Comparison of Gridded Precipitation Datasets Used in Climate and Drought Monitoring

Estimates of precipitation from gridded datasets are routinely used in climate monitoring, yet considering the challenges associated with measuring precipitation, these gridded estimates can be substantially different. As a result, the conclusions one might reach regarding drought conditions could vary depending on the dataset that is chosen. In this study, six gridded daily precipitation datasets---namely PRISM; NOAA's MRMS, nClimGrid, Stage IV (aka AHPS), and CCPA; and ECMWF's ERA5, are compared over six water years (2018-2023) over the United States. The gridded estimates are also compared against gauge observations from COOP and CoCoRaHS stations. Consistent biases from year to year are found in several of the datasets; for example overestimates in the Stage IV analysis in the Missouri River Basin and underestimates in mountainous areas for the products that rely heavily on radar data. The implications of these results for climate and drought monitoring will be discussed.