|Hsu, Ann - USDA-ARS CONTRACTOR|
Submitted to: IEEE Transactions on Geoscience and Remote Sensing
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: May 1, 2001
Publication Date: June 1, 2001
Interpretive Summary: Current and near future satellite earth observing systems, while not ideal for soil moisture measurement, can provide information for some conditions. Soil moisture retrieval algorithms for these systems have been proposed but have not rigorously evaluated and there are few data sets available for thi purpose. This is a challenging problem because the area observed by the satellite is quite large. An experiment, Southern Great Plains 1999, was conducted to address this gap in knowledge. Information retrieved using the existing passive microwave satellite instruments, in particular the Tropica Rainfall Mapping Mission, was compared to ground observations of soil moisture. Theoretical models were used as the basis of a soil moisture mapping technique, which was verified using the observations. As opposed to previous studies, soil moisture maps were derived for the entire region to demonstrate the capability of the technique. The analysis of the satellite data and the resulting maps showed that consistent satellite based soil moisture retrieval at coarse resolutions is possible on a regional basis. T results of the study provide the fundamental justification for both the implementation of this technique over larger regions such as North America and for the development of improved satellite observing systems. These products will impact regional assessments and will improve the accuracy of weather and climate forecasts, which could have significant impacts on hydrologic and agricultural management and decision making.
Technical Abstract: Satellite data collected by the TRMM Microwave Imager (TMI) and the Special Sensor Microwave/Imager (SSM/I) were compared to soil moisture observations as part of the Southern Great Plains (SGP) 1999 Experiment. SGP99 was conducted to address significant gaps in the knowledge base on the microwave remote sensing of soil moisture. Satellite, aircraft and ground based data collection were conducted between July 8th and July 20th during which an excellent sequence of meteorological conditions occurred. Cross calibration of the SSM/I data to the same TMI channels showed nearly identical brightness temperatures. 19 GHz SSM/I data and soil moisture relationships were similar to those observed in previous experiments in this region. Studies comparing the SSM/I and TMI channels revealed that only study areas with adequate spatial domains should be used for soil moisture validation. Analyses of the TMI 10 GHz data provide new information on potential improvements that this channel can provide for soil moisture estimation. Soil moisture maps of the region were derived for dates of coverage.