|Can Oevelen, Peter|
Submitted to: Water Resources Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/11/1999
Publication Date: N/A
Citation: Interpretive Summary: The variability in surface soil moisture within crop and rangeland fields were studied. This effort was part of the Southern Great Plains Hydrology Experiment. Distinct differences were found to be associated with known variations in soil types, vegetation cover, and rainfall gradients. Local agricultural practices (row structure and terracing) were found to have a major impact on soil moisture variations. The statistical distribution properties varied with the level of wetness. These results provide critical information in developing validation schemes for interpreting remotely sensed data and in parameterizing soil moisture components of hydrologic and climate models.
Technical Abstract: Surface soil moisture content is highly variable in both space and time. While remote sensing provides an effective methodology for mapping surface moisture content over large areas, it averages within-pixel variability, thereby making the underlying heterogeneity observed at the land surface. This variability must be better understood in order to rigorously evaluate sensor performance, and to enhance the utility of the larger-scale remotely-sensed averages by quantifying the underlying variability that remote sensing cannot record explicitly. In support of the Southern Great Plains 1997 (SGP97) Hydrology Experiment (a surface soil moisutre mapping mission conducted between June 18 and July 17, 1997 in central Oklahoma) an investigation was conducted to characterize soil moisture variability within remote sensing footprints (approximately 0.64-km2) with more certainty than would be afforded with conventional gravimetric moisture content sampling. The range and temporal dynamics of the variability in moisture content within each of the 6 fields are described, as are general relationships between the variability and footprint-mean moisture content. Results indicate that distinct differences in mean moisture content between the 6 sites are consistent with variations in soil type, vegetation cover, and rainfall gradients. Within fields, the standard deviation, coefficient of variation, skewness and kurtosis increased with decreasing moisture content. Agricultural practices of row-tilling and terracing were shown to exert a major control on observed moisture content variations.