Assessment of specific climate metrics using dynamically downscaled projections of the Lower Santa Cruz River Basin

Patrick Bunn, Hsin-I Chang, and Christopher Castro

Hydrology and Atmospheric Sciences
The University of Arizona

The Bureau of Reclamation expressed a desire to understand the evolution of the climate in Lower Santa Cruz River Basin (LSCRB), Arizona, principally for current and future water resource management. Two specific climate metrics important for water resource management are the timing of the monsoon onset and the length of the preceding dry  period. The CMIP5 General Circulation Models (GCMs) were dynamically downscaled using WRF in the LSCRB. The downscaled data were then evaluated to select those models that  best represent the North American Monsoon (NAM) for the historic period 1979­2005. The MPI and HadGem2 models have the most pronounced winter season precipitation to monsoon signal so were used for this project. Metrics in temperature and precipitation are compared using the dynamically downscaled GCMs and statistical downscaling of the GCMs (LOCA), to highlight any differences between the two methodologies. Initial results show consistency in temperature projections but differences in precipitation. The timing of monsoon onset is shifting earlier in the season, which counters results from Cook & Seager (2013). The domain considered here is a small portion in the north­west of the domain in Cook & Seager and fewer models/members are considered here.

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