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PCMDI > WCRP CMIP3 Model Output > Diagnostic Subprojects Printer Friendly Version
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Projected Changes in Southwest United States Climate Using Observational Data and IPCC Scenarios

PI: Eileen Hall-McKim
Institution: National Oceanic and Atmospheric Administration
1) Introduction
The possibility of future climate change has enormous significance for western water management, particularly for planning and designing infrastructure for future water requirements. Most models suggest substantial warming over much of North America, including the West. Models indicate a likely acceleration of continental warming over the 21st century and an intensification of the hydrological cycle (IPCC 2001). Even without changes in precipitation, such warming would have major implications for western water management. Improved climate-change projections on regional scales are urgently needed for the benefit of those who deal with water resources (Lewis et al. 2003). Predictions of potential climate change are developed through analyses of observed relationships compared with projections by physically based climate models.

Problem: Examine model scenarios of precipitation for the southwest U.S. for late 21st century compared with observational data for the late 20th century.

2) Proposed Data
Study area is the southwest U.S. region of Arizona and New Mexico located between 32 N - 37 N, 104.5 W - 114.5 W
a) Observed precipitation data from the Cooperative Station Network of the National Weather Service for the years 1981-2001
b) Output from 2 IPCC GCMs (e.g. Hadley and Canadian)scenarios for 2061-2081. (check resolution, reasons for selecting)

3)Analysis of observations
Analysis of anomalous wet/dry years; seasonal, monthly, and interannual composites of Arizona and New Mexico (AZNM) precipitation for the years 1948 - 2005. The figures are derived by the use of Fortran programs written to produce maps of daily, monthly, annual, climatology, and monsoon season (July-August) precipitation and circulation plots. Anomalous years are sorted into 10 wettest and 10 driest years according to precipitation values. Maps are produced of composite precipitation and wind vectors of 10 wettest/driest Julys, 10 wettest/driest Augusts, 10 wettest/driest months (July or August), and 10 wettest/driest monsoon seasons (July + August) of the data. This has been repeated for the three and five wettest/driest years for comparison to examine the stability of the composites. Individual anomalous years are also plotted and mapped for precipitation and wind vectors. Case study months and years are selected for further analysis. This work is currently in progress.

4) Analysis of GCM control cases and comparison with observations
Control experiments vs. observational data for precipitation and temperature for selected models

5) Analytic comparison for the periods 1981 - 2001 vs 2061 - 2081
- Differences in precipitation fields between two GCMs for two scenarios (possibly SRES A1 and SRES B1).
- Interpretation of projected changes - means, variability.
- Examine some of IPCC extreme indices

6) Discussion and Regional implications

7) Conclusions/future directions

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    Lawrence Livermore National Laboratory  |  Physical & Life Sciences Directorate