California winter precipitation change under global warming in the Coupled Model Intercomparison Project 5 ensemble

J. David Neelin, Baird Langenbrunner, Joyce E. Meyerson, Alex Hall, and Neil Berg

J. Climate, 26, 6238-6256, doi:10.1175/JCLI-D-12-00514.1. Paper (PDF 4.3 MB).
© Copyright 2013 by the American Meteorological Society.

Abstract:
Projections of possible precipitation change in California under global warming have been subject to considerable uncertainty because California lies between the region anticipated to undergo increases in precipitation at mid-to-high latitudes and regions of anticipated decrease in the subtropics. Evaluation of the large-scale model experiments for Coupled Model Intercomparison Project 5 (CMIP5) suggests a greater degree of agreement on the sign of the winter (December-February) precipitation change than in the previous such intercomparison, indicating a greater portion of California falling within the increased precipitation zone. While the resolution of global models should not be relied on for accurate depiction of topographic rainfall distribution within California, the precipitation changes depend substantially on large-scale shifts in the storm tracks arriving at the coast. Significant precipitation increases in the region arriving at the California coast are associated with an eastward extension of the region of strong Pacific jetstream, which appears to be a robust feature of the large-scale simulated changes. This suggests that effects of this jet extension in steering storm tracks toward the California coast constitute an important factor that should be assessed for effects on incoming storm properties for high resolution regional model assessments.

Citation. Neelin, J. D., B. Langenbrunner, J. E. Meyerson, A. Hall, and N. Berg: California winter precipitation change under global warming in the Coupled Model Intercomparison Project 5 ensemble. J. Climate, 26, 6238-6256, doi:10.1175/JCLI-D-12-00514.1.

Acknowledgments. This work was supported in part by the NOAA Climate Program Office Modeling, Analysis, Predictions and Projections (MAPP) Program under grant NA11OAR4310099 as part of the CMIP5 Task Force and National Science Foundation grant AGS-1102838. We acknowledge the World Climate Research Programme's Working Group on Coupled Modelling, which is responsible for CMIP, and we thank the climate modeling groups (listed in Table 1 of this paper) for producing and making available their model output. For CMIP the U.S. Department of Energy's Program for Climate Model Diagnosis and Intercomparison provides coordinating support and led development of software infrastructure in partnership with the Global Organization for Earth System Science Portals.
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