ScatSat-1 Leaf Area Index Product: Models Comparison, Development, and Validation Over Cropland

The leaf area index (LAI) is a crucial parameter that governs the physical and biophysical processes of plant canopies and acts as an input variable in land surface and soil moisture modeling. The ScatSat-1 is the latest microwave Ku-band scatterometer mission of Indian Space Research Organization (ISRO), provides data at a higher temporal and spatial resolution for various applications. Due to its all-weather operational capability, it could be used as an alternative to the optical/IR sensors for the LAI estimation. In the technical literature domain, no testing has been done to estimate the LAI using ScatSat-1 scatterometer data. Therefore, the objective of this study is to retrieve the LAI using the ScatSat-1 backscattering by modifications of two different models viz. water cloud model (WCM) and the recently developed Oveisgharan <italic>et al.</italic> model and compared against the PROBA-V, MODIS, and ground-based LAI products. To assess the performance of these models, coefficient of determination (<inline-formula> <tex-math notation="LaTeX">$R^{2}$ </tex-math></inline-formula>), root-mean-squared error (RMSE) and bias are computed. For Oveisgharan <italic>et al.</italic>, the values of <inline-formula> <tex-math notation="LaTeX">$R^{2}$ </tex-math></inline-formula>, RMSE and bias were obtained as 0.87, 0.57 m²m⁻², and 0.05 m²m⁻² respectively, whereas for WCM model, the values were found as 0.82, 0.67 m²m⁻², and 0.32 m²m⁻² respectively. This investigation showed that the modifications in Oveisgharan <italic>et al.</italic> model provide marginally better results in the retrieval of LAI using ScatSat-1 data than the WCM model. The models’ limitation may be less serious for crop management studies because the majority of crops attains its maturity at LAI values less than 6 m²/m².