Comparison of Integrated Multisatellite Retrievals for GPM (IMERG) and TRMM Multisatellite Precipitation Analysis (TMPA) Monthly Precipitation Products: Initial Results

Abstract

aunched on 27 February 2014, the Global Precipitation Measurement (GPM) mission comprises an international constellation of satellites to provide the next generation of global observations of precipitation. Built upon the success of the widely used TRMM Multisatellite Precipitation Analysis (TMPA) products, the Integrated Multisatellite Retrievals for GPM (IMERG) products continue to make improvements in areas such as spatial and temporal resolutions and snowfall estimates, etc., which will be valuable for research and applications. During the transition from TMPA to IMERG, characterizing the differences between these two product suites is important in order for users to make adjustments in research and applications accordingly. In this study, the newly released IMERG Final Run monthly product is compared with the TMPA monthly product (3B43) in the boreal summer of 2014 and the boreal winter of 2014/15 on a global scale. The results show the IMERG monthly product can capture major heavy precipitation regions in the Northern and Southern Hemispheres reasonably well. Differences between IMERG and 3B43 vary with surface types and precipitation rates in both seasons. Over land, systematic differences are much smaller compared to those over ocean because of the similar gauge adjustment used in the two monthly products. Positive relative differences (IMERG > 3B43) are primarily found at low precipitation rates and negative differences (IMERG < 3B43) at high precipitation rates. Over ocean, negative systematic differences (IMERG < 3B43) prevail at all precipitation rates. Analysis of the passive microwave (PMW) and infrared (IR) monthly products from TMPA and IMERG shows the large systematic differences in the tropical oceans are closely associated with the differences in the PMW products.