Global-scale assessment and inter-comparison of recently developed/reprocessed microwave satellite vegetation optical depth products

The vegetation optical depth (VOD), a index retrieved from passive or active microwave remote sensing systems, is related to the intensity of extinction effects within canopy layer. This only marginally impacted by atmosphere, clouds and sun illumination, thus increasingly used for ecological applications at large scales. Newly released VOD products show different abilities in monitoring features, depending on algorithm satellite frequency. sensitive upper layer as frequency increases (from L-, C- X-band), offering capacities monitor seasonal changes leafy and/or woody components, water status aboveground biomass. study evaluated nine recently developed/reprocessed AMSR2, SMOS SMAP space-borne instruments structural features phenology, height For seasonality green (herbaceous foliage), we found that X-VOD products, particularly LPDR-retrieval algorithm, outperformed other regions are not densely vegetated, where they showed higher temporal correlation values with indices (VIs). However, LPDR time series failed detect after rainfall events whereas most could do so, overall daily variations less pronounced X-VOD. Results reprocessed VODCA have almost comparable performance C-VOD correlates better VIs than products. Low L-VOD, new version (V2) SMOS-IC, VIs, similar C-VOD, medium-densely vegetated biomes such savannas (R ~ 0.70) short types. Because L-VOD more non-green components (trunks branches) well-correlated biomass: 0.91) across space between predicted observed both SMOS-IC V2 MT-DCA. when compared forest height, results L-band systematically revealed specific retrieval issues some ecosystems, e.g., boreal regions. It expected these findings can contribute refinements, product enhancements further developing use above-ground biomass, dynamics phenology.