Evaluating the water cycle over CONUS at the watershed scale for the Energy Exascale Earth System Model version 1 (E3SMv1) across resolutions

Abstract

The water cycle is an important component of the earth system and it plays a key role in many facets of society, including energy production, agriculture, and human health and safety. In this study, the Energy Exascale Earth System Model version 1 (E3SMv1) is run with low-resolution (roughly 110 km) and high-resolution (roughly 25 km) configurations -as established by the High Resolution Model Intercomparison Project protocol -to evaluate the atmospheric and terrestrial water budgets over the conterminous United States (CONUS) at the large watershed scale. The water cycle slows down in the HR experiment relative to the LR, with decreasing fluxes of precipitation, evapotranspiration, atmospheric moisture convergence, and runoff. The reductions in these terms exacerbate biases for some watersheds, while reducing them in others. For example, precipitation biases are exacerbated at HR over the Eastern and Central CONUS watersheds, while precipitation biases are reduced at HR over the Western CONUS watersheds. The most pronounced changes to the water cycle come from reductions in precipitation and evapotranspiration, the latter of which results from decreases in evaporative fraction. While the HR simulation is warmer than the LR, moisture convergence decreases despite the increased atmospheric water vapor, suggesting circulation biases are an important factor. Additional exploratory metrics show improvements to water cycle extremes (both in precipitation and streamflow), fractional contributions of different storm types to total precipitation, and mountain snowpack.

Recreating the California New Year's Flood Event of 1997 in a Regionally Refined Earth System Model

“…(2022), while Harrop et al. (2022) provides additional details on water cycle process fidelity in both the atmosphere and land‐surface in E3SM at uniform horizontal resolutions of 1.00° versus 0.25° over the United States.…”

“…A detailed description of E3SMv2's atmospheric dynamical core, physics and dynamics, horizontal grids, vertical discretization, radiation, tracer transport schemes, and subgrid-scale parameterization choices (e.g., cloud microphysics scheme) can be found in Golaz et al (2022). More specific findings related to RRM-E3SM are described in Tang et al (2022), while Harrop et al (2022) provides additional details on water cycle process fidelity in both the atmosphere and land-surface in E3SM at uniform horizontal resolutions of 1.00° versus 0.25° over the United States.…”