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Title: Evaluation of dielectric mixing models for microwave soil moisture retrieval using data from the Combined Radar/Radiometer (ComRAD) ground-based SMAP simulator

Author
item SRIVASTAVA, P.K. - National Aeronautics And Space Administration (NASA)
item O'NEILL, P.E. - National Aeronautics And Space Administration (NASA)
item Cosh, Michael
item LANG, R.H. - National Aeronautics And Space Administration (NASA)
item JOSEPH, A.T. - National Aeronautics And Space Administration (NASA)

Submitted to: IEEE Journal of Selected Topics in Applied Earth Observations and Remote Sensing
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/15/2014
Publication Date: 12/30/2014
Citation: Srivastava, P., O'Neill, P., Cosh, M.H., Lang, R., Joseph, A. 2014. Evaluation of dielectric mixing models for microwave soil moisture retrieval using data from the Combined Radar/Radiometer (ComRAD) ground-based SMAP simulator. IEEE Journal of Selected Topics in Applied Earth Observations and Remote Sensing. 99:1-10. DOI: 10.1109/JSTARS.2014.2372031.

Interpretive Summary: Soil moisture remote sensing relies upon algorithms for relating microwave brightness temperature measurements to ground based data sets. In this study, a truck mounted L-band instrument which mimics the measurements of the NASA Soil Moisture Active Passive mission instrument was deployed over corn and soybean fields in Beltsville, MD in the summer of 2012 to test four different algorithms for soil moisture estimation. A comparison of these algorithms was conducted and the error statistics were calculated. This information will be used by current and future satellite missions to determine the optimal method for soil moisture estimation from remote sensing signals.

Technical Abstract: Soil moisture measurements are required to improve our understanding of hydrological processes, ecosystem functions, and linkages between the Earth’s water, energy, and carbon cycles. The efficient retrieval of soil moisture depends on various factors in which soil dielectric mixing models are considered to be an important factor. Although a number of soil dielectric mixing models have been developed, testing these models for soil moisture retrieval has still not been fully explored, especially with detailed measurements from ground-based microwave sensors. The main objective of this work focuses on testing different dielectric models for soil moisture retrieval using the Combined Radar/Radiometer (ComRAD) ground-based L-band simulator system which serves as a simulator for the instruments on NASA’s Soil Moisture Active Passive (SMAP) mission scheduled for launch in November 2014. Although there are currently a number of dielectric models available for soil moisture retrieval, in this study four dielectric models-- Mironov, Dobson, Wang & Schmugge, and Hallikainen -- were tested for soil moisture retrieval using the Single Channel Algorithm at H polarization (SCA-H) version of the tau-omega retrieval model. A summer field experiment was conducted in 2012 at a United States Department of Agriculture (USDA) test site near NASA Goddard Space Flight Center. Validation samples of surface soil moisture were collected using theta probes and in situ sensors When comparing the microwave-retrieved soil moisture to the measured soil moisture, the highest performance statistics combination in terms of high correlation (r), low Root Mean Square Error (RMSE), and least bias has been obtained with SCA-H using the Mironov dielectric model (r=0.79; bias=0.01) followed by Dobson (r=0.76;bias=-0.01), Wang & Schmugge (r=0.79; bias=0.02) and Hallikainen (r=0.76; bias=0.04). Although the performance of the four dielectric models is relatively comparable, this analysis indicates that the Mironov dielectric model is promising for passive-only microwave soil moisture retrieval and could be a useful choice for SMAP satellite soil moisture retrieval.