Framework for Generating Spatially Distributed Soil Moisture for Heterogeneous Landscapes at Operational Scales

Soil moisture forms the interface at which the partitioning of the energy, carbon and water budget for the land-surface occurs. Its spatial and temporal variability impacts different fields of application at varying extent scales like agriculture at the field scale, meteorology at the regional scale and climate change assessment at the global scale. However, there exists a discrepancy in support scales of sparsely distributed observed soil moisture data which is of the order of a few centimeters and remote sensing support scales that are required by spatially distributed eco-hydrologic models. This research provides a framework to generate spatial patterns of soil moisture at the operational modeling scales. The framework comprises of determination of the dominant land-surface controls of near-surface soil moisture dynamics between point and satellite support scale (25.6 km); and developing a spatially transferable look-up table - Scale-Wetness-Heterogeneity (SWHET) cuboid to describe the spatial patterns of soil moisture redistribution for heterogeneous landscapes at different operational scales. The dominant land-surface factors controlling soil moisture distribution at different scales were determined by developing a Shannon entropy based technique and non-decimated wavelet transforms. It was found that the land-surface controls on soil moisture vary with hydro-climate and antecedent wetness conditions. In general, the effect of soil was found to reduce with coarsening support scale while the effect of topography and vegetation increased. The SWHET cuboid (Figure 1) is hydro-climate specific and describes the relationship between the spatial correlation structures of the dominant biophysical factor and soil moisture redistribution for regions with complex heterogeneity described using a novel heterogeneity index. The spatial transferability of the SWHET cuboid to generate spatial patterns of footprint scale soil moisture was tested between two similar hydro-climates (Iowa, U.S.A and Manitoba, Canada) and validates under certain wetness and land-surface heterogeneity conditions.