Thawing processes during Siberian spring observed by ERS scatterometer and SAR

From multi-temporal radar backscatter measurements obtained from the ERS scatterometers at various incidence angles, the state (frozen/thawed) of the upper layer of the soil in Arctic to temperate climate regions is monitored. Sequences of SAR images are compared to the temporal signal of the scatterometer. In spring, the data of both instruments show distinct variations which can be attributed to thawing and freezing soils. From tracking a warm event in spring 1995, a high sensitivity of the radar return to the state of the snow is observed. The radar signature of dry-snow and firn varies on the same order as frozen and thawed soils (approx. 4 dB) whereas variations associated with the day-night temperature difference are not detected