperforms systematic bias improved detectability. performance further traced back its individual sensors morphing-based overall mainly driven by negative relative biases algorithms largely corrected Imagers perform generally better than sounders because usage low-frequency channels imagers can detect emission signals hydrometeors. Among imagers, Microwave Imager (GMI) Advanced Scanning Radiometer 2 (AMSR2) best, followed Special Sensor Imager/Sounder (SSMIS). sounders, Humidity Sounder (MHS) Technology (ATMS) Atmospheric Profiling Intertropics Radiometry (SAPHIR) all categories, morph-only IR + morph only SAPHIR. SAPHIR shows worst among likely due limited channel selection. It envisaged these results will improve our understanding aid IMERG.