Moisture Flux Convergence in Regional and Global Climate Models: Implications for Droughts in the Southwestern United States under Climate Change

TitleMoisture Flux Convergence in Regional and Global Climate Models: Implications for Droughts in the Southwestern United States under Climate Change
Publication TypeJournal Article
Year of Publication2012
JournalGeophysical Research Letters
PagesL09711
Date Published05/2012
Abstract / Summary

The water cycle of the southwestern (SW) United States 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) show 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, which 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.

URLhttp://www.agu.org/pubs/crossref/2012/2012GL051560.shtml
DOI10.1029/2012GL051560
Journal: Geophysical Research Letters
Year of Publication: 2012
Pages: L09711
Date Published: 05/2012

The water cycle of the southwestern (SW) United States 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) show 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, which 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.

DOI: 10.1029/2012GL051560
Citation:
Gao, Y, LR Leung, EP Salathé Jr., F Dominguez, B Nijssen, and DP Lennenmaier.  2012.  "Moisture Flux Convergence in Regional and Global Climate Models: Implications for Droughts in the Southwestern United States under Climate Change."  Geophysical Research Letters L09711.  https://doi.org/10.1029/2012GL051560.