ASCAT IB: A radar-based vegetation optical depth retrieved from the ASCAT scatterometer satellite
FRAPPART, Frédéric
Interactions Sol Plante Atmosphère [UMR ISPA]
Laboratoire d'études en Géophysique et océanographie spatiales [LEGOS]
< Réduire
Interactions Sol Plante Atmosphère [UMR ISPA]
Laboratoire d'études en Géophysique et océanographie spatiales [LEGOS]
Langue
en
Article de revue
Ce document a été publié dans
Remote Sensing of Environment. 2021-10, vol. 264, p. 112587
Elsevier
Résumé en anglais
Vegetation optical depth (VOD), as a microwave-based vegetation index for vegetation water and biomass content, is increasingly used to study the impact of global climate and environmental changes on vegetation. Currently, ...Lire la suite >
Vegetation optical depth (VOD), as a microwave-based vegetation index for vegetation water and biomass content, is increasingly used to study the impact of global climate and environmental changes on vegetation. Currently, VOD is mainly retrieved from passive microwave data and few studies focused on VOD retrievals from active microwave data. The Advanced SCATterometer (ASCAT) provides long-term C-band backscatter data at Vertical-Vertical (VV) polarization. In this study, a new ASCAT INRAE Bordeaux (IB) VOD (hereafter, IB VOD), was developed based on the Water Cloud Model (WCM) coupled with the Ulaby linear model for soil backscattering. The main features of IB VOD are that (i) the ERA5-Land soil moisture (SM) dataset was used as an auxiliary SM dataset in the retrievals, (ii) pixel-based soil model parameters were mapped using Random Forest (RF), and (iii) the vegetation model parameter was calibrated for each day. The IB VOD product was retrieved over Africa during 2015–2019, and its performances were evaluated in space and time by comparing with aboveground biomass (AGB), lidar tree height (TH), normalized difference vegetation index (NDVI), enhanced vegetation index (EVI) and leaf area index (LAI). Results were inter-compared with three other VOD products at the same frequency. In terms of spatial correlation with AGB (R = 0.92) and TH (R = 0.89), IB VOD outperforms the other VOD products, suggesting IB VOD has a strong ability to capture spatial patterns of AGB and TH. By comparing all VOD products against NDVI, EVI and LAI, we found that the highest temporal correlation with NDVI (EVI, LAI) was obtained with IB VOD over 29.94% (36.65%, 30.19%) of the study region. Considering all three vegetations indices, highest temporal correlation values with IB VOD could be particularly noted for deciduous broadleaf forests, woody savannas and savannas.< Réduire
Mots clés en anglais
VOD
ASCAT
Active microwave
Africa
Biomass
Tree height
NDVI
EVI
LAI
Origine
Importé de halUnités de recherche