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Abstract

Precipitation is an important parameter of the essential climate variables in the Earth System and is a key variable in the global water cycle. However, surface observations of precipitation over oceans are relatively sparse. Satellite observations over oceans are the only viable means of monitoring the spatial distribution of precipitation. In an effort to improve global precipitation observations, the research community has developed a state-of-the-art precipitation dataset as part of the National Aeronautics and Space Administration/Japan Aerospace Exploration Agency Global Precipitation Measurement (GPM) program. One of the satellite-gridded products provides precipitation estimates using GPM and other satellite dataset is called Integrated Multi-satellitE Retrievals for GPM (IMERG). The highest resolution of IMERG products has a maximum spatial resolution of 0.1°×0.1° and temporal resolution of 30 min. Even with the recent advancements in satellite precipitation retrievals, there is a need to evaluate the uncertainty characteristics of IMERG precipitation estimates especially over oceans. To address this need, observations from Ocean Rainfall And Ice-phase precipitation measurement Network (OceanRAIN) project have been used to demonstrate the usefulness in evaluating IMERG precipitation products over the ocean. The OceanRAIN dataset was created using observations from the ODM-470 optical disdrometer that has been deployed on 12 research vessels worldwide with 6 long-term installations operating in all climatic regions, seasons, and ocean basins. More than 11.5 million 1-min observations have been collected during the OceanRAIN program. For this study, more than 5.6 million 1-min observations were used in the comparison period of March 20, 2014–December 31, 2018, which coincides with GPM IMERG products.