Submitted to: Journal of Remote Sensing Society of Japan
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/15/2008
Publication Date: 3/1/2009
Citation: Jackson, T.J., Bindlish, R., Cosh, M.H. 2009. Validation of AMSR-E soil moisture products using in situ observations. Journal of the Remote Sensing Society of Japan. 29:263-270.
Interpretive Summary: Soil moisture products from satellite sensors have to be validated because the retrieval algorithms utilize formulations, parameters and ancillary data that have not been thoroughly developed and verified. An evaluation of the global soil moisture products generated by NASA and the Japanese Aerospace Exploration Agency was conducted. The JAXA and NASA soil moisture products were compared to in situ observations derived from networks developed specifically for this purpose. An alternative approach, developed during the course of AMSR-E mission, was also evaluated using the in situ observations. The results indicate that each algorithm has different performance statistics that depend upon the site and that there is much room for improvement in the algorithms adopted by JAXA and NASA. A positive outcome of the analysis is that it appears that the algorithms can perform within reasonable error bounds. The results in this study are important in validation and quantification of errors associated with different AMSR-E soil moisture algorithms. These soil moisture products will eventually be employed to improve soil moisture monitoring for crop production estimates world-wide by USDA-Foreign Agricultural Service and for improving weather forecast models being run by NOAA and other agencies.
Technical Abstract: The Advanced Microwave Scanning Radiometer (AMSR) program was the first to implement a soil moisture algorithm development and validation program that would lead to global standard products. A key aspect of the program was the inclusion of multiple research algorithms with continuing evaluation. One approach is the single channel algorithm (SCA) that utilizes the AMSR channel with maximum sensitivity in combination with ancillary data on vegetation conditions. Over the course of the AMSR project, this approach has been developed and improved. A critical component of providing a standard soil moisture product is its validation. As part of the AMSR validation program networks of dedicated validation sites were developed. These networks provide estimates of the average soil moisture over watersheds and surrounding areas that approximate the size of the AMSR footprint. Measurements have been made on a continuous basis since 2002. The NASA and JAXA standard soil moisture products were compared to the network observations, along with an alternative single channel algorithm (SCA). The results indicate that each algorithm has different performance statistics that depend upon the site and that there is much room for improvement in the algorithms adopted by JAXA and NASA. They also illustrate the potential pitfalls in using the products without caution.