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The ERA5 (reference C3S, 2017) global climate reanalysis assimilates observations of different meteorological quantities across the globe into a numerical model of atmospheric dynamics. It produces a large variety of output quantities including precipitation. ERA5 output is available in the CDS by C3S (https://cds.climate.copernicus.eu/cdsapp#!/dataset/reanalysis-era5-single-levels?tab=overview) in hourly intervals and as monthly means at 0.25° spatial resolution. Known issues are listed in the documentation; none of these relates directly to precipitation (as of 21/12/2018), but links between precipitation-related processes and respective issues may well exist.
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Copernicus Climate Change Service (C3S) (2017): ERA5: Fifth generation of ECMWF atmospheric reanalyses of the global climate. Copernicus Climate Change Service Climate Data Store (CDS), 21/12/2018. https://cds.climate.copernicus.eu/cdsapp#!/home
Goddard Earth Sciences Data and Information Services Center (2016), TRMM (TMPA) Precipitation L3 1 day 0.25 degree x 0.25 degree V7, Edited by Andrey Savtchenko, , Goddard Earth Sciences Data and Information Services Center (GES DISC), doi: 10.5067/TRMM/TMPA/DAY/7
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