Synergistic Use of Scatterometer and Scansar Data for Extraction of Surface Soil Moisture Information in Australia

The potential of the ERS-1/2 scatterometer global soil moisture product has been shown in several studies. The ASCAT sensor on-board the METOP satellite is extending the 16 year time series of the ERS-1/2 scatterometer as a source for extracting information for ocean and land applications. Calibrated ASCAT data will continue the scatterometer global soil moisture archive while improving both the spatial and temporal resolution. A disaggregation scheme for spatial downscaling of the ASCAT soil moisture product, using a temporal stability analysis of medium resolution ScanSAR data from the ENVISAT ASAR sensor, has been developed. Furthermore, by transferring the change detection algorithm from the scatterometer to the ScanSAR data, also a 1 km Surface Soil Moisture product has been derived. The disaggregated scatterometer soil moisture product is evaluated in conjunction with the 1 km Surface Soil Moisture product in Australia. The influence of land cover on the performance of the products is considered. Both high resolution products perform best in areas with less dense vegetation, such as agricultural lands and crop land. In areas with a dense vegetation canopy or deserts, the uncertainties in the extracted soil moisture values are large. The disaggregated product, while implicitly taking into account effects of land cover and surface roughness at different scales, provide a statistical approach to downscale regional soil moisture measurements to a finer spatial scale.