Skip to Main content Skip to Navigation
Journal articles

ASCAT IB: A radar-based vegetation optical depth retrieved from the ASCAT scatterometer satellite

Abstract : 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.
Document type :
Journal articles
Complete list of metadata

https://hal.inrae.fr/hal-03318149
Contributor : Nicolas Baghdadi <>
Submitted on : Monday, August 9, 2021 - 1:35:47 PM
Last modification on : Wednesday, September 22, 2021 - 10:17:56 AM

Identifiers

Citation

Xiangzhuo Liu, Jean-Pierre Wigneron, Lei Fan, Frédéric Frappart, Philippe Ciais, et al.. ASCAT IB: A radar-based vegetation optical depth retrieved from the ASCAT scatterometer satellite. Remote Sensing of Environment, Elsevier, 2021, 264, pp.112587. ⟨10.1016/j.rse.2021.112587⟩. ⟨hal-03318149⟩

Share

Metrics

Record views

81