ALOS-2 and Sentinel-1 use for retrieving soil moisture over cereal fields in semi-arid area: the Kairouan plain – central Tunisia

Abstract

In the present study, we evaluate the potential of multi-incidence L-band and C-band data to retrieve soil moisture. In -situ measurements were acquired during satellite acquisitions over cereal fields in the Kairouan plain in central Tunisia (semi-arid area). Analysing radar data, L-band Advanced Land Observing Satellite-2 multi-incidence data (28°, 32.5° and 36°) in HH (L-HH) and HV (L-HV) polarizations and C-band like-polarization Sentinel-1data, with an incidence angle of approximately 39°, (C-VV) are strongly impacted by soil roughness. In addition, results highlight the sensitivity of L-band data to soil moisture in dense cover class where Normalized Vegetation Difference Index (NDVI) values are higher than 0.6. Two options of Water Cloud Model (WCM) were used (with and without the integration of soil-vegetation interaction component) to simulate radar signal over cereal fields. Each option of WCM was coupled to the best performance bare soil backscattering models. By inverting WCM, results underline the important contribution of soil-vegetation interaction component to estimate soil moisture with L-HV data compared to a neglected impact on C-band data inversion accuracy and stable accuracy in L-HH.