Evaluation and Improvement of the Aqua/amsr-E Soil Moisture Algorithm
Hydrology and Remote Sensing Laboratory
2013 Annual Report
1a.Objectives (from AD-416):
The goal of this agreement is to assess the accuracy of the soil moisture products derived by NASA and other agencies from the satellite-based Aqua Advanced Microwave Scanning Radiometer (AMSR-E). This information will then be used to modify the currently used algorithms, resulting in more accurate assessments. These products are used by USDA and other agencies in weather, climate, and yield forecasts.
1b.Approach (from AD-416):
AMSR-E has successfully operated for over seven years and it is anticipated that its successors will be launched beginning in 2012, resulting in at least a 25-year period of record of soil moisture observations from this instrument. Considering these factors, at this point in time it is critical to carefully evaluate the performance of the baseline algorithm and, where necessary, to refine its structure and implementation. Key to this assessment and algorithm improvements is a robust validation of the products. Although there are a variety of techniques and resources that can contribute to validation, ground-based measurements are the most important in providing information that can lead to fundamental improvements in the algorithm. Data collected by ARS watershed research units and the NRCS over the life of AMSR-E will be acquired and analyzed to assess algorithm performance. From this we will identify changes that could be made to the current NASA algorithm to improve its performance. Soil moisture product validation will be continued using the established and well calibrated in situ observations described. The suite of watersheds will be expanded to include two new watersheds. The quality of the existing watersheds will be assessed and updates made to the instrumentation in order to insure continuity through AMSR-E and the next generation of satellites. In order to effectively use data from numerous national and international networks, an inter-comparison test bed will be established and validation campaigns for selected networks will be conducted.
Evaluations conducted over the past decade have indicated weaknesses in the standard algorithm used by NASA to estimate soil moisture from Advanced Scanning Microwave Radiometer (AMSR) satellite data. This project will assemble and compare all alternatives on a common basis. The first phase of the project focused on implementing the algorithm. Recent work has examined the sensitivity and theoretical basis of the algorithms. Results of the investigation may lead to the selection or development of a new standard soil moisture algorithm. Data products from these satellites and algorithms are being implemented into operational forecast and assessment techniques that will benefit agricultural hydrology and crop yield prediction.