A phase signature for detecting subsurface moisture using polarimetric L-band SAR: example of the Pyla dune-France

We investigate the penetration capabilities of L-band microwaves for the mapping of subsurface moisture. Our experimental site is the Pyla dune, a bare sandy area allowing high signal penetration and presenting large subsurface wet structures (paleosoils) at varying depths. We established that a phase signal is correlated to the buried and wet paleosoils: a phase difference between HH and VV channels reaching 25° was clearly observed on L-band airborne SAR data. This phase signature was confirmed by fieldwork measurements and fits the semi-empirical model proposed by Oh et al.