Abstract of PhD Thesis

Active Microwave Remote Sensing of Soil Moisture

Brian Barrett, University College Cork (2011)

The amount of water stored in the soil is a key parameter for the energy and mass fluxes at the land surface and is of fundamental importance to many agricultural, meteorological, biological and biogeochemical processes. The work presented in this thesis investigates the use of spaceborne Synthetic Aperture Radar (SAR) data to characterise near-surface soil moisture content at both the field and catchment scale over agricultural areas in Ireland. In particular, the research assesses 1) the inter-annual and seasonal relationship between ASAR Wide Swath Mode (WSM) backscatter and variations in surface soil moisture over grasslands, 2) the applicability of backscatter intensity change (Δσ0) and interferometric coherence (γ) thresholding in facilitating soil moisture change detection in agricultural fields, and 3) whether C- and L-band Differential Interferometric SAR (DInSAR) can be used for soil moisture change detection. Results highlight the value of merging complementary information, derived from both the intensity and phase of the backscattered signal, to improve the reliability of the relationship between radar backscatter and soil moisture content and also support the hypothesis that a soil moisture phase contribution exists within differential interferograms covering agricultural areas, which may have implications for standard DInSAR analysis