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

Yanhong Gao, L. Ruby Leung, Eric P. Salathé, Francina Dominguez, Bart Nijssen, Dennis P. Lettenmaier

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Abstract

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.

Original languageEnglish (US)
Article numberL09711
JournalGeophysical Research Letters
Volume39
Issue number9
DOIs
StatePublished - May 1 2012

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ASJC Scopus subject areas

  • Geophysics
  • Earth and Planetary Sciences(all)

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