Review of Gridded Climate Products and Their Use in Hydrological Analyses Reveals Overlaps, Gaps, and Need for More Objective Approach to Model Forcings

Abstract. Climate forcing data accuracy drives performance of hydrologic models and analyses, yet each investigator needs to select from among the numerous gridded climate dataset options and justify their selection for use in a particular hydrologic model or analysis. This study aims to provide a comprehensive compilation and overview of gridded datasets (precipitation, air temperature, humidity, windspeed, solar radiation) and considerations for climate product selection criteria for hydrologic modelling and analyses. All datasets summarized here span at least the coterminous U.S. (CONUS), and many are continental or global in extent. Gridded datasets built on ground-based observations (17), satellite imagery (20), and/or reanalysis products (23) are compiled and described, with focus on the characteristics that hydrologic investigators may find useful in discerning acceptable datasets (variables, coverage, resolution, accessibility, latency). Best-available-science recommendations for dataset selection are based on a review of 28 recent studies (past 10 years) that compared performance of various gridded climate datasets for hydrologic analyses. No single best source of gridded climate data exists, but several common themes arose. Gridded daily temperature datasets improved when derived over regions with greater station density. Similarly, gridded daily precipitation data were more accurate when derived over regions with higher-density station data, when used in spatially less-complex terrain, and when corrected using ground-based data. In mountainous regions as well as humid regions, reanalysis-based datasets generally performed better than ground-based when underlying data had low station density, but for higher station densities, there was no difference. Ground-based precipitation datasets generally performed better than satellite- or reanalysis-based datasets, though better precipitation and temperature datasets did not always translate into better streamflow modelling. Hydrologic analyses would benefit from improved gridded datasets that retain dependencies among climate variables and better represent small-scale spatial variability of climate variables in complex topography.