Simulations of Present and Future Climates in the Western United States with Four Nested Regional Climate Models

Journal Article · Wed Mar 15 04:00:00 EST 2006 · Journal of Climate, 19(6):873-895

DOI:https://doi.org/10.1175/JCLI3669.1· OSTI ID:882958

Duffy, Phil; Arritt, R; Coquard, J; Gutowski, William; Han, J; Iorio, J; Kim, Jongil; Leung, Lai R; Roads, J; Zeledon, E

We analyze simulations of present and future climates in the western U.S. performed with four regional climate models (RCMs) nested within two global ocean-atmosphere climate models. Our primary goal is to assess the range of regional climate responses to increased greenhouse gases in available RCM simulations. The four RCMs used different geographical domains, different increased greenhouse gas scenarios for future-climate simulations, and (in some cases) different lateral boundary conditions. For simulations of the present climate, we compare RCM results to observations and to results of the GCM that provided lateral boundary conditions to the RCM. For future-climate (increased greenhouse gas) simulations, we compare RCM results to each other and to results of the driving GCMs. When results are spatially averaged over the western U.S., we find that the results of each RCM closely follow those of the driving GCM in the same region, in both present and future climates. This is true even though the study area is in some cases a small fraction of the RCM domain. Precipitation responses predicted by the RCMs are in many regions not statistically significant compared to interannual variability. Where the predicted precipitation responses are statistically significant, they are positive. The models agree that near-surface temperatures will increase, but do not agree on the spatial pattern of this increase. The four RCMs produce very different estimates of water content of snow in the present climate, and of the change in this water content in response to increased greenhouse gases.

• Research Organization: Pacific Northwest National Laboratory (PNNL), Richland, WA (US)
• Sponsoring Organization: USDOE
• DOE Contract Number: AC05-76RL01830
• OSTI ID: 882958
• Report Number(s): PNNL-SA-46110; KP1205030
• Journal Information: Journal of Climate, 19(6):873-895, Journal Name: Journal of Climate, 19(6):873-895
• Country of Publication: United States
• Language: English

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