FY2010 - Oak Ridge National Laboratory

Director’s R&D Fund—
General
2000), the U.S. Daily time-series station data contributing to those normals, and daily precipitation and
temperature extremes were obtained from the National Climatic Data Center. From analysis of
CCSM_control simulation results for the period 2000–2005, and using the NCEP_WRF simulations at
4 km resolution as the reference baseline, we find that bias, standard error, and spatial variance decline as
spatial resolution of the WRF downscaling increases from 64 to 16 to 4 km for both heating degree days
(HDD) and the intensity of heat waves. Bias and spatial variance in cooling degree days (CDD) also
decline as spatial resolution increases, but standard error in CDD shows no such scale dependency. At
least part of the bias reduction for CDD is associated with better resolution of the mountains northeast of
Phoenix. Results for precipitation particularly with regards to extremes are less clear, perhaps because of
the relatively short simulations available for the analyses, but average daily precipitation does appear to
be better simulated with increased downscaling resolution.
Information Shared
Das, D., E. Kodra, K. Steinhaeuser, S.-C. Kao, A. R. Ganguly, M. L. Branstetter, D. J. Erickson,
R. Flanery, M. Martinez Gonzalez, C. Hays, A. W. King, W. Chris Lenhardt, R. Oglesby, R. M.
Patton, C. M. Rowe, A. Sorokine, and C. Steed. 2010. “Uncertainty and Extremes Analysis to
Evaluate Dynamical Downscaling of Climate Models.” Abstract and presentation, 2010 American
Geophysical Union (AGU) Fall Meeting, San Francisco.
172