Understanding radar backscatter sensitivity to vegetation water dynamics: Sub-daily variations in ground-based experiments

Observing vegetation water dynamics from space offers insights into plant-water relations and water and carbon fluxes across ecosystems at local to global scales. A promising technique to observe water in the vegetation layer is radar, an active form of microwave remote sensing. Interactions between microwaves and vegetation material depend on dielectric properties of the vegetation tissue, which are a function of water content. The research presented within this thesis aims to extend our physical understanding of the relationship between vegetation water dynamics and radar backscatter. The particular focus was on sub-daily dynamics, motivated by the dynamic nature of plantwater interactions and developments in the availability of sub-daily spaceborne radar observations. Moreover, we examined the effect of vertical water dynamics inside the vegetation layer on backscatter, which is relevant for better understandingwhich parts of the vegetation layer control the signal. To limit complexity, we focused on homogeneous corn fields. During ground-based experimental campaigns, we collected scatterometer data in vertical (VV), horizontal (HH) and cross (VH and HV) polarizations, and extensive measurements of water dynamics from these fields. These datasets were analyzed using statistical analyses and electromagnetic models.