Robustness of Vegetation Optical Depth Retrievals Based on L-Band Global Radiometry

Microwave vegetation optical depth (VOD) and soil moisture (SM) can be simultaneously retrieved based on L-band radiometry with polarization information. VOD is indicative of the water content (VWC) because it captures extinction land surface emission. If connectivity to VWC robust, pair VWC-SM observations viable bases for understanding soil-plant-atmosphere relations, providing new perspectives ecosystem science. Simultaneous SM-VOD retrievals are feasible by inverting τ–ω model two independent datasets in dual channel algorithms. However, given correlated satellite vertical horizontal brightness temperatures (TBv TBh), an ill-posed inverse problem arises where TB errors result high uncertainties retrievals. In this study, we apply Degrees-of-Information (DoI) metric propose a Signal-to-Noise Ratio (SNR) assess “retrievability” SMAP TBv-TBh linear dependence. The application these metrics allows determining robust reliable. This necessary step supporting applications ecology hydrology. Results show that regions mainly non-woody have best potential retrievals, though regularization necessary. We then time variations from products reduce impact under-determined inversions: L3-DCA MTDCA, which constrain dynamics without using priori climatology, respectively. Though they both noise, especially differences seasonal amplitude coupling SM at frequencies as outline here.