Detecting Changes in Surface Soil Moisture Content using Differential SAR Interferometry (DInSAR)

The feasibility of measuring changes in surface soil moisture content with differential interferometric SAR (DInSAR) has received little attention in comparison to other active microwave techniques. In this study, multi-polarisation Cand L-band DInSAR is explored as a potential tool for the measurement of changes in surface soil moisture in agricultural areas. Using ten ascending Phased Array L-band Synthetic Aperture Radar (PALSAR) scenes acquired by the Japanese Advanced Land Observing Satellite (ALOS) satellite and twelve descending Advanced Synthetic Aperture Radar (ASAR) scenes acquired by the European ENVISAT satellite between July 2007 and November 2009, a series of 27 differential interferograms covering a common study area over southern Ireland were generated to investigate whether small-scale changes in phase are linked to measured soil moisture changes. Comparisons of observed mean surface displacement and in-situ mean soil moisture change show that C-band HV polarisation pairs displayed the highest correlation coefficients over both the barley (r = 0.51, p = 0.04) and potato crop (r = 0.81, p = 0.003) covered fields. Current results support the hypothesis that a soil moisture phase contribution exists within differential interferograms covering agricultural areas.