Location: Hydrology and Remote Sensing LaboratoryTitle: Evaluation of the tau-omega model for passive microwave soil moisture retrieval using SMAPEx data sets
|GAO, Y. - Monash University|
|WALKER, J. - Monash University|
|YE, N. - Monash University|
|PANCIERA, R. - Melbourne University|
|MONERRIS, A. - Monash University|
|RYU, D. - Melbourne University|
|RUDIGER, C. - Monash University|
Submitted to: IEEE Journal of Selected Topics in Applied Remote Sensing
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/3/2018
Publication Date: 3/1/2018
Citation: Gao, Y., Walker, J., Ye, N., Panciera, R., Monerris, A., Ryu, D., Rudiger, C., Jackson, T.J. 2018. Evaluation of the tau-omega model for passive microwave soil moisture retrieval using SMAPEx data sets. IEEE Journal of Selected Topics in Applied Remote Sensing. 11(3):1-10.
Interpretive Summary: The key parameters used by the essential model used in microwave remote sensing of land, the tau-omega model, were assessed using airborne L-band passive microwave observations and ground sampling information collected in dedicated field experiments conducted in Australia. The evaluation of the parameters used by the Soil Moisture Active Passive (SMAP) satellite showed an underestimation of soil moisture in general, while the parameters calibrated from an earlier campaign yielded an overestimation bias. Results of this study suggest that the values of the parameter that SMAP uses to represent surface roughness are too low for South-eastern Australian conditions. The new values derived for both surface roughness and vegetation will be incorporated into an algorithm for the study domain and potentially similar land covers across the globe.
Technical Abstract: The parameters used for passive soil moisture retrieval algorithms reported in the literature encompass a wide range, leading to a large uncertainty in the applicability of those values. This paper presents an evaluation of the proposed parameterizations of the tau-omega model from 1) SMAP ATBD for global condition and 2) calibrated parameters from NAFE’05 (the National Airborne Field Experiment) for Australian conditions, with special focus on the vegetation parameter b and roughness parameter HR. This study uses airborne L-band data and field observations from the Soil Moisture Active Passive Experiments (SMAPEx) conducted in south-eastern Australia. Results show that the accuracy with the proposed parameterizations from SMAP ATBD was satisfactory at 100-m spatial resolution for maize (0.06 m3/m3) and pasture (0.07 m3/m3), while it reached to 0.18 m3/m3 for wheat. Calibrated parameters from the NAFE’05 did not provide better results, with the accuracy of wheat degrading to 0.28 m3/m3. After a comprehensive site-specific calibration and validation at 100-m spatial resolution, this result was improved to 0.11 m3/m3. Further calibration and validation were performed at 1-km resolution against intensive ground sampling and at 3-km against in situ monitoring stations. Results showed an accuracy over grassland and cropland of 0.05 m3/m3 and 0.06 m3/m3 respectively. This study also suggests that the parameters from SMAP ATBD show an underestimation of soil moisture, with the roughness parameter HR being too low for Australian condition. Therefore, a new set of b and HR parameters for 10 different land cover types was proposed in this study.