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

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 t...

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Bibliographic Details
Published in:Geophysical research letters 2012-05, Vol.39 (9), p.n/a
Main Authors: Gao, Yanhong, Leung, L. Ruby, Salathé Jr, Eric P., Dominguez, Francina, Nijssen, Bart, Lettenmaier, Dennis P.
Format: Article
Language:English
Subjects:
Climate
Climate change
CLIMATE MODELS
CLIMATES
CLIMATIC CHANGE
COMPLEX TERRAIN
CONVERGENCE
Drought
DROUGHTS
DRYING
Earth
Earth sciences
Earth, ocean, space
Eddies
ENVIRONMENTAL SCIENCES
Exact sciences and technology
global
Global climate
Global climate models
Global warming
GREENHOUSE EFFECT
HYDRODYNAMICS
hydrologic
Hydrologic cycle
Hydrology
MOISTURE
Mountains
PRECIPITATION
RCM
regional
regional climate models
Regions
Simulation
southwestern
southwestern United States
STABILITY
STORMS
Stream flow
TRANSIENTS
U.S
WATER
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Summary: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. Key Points Net precipitation projections for the southwestern US differ RCMs better resolve transient eddies and their interactions with mountains As a result, RCMs show less drying for the southwestern US than paired GCMs
ISSN:0094-8276
1944-8007
DOI:10.1029/2012GL051560