Precipitation Extremes in Precipitation Extremes in Western U.S. Urban Areas: Western U.S. Urban Areas: How Reliable are Regional How Reliable are Regional Climate Model Projections Climate Model Projections Vimal Mishra Vimal Mishra 1 , Francina Dominguez , Francina Dominguez 2 , and , and Dennis P. Lettenmaier Dennis P. Lettenmaier 1 1 Civil and Environmental Engineering, University of Washington, Seattle, WA 2 University of Arizona, Tucson, AZ W Climate Science Conference,2011 [email protected]1
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Precipitation Extremes in Western U.S. Urban Areas: How Reliable are Regional Climate Model Projections Vimal Mishra 1, Francina Dominguez 2, and Dennis.
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Precipitation Extremes in Western Precipitation Extremes in Western U.S. Urban Areas: How Reliable U.S. Urban Areas: How Reliable
are Regional Climate Model are Regional Climate Model ProjectionsProjections
Vimal MishraVimal Mishra11, Francina Dominguez, Francina Dominguez22, and Dennis P. , and Dennis P. LettenmaierLettenmaier11
1Civil and Environmental Engineering, University of Washington, Seattle, WA
“there is now mounting evidence to suggest that a warmer climate will be one in which the hydrological cycle will in general be more intense, leading to more heavy rain events” (IPCC, 1996)
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Intensified Hydrologic Cycle
More Precipitation Extremes
Warmer Climate
Precipitation Extremes
4Groisman et al., 2005, J. of Climate
Trends in heavy and very heavy rain events
Human contribution to more-intense precipitation extremes
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S-K Min et al. Nature 470, 378-381 (2011) doi:10.1038/nature09763
Given that atmospheric water-holding capacity is expected to increase roughly exponentially with temperature—and that atmospheric water content is increasing in accord with this theoretical expectation—it has been suggested that human-influenced global warming may be partly responsible for increases in heavy precipitation.
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Need for the regional climate models for precipitation extremes
Source: NCAR
Spatial resolution of GCMs is too coarse to resolve the processes that control precipitation extremes
RCMs partially resolved finer scale variability related to topography and land cover
However, RCMs have been evaluated for precipitation extremes in urban areas
Precipitation Extremes and Urban Areas
• About 80% of U.S. population lives in urban areas
• Urban areas have large infrastructure and wealth and precipitation extremes may cause more damage than expected
• Increasing precipitation extremes may lead to substantial changes in drainage water infrastructure
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August 8, 2007, 8:49 AMFlooding Cripples Subway System (New York Times)
HEAVY RAIN CAUSES MORE FLOODING IN CHICAGO SUBURBSFriday, August 24, 2007
Precipitation Extremes in Urban Areas
Introduction
• So far relatively little work has been done evaluating the ability of RCMs to simulate precipitation extremes in major urban areas in U.S.
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Science QuestionHow effective are RCM-downscaled climate simulations in reconstructing observed sub-daily to daily scale precipitation extremes over the major urban areas in the western United States?
Study Region
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20 major urban areas across the Western United States Hourly precipitation data from the nearby stations
Data
Observed hourly precipitation data from NCDC RCMs simulated 3-hourly data from North
American Regional Climate Change Program (NARCCAP)