Submitted to: American Geophysical Union
Publication Type: Abstract Only
Publication Acceptance Date: 10/20/2007
Publication Date: 12/9/2007
Citation: Bindlish, R., Jackson, T.J., Du, J., Cosh, M.H., Li, L. 2007. Soil moisture estimation using WindSat based passive microwave polarimetric observations [abstract]. EOS Transactions, American Geophyscial Union, Fall Supplements. 88(52):H33I-03.
Technical Abstract: Global soil moisture estimates are critical to study its role in weather and climate. Microwave remote sensing is the most feasible technique for large-scale soil moisture observations. Efforts have been made towards the goal of obtaining accurate satellite-based soil moisture products. Low frequencies (1.4 GHz) are preferable for soil moisture retrieval since perturbing factors such as vegetation are less significant. WindSat is a spaceborne multi-frequency polarimetric microwave radiometer operating at 6.8, 10.7, 18.7, 23.8 and 37.0 GHz. WindSat covers a 1025 km swath at an incidence angle of 53 degrees. WindSat has a sun synchronous polar orbit with a descending node at 6:00 AM. There is a growing interest of using WindSat observations for retrieving land variables. In this study, single channel algorithm is applied to WindSat data to estimate global soil moisture. This is the first attempt to do global estimates of soil moisture from WindSat observations. These estimates will complement soil moisture estimates from AMSR-E observations. Comprehensive validation work has been done by comparing the retrievals with in situ soil moisture observations from the networks at four carefully designed satellite soil moisture validation sites. The four watersheds have very different climate and vegetation conditions. The overall SEE of soil moisture for the four watersheds is 0.038 m3/m3. Analysis shows that WindSat soil moisture retrievals for all four validation sites are reasonable with acceptable error bounds. Soil moisture estimates for both ascending and descending orbits were reasonable. The spatial distribution of soil moisture was consistent with the known global climatology.