Geophysical Research Letters

Moisture flux convergence in regional and global climate models: Implications for droughts in the southwestern United States under climate change

Authors

  • Yanhong Gao,

    1. Department of Civil and Environmental Engineering, University of Washington, Seattle, Washington, USA
    2. Key Laboratory of Land Surface Process and Climate Change in Cold and Arid Regions, Chinese Academy of Sciences, Lanzhou, China
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  • L. Ruby Leung,

    1. Atmospheric Sciences and Global Change Division, Pacific Northwest National Laboratory, Richland, Washington, USA
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  • Eric P. Salathé Jr.,

    1. Science and Technology Program, University of Washington, Bothell, Washington, USA
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  • Francina Dominguez,

    1. Department of Atmospheric Sciences and Department of Hydrology and Water Resources, University of Arizona, Tucson, Arizona, USA
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  • Bart Nijssen,

    1. Department of Civil and Environmental Engineering, University of Washington, Seattle, Washington, USA
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  • Dennis P. Lettenmaier

    Corresponding author
    1. Department of Civil and Environmental Engineering, University of Washington, Seattle, Washington, USA
      Corresponding author: D. P. Lettenmaier, Department of Civil and Environmental Engineering, University of Washington, Box 352700, Seattle, WA 98195-2700, USA. (dennisl@u.washington.edu)
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Corresponding author: D. P. Lettenmaier, Department of Civil and Environmental Engineering, University of Washington, Box 352700, Seattle, WA 98195-2700, USA. (dennisl@u.washington.edu)

Abstract

[1] The water cycle of the southwestern United States (SW) is dominated by winter storms that maintain a positive annual net precipitation. Analysis of the control and future climate from four pairs of regional and global climate models (RCMs and GCMs) shows that the RCMs simulate a higher fraction of transient eddy moisture fluxes because the hydrodynamic instabilities associated with flow over complex terrain are better resolved. Under global warming, this enables the RCMs to capture the response of transient eddies to increased atmospheric stability that allows more moisture to converge on the windward side of the mountains by blocking. As a result, RCMs simulate enhanced transient eddy moisture convergence in the SW compared to GCMs, although both robustly simulate drying due to enhanced moisture divergence by the divergent mean flow in a warmer climate. This enhanced convergence leads to reduced susceptibility to hydrological change in the RCMs compared to GCMs.

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