Inverting soil moisture information from satellite radar altimetery backscatter
Event: 2016 Ocean Surface Topography Science Team Meeting
Session: Science III: Two decades of continental water's survey from satellite altimetry - From nadir low-resolution mode to SAR altimetry, new perspectives for hydrology
Presentation type: Type Oral
Satellite radar altimeters, which have been designed to monitor changes of sea surface height over the ocean, also provide backscatter measurement over land surfaces. The backscatter from Ku- and C-/S-Band over land is provided at high resolution (~300m) at 10 or 35 day intervals for Jason-2 and Envisat, respectively, and related to surface features, such as roughness, vegetation or soil moisture.
Here, we present an inversion framework that allows to retrieve soil moisture information from along-track Jason-2 and Envisat satellite altimetry backscatter observations. There are three main steps to our approach: (i) computing time-invariant spatial patterns (base-functions) by applying principal component analysis (PCA) to simulated soil moisture from an available land surface model. (ii) Estimating time-variable soil moisture evolution by fitting these base functions of (i) to the along-track retracked backscatter coefficients in a least squares sense. (iii) Combining the estimated time-variable amplitudes and the pre-computed base-functions to reconstruct altimetry based soil moisture information.
We validated our approach over the arid and semi-arid regions of Western Australia against an available local high resolution (0.05°x0.05°) model (AWRA-L), as well as against very fine resolved (200m) model data from the Wasim model over Western Germany.