Location: Hydrology and Remote Sensing LaboratoryTitle: Retrieving surface soil moisture from GRACE satellite gravity data
|SADEGHI, M. - University Of Minnesota|
|GAO, L. - University Of Minnesota|
|EBTENAJ, A - University Of Minnesota|
|WIGNERON, J. - Bordeaux University|
|REAGER, J.T. - Jet Propulsion Laboratory|
Submitted to: Journal of Hydrology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/20/2020
Publication Date: 5/10/2020
Citation: Sadeghi, M., Gao, L., Ebtenaj, A., Wigneron, J., Reager, J., Crow, W.T. 2020. Retrieving surface soil moisture from GRACE satellite gravity data. Journal of Hydrology. https://doi.org/10.1016/j.jhydrol.2020.124717.
Interpretive Summary: Satellite surface soil moisture estimates derived from microwave sensors are used for a variety of agricultural applications including irrigation scheduling, yield forecasting and drought monitoring. However, these estimates have severe limitations during high biomass conditions typically present in agricultural landscapes during later periods of the crop growing season. To address this shortcoming, this paper describes a new gravity remote sensing technique to recover monthly surface soil moisture estimates. Since these gravity-based estimates can be obtained even in the presence of dense crop canopy cover, they provide a useful correction for microwave-based soil moisture estimates acquired during high biomass periods. This paper derives the gravity-based soil moisture retrieval algorithm and compares it to existing ground- and microwave-based soil moisture products. Results provide a compelling proof-of-concept for the approach and will eventually be used by agricultural drought monitors to improve our ability to track soil water availability through the entirety of the crop growing season.
Technical Abstract: Passive microwave radiometry from space through missions such as the Soil Moisture and Ocean Salinity (SMOS) and Soil Moisture Active Passive (SMAP) satellites is the most reliable means for mapping global surface soil moisture (SSM). Nonetheless, microwave SSM is uncertain over densely vegetated surfaces or areas with high radio frequency interference. This paper presents a new approach to remote sensing of global SSM based on the terrestrial water storage anomaly (TWSA) data from the Gravity Recovery and Climate Experiment (GRACE) satellite with a longer historical period than the most existing microwave satellites. This approach rests on a physically based, yet parsimonious, model based on the Richards’ equation and the assumption that the TWSA temporal rate of change (dS/dt) approximates the land surface net water flux (NWF) as the surface boundary condition. The GRACE-based SSM is found to be in a reasonable agreement with in-situ data and highly correlated with the SMAP and SMOS retrievals, especially over wet regions where the assumption of NWF ˜ dS/dt holds valid.