ASCAT-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.
Reference: Liu, X.Z., Wigneron, J.P., Fan, L., Frappart, F., Ciais, P., Baghdadi, N., Zribi, M., Jagdhuber, T., Li, X.J., Wang, M.J., Bai, X.J., & Moisy, C. (2021c). ASCAT IB: A radar-based vegetation optical depth retrieved from the ASCAT scatterometer satellite. Remote Sensing of Environment, 264.