HR: 0800h
AN: GC21A-0136    [Abstracts]
TI: Dynamical Downscaling Technique for Global Climate Model
AU: * Yoshimura, K
EM: k1yoshimura@ucsd.edu
AF: Scripps Institution of Oceanography, UCSD, 9500 Gilman Dr., MC0224, La Jolla, CA 92093-0224, United States
AU: * Yoshimura, K
EM: k1yoshimura@ucsd.edu
AF: Institute of Industrial Science, The University of Tokyo, 4-6-1 Komaba, Meguro, Tokyo, 153- 8505, Japan
AU: Kanamitsu, M
EM: mkanamitsu@ucsd.edu
AF: Scripps Institution of Oceanography, UCSD, 9500 Gilman Dr., MC0224, La Jolla, CA 92093-0224, United States
AB: Aiming at producing higher resolution global reanalysis datasets from coarse 200 km resolution reanalysis, a global version of the dynamical downscaling using a global spectral model (GSM) is developed. A variant of spectral nudging, the scale-selective bias correction (SSBC) developed for regional models is modified in the following manner to adapt it to the global domain; 1) temperature is nudged in addition to the zonal and meridional components of winds, and 2) humidity is excluded from any nudging or correction. The downscaling was performed using T248L28 (about 50 km resolution) global model for 2001, driven by NCEP/NCAR Reanalysis 2 (T62L28 resolution). Evaluation with high-resolution observations showed that the monthly averaged surface temperature and daily variation of precipitation become better than the Reanalysis over the globe. It was found that humidity plays a significant role for a significant positive bias of global precipitation in the downscaled simulation. Over North America, surface wind speed and temperature become better, and over Japan, the diurnal pattern of surface temperature is much improved, as are wind speed and precipitation, but not humidity. This study suggests that the global downscaling is a viable and economical method to obtain high- resolution reanalysis without re-running a very expensive high-resolution full data assimilation.
DE: 0429 Climate dynamics (1620)
DE: 1223 Ocean/Earth/atmosphere/hydrosphere/cryosphere interactions (0762, 1218, 3319, 4550)
DE: 1626 Global climate models (3337, 4928)
DE: 1854 Precipitation (3354)
DE: 3315 Data assimilation
SC: Global Environmental Change [GC]
MN: 2007 Fall Meeting