Spatial Scaling of Water and Energy Fluxes in a Tall-Grass Prairie

Understanding the spatial scaling behavior of evapotranspiration and its relation to controlling factors on the land surface is necessary for accurate estimates of regional water and energy cycling. Combining MODIS imagery with a soil-vegetation-atmosphere transfer scheme, we are able to compute spatially distributed surface energy fluxes for the Konza prairie in North-central Kansas. Comparison with three eddy-covariance stations and a large aperture scintillometer demonstrate good agreement with the modeled fluxes. In order to ascertain the spatial scaling behavior, a combination of wavelet multi-resolution analysis and information theory metrics are utilized. Results indicate that the spatial variability in surface radiometric temperature primarily determines the spatial variability in surface fluxes. In addition, small scale variability in the water flux can be ascribed to the small scale heterogeneity in vegetation cover. Correlation analysis indicates general scale invariance across a range of scales. This suggests that low spatial resolution data (e.g. 1 km) may be adequate for accurately determining water cycling in prairie ecosystems.