Radar measurement of soil moisture: From professor Fawwaz Ulaby´s pioneering works in the early 1970s to its current status

This paper reviews the progress in the radar measurement of soil moisture. At first the pioneering works done by Ulaby [1] in the early 1970s for radar measurements for bare and vegetated surfaces are revisited. Then the development of polarimetric scattering models and inversion algorithms for retrieving soil moisture from polarimetric radar measurements are reviewed. This review especially focuses on retrieving both surface roughness and soil moisture from polarimetric radar measurements. Finally, this paper presents the progress and problems on radar measurement of soil moisture for a vegetated rough surface.