Hydrology and Earth System Sciences www.hydrol-earth-syst-sci.net 1027-5606 1607-7938 12 1 2008 10.5194/hess-12-39-2008 http://www.hydrol-earth-syst-sci.net/12/39/2008/ http://www.hydrol-earth-syst-sci.net/12/39/2008/hess-12-39-2008.html http://www.hydrol-earth-syst-sci.net/12/39/2008/hess-12-39-2008.pdf 39 53 2008-01-23 Generation of soil moisture patterns at the catchment scale by EOF interpolation M. A. Perry J. D. Niemann jniemann@engr.colostate.edu Colorado Division of Water Resources Pueblo, CO 81004, USA Department of Civil and Environmental Engineering, Colorado State University Fort Collins, CO 80523, USA Spatial patterns of soil moisture cannot be adequately characterized by direct measurement for most practical applications, so interpolation between observations is required. Interpolation of soil moisture is complicated because multiple hydrologic processes can affect soil moisture and these processes can introduce distinct modes of variation into the soil moisture patterns. In this paper, a new method to interpolate soil moisture data is presented. This method accepts a dataset of soil moisture at widely-spaced locations on multiple dates and produces fine-scale patterns of soil moisture on the same dates. The method first uses Empirical Orthogonal Function (EOF) analysis to decompose the dataset into a set of time-invariant patterns of covariation (EOFs) and a set of associated time series (called expansion coefficients or ECs) that indicate the importance of the patterns on each date. The method then uses a statistical test to retain only the most important EOFs, and these EOFs are interpolated to the desired resolution using a standard estimation or interpolation method. 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