Simulating the synoptic climatology of extreme precipitation events under global warming
William J. Gutowski Jr., Iowa State University, Ames, IA; and S. S. Willis, J. C. Patton, B. R. Schwedler, R. W. Arritt, and E. S. Takle
We analyze the ability of regional climate models (RCMs) to simulate extreme regional precipitation, using observations from co-operative network observing sites and model results from 10-year RCM simulations of present and future-scenario climates. In our initial analysis, we examine an Upper Mississippi River Basin region for daily precipitation events during the cold half of the year (September-March) that have intensities in the top 0.05% and that cover several observation sites or model grid points. For both observed and simulated contemporary precipitation, nearly all such extreme regional events occur when a slow moving, cut-off-low system develops over the Rockies and Great Plains and steadily pumps moisture into the Upper Mississippi region from the Gulf of Mexico. The model shows similar circulation behavior for corresponding extreme events in its future scenario. However, the magnitude of daily precipitation in extreme events increases substantially in the future scenario, by 26%, compared to the 16% increase in average daily precipitation.
The results show the potential for RCMs to replicate well the extreme regional precipitation events seen in observations, supporting their use for projecting future changes in extreme events. The results also suggest robust circulation behavior for such extremes, even in the face of climate variability.
Extended Abstract (2.7M)
Session 1, Climate and Extreme Weather Events
Tuesday, 16 January 2007, 1:30 PM-5:30 PM, 214D
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