UC Irvine

We investigate spatial patterns of daily precipitation field in the western United States, in order to improve assessment and disaggregation of climate model simulation. Empirical Orthogonal Function (EOF) analysis reveals that the spatial pattern of daily precipitation has not changed saliently in the region over the period 1948-2008. Results show that, even at very fine spatial (.25 × .25°) and temporal (daily) resolutions, a small number (∼15) of leading EOFs can explain about 90% of the total variance of the timeseries of the entire precipitation field, having more than 6,000 grid cells. Moreover, the identified leading EOFs demonstrate consistency over time and across different spatial resolutions. Utilizing this consistency, an empirical method of disaggregating the precipitation output of climate models in this region is introduced. Illustrative results exhibit the feasibility and potency of this method. The advantages and limitations of this method are discussed as well. Copyright © 2011 by the American Geophysical Union.