Evaluation of a Reanalysis‐Driven Configuration of WRF4 Over the Western United States From 1980 to 2020

Dynamical downscaling remains a powerful tool for studying regional climate processes, and the genesis of high-resolution historical future data. This technique is particularly important over areas complex terrain, such as western United States (WUS), where global models are especially limited in representing climate. After identifying suite WRF options that best simulate snow precipitation an average water year (2010) WUS, we evaluate performance dynamically downscaled European Centre Medium-range Weather Forecasting's fifth Reanalysis (ERA5) from 1980 to 2020 on 45-km, 9-km, two 3-km grids. We find by decreasing horizontal grid spacing within WRF, improvements Sierra Nevada Northern Rocky Mountain snow, Santa Ana Diablo winds, coastal meteorology occur. For landfalling atmospheric rivers (ARs), reanalysis simulates greater upstream integrated vapor transport (IVT) than ERA5. However, skillfully positioning IVT timing magnitude AR precipitation. potential bias, conjunction with increasing resolution, leads wet bias across experiment. conclusion supported streamflow analysis, although note experiment can also be explained situ undercatch issues. Meanwhile, 9-km more biased Mountains compared measured SWE precipitation, indicating geographic sensitivity biases.