Preprints
https://doi.org/10.5194/gmd-2021-364
https://doi.org/10.5194/gmd-2021-364

Submitted as: model evaluation paper 22 Nov 2021

Submitted as: model evaluation paper | 22 Nov 2021

Review status: this preprint is currently under review for the journal GMD.

Atmospheric River Representation in the Energy Exascale Earth System Model (E3SM) Version 1.0

Sol Kim1,2, L. Ruby Leung2, Bin Guan3,4, and John C. H. Chiang1 Sol Kim et al.
  • 1Department of Geography, University of California, Berkeley, CA, USA
  • 2Pacific Northwest National Laboratory, Richland, WA, USA
  • 3Joint Institute for Regional Earth System Science and Engineering, University of California, Los Angeles, CA, USA
  • 4Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, USA

Abstract. The Energy Exascale Earth System Model (E3SM) Project is an ongoing, state-of-the-science Earth system modeling, simulation, and prediction project developed by the U.S. Department of Energy (DOE). With an emphasis on supporting DOE's energy mission, understanding and quantifying how well the model simulates water cycle processes is of particular importance. Here, we evaluate E3SM version v1.0 for its ability to represent atmospheric rivers (ARs), which play significant roles in water vapor transport and precipitation. The characteristics and precipitation associated with global ARs in E3SM at standard resolution (1° × 1°) are compared to the Modern-Era Retrospective analysis for Research and Applications, Version 2 (MERRA2). Global pattern of AR frequencies in E3SM show high degrees of correlation (>= 0.97) with MERRA2 and low mean absolute errors (< 1 %) annually, seasonally, and across different ensemble members. However, some large-scale condition biases exist leading to AR biases - most significant of which are: the double-ITCZ, a stronger and/or equatorward shifted subtropical jet during boreal and austral winter, and enhanced northern hemisphere westerlies during summer. By comparing atmosphere-only and fully coupled simulations, we attribute the sources of the biases to the atmospheric component or to a coupling response. Using relationships revealed in Dong et al. (2021), we provide evidence showing the stronger north Pacific jet in winter and enhanced northern hemisphere westerlies during summer associated with E3SM's double-ITCZ and related weaker AMOC, respectively, are the sources of much of the AR biases found in the coupled simulations.

Sol Kim et al.

Status: open (until 17 Jan 2022)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse

Sol Kim et al.

Sol Kim et al.

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Short summary
The Energy Exascale Earth System Model Project is a state-of-the-science Earth system model developed by the U.S. Department of Energy. Understanding how the water cycle behaves in this model is of particular importance to the DOE’s mission. Atmospheric rivers play a crucial role in the global water cycle – moving vast amounts of water vapor through the sky and producing rain and snow. Thus, we evaluate E3SM for its ability to represent AR and find that E3SM can reliably simulate ARs globally.