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Lee and Chi (2004) have reported maximum 30mm subsidence that have occurred on Hwaong reclaimed mudflat, west coast of Korea, during September to October 2003 by Radarsat-1 DInSAR analysis. DInSAR observation of land subsidence, however, should consider the effect of microwave penetration into soil which occurs in the same direction with subsidence. To discriminate the subsidence and microwave penetration into a drying mudflat, we performed a laboratory experiment with a polarimetric scatterometer (PolScat). The PolScat is composed of 5.0-5.6GHz dual-polarization square horn antenna and Agilent 8753ES vector network analyzer. Fully polarimetric data were acquired from the saturated mud state (gravimetric soil water content of 60%) to dry mud state (5%) on a sample (2m×2m×0.2m) for six weeks. Among the total phase change of -155° (17mm vertical shift), the initial -105° was due to 11mm subsidence and the later -50° was due to 6mm microwave penetration into dry mud. It was shown that the microwave penetration is not a negligible parameter in conjunction with soil moisture and subsidence, and can be compensated for using a PolScat observation.

We have analyzed the variation of radar backscattering coefficient of natural mudflat, when it is above the sea level and subject to structural change and evaporation, by using a set of Radarsat-1 SAR images, tidal height record, evaporation record, and polarimetric scatterometer experiments on drying mud. The 15 Radarsat-1 SAR data, obtained one in 2001 and the others from 2003 to 2004 were all in S5 ascending mode taken at around 18:30pm local time which is an ideal time for evaluating daytime evaporation effect considering 12.42-hour tidal cycle. The exposure time of mudflat is calculated by combining the tidal height record and a DEM of mudflat constructed by the waterline extraction method. We then defined the 'evaporation time' by multiplying the exposure time with the normalized evaporation index, which are compared with SAR backscattering coefficient. The result was not a monotonic decrease of backscattering coefficient with the evaporation time but a complex variation of M shaped (increase-decrease-increase- decrease) sequence due to structural and moisture change of drying mud. In the first few hours of exposure, the remnant water pools act as specular reflectors reducing roughness of the surface and the backscattering was very low. As the water pool dries out the backscattering increases due to roughness increase. After the water pools have vanished, the backscattering decreases as evaporation goes on due to the decreasing dielectric constant. Another backscattering jump follows when the mud cracks begin to appear until they fully develop. After that the tidal mudflat is structurally stabilized and the backscattering decreases monotonically. This variation was confirmed by Radarsat-1 SAR images.

We have compared Kompsat-1 EOC images (6.6 m resolution, panchromatic) of the Arctic and Antarctic sea ice with SSM/I sea ice concentration (SIC). EOC images were obtained from 10 orbits (624 scenes) across the Arctic sea ice edges from July to August and 11 orbits (676 scenes) across the Antarctic continental edges from September to November, all in year 2005. By applying supervised classification and visual identification to about 12% usable images out of the total scenes, we have classified various sea ice types such as multi-year ice and first- year ice (M+F), Young ice (Y), and New ice (N). EOC SIC were derived and compared with SSMI SIC calculated by NASA Team Algorithm (NTA). In summertime of the Arctic, the correlation coefficient between EOC SIC (M+F+Y+N) and SSM/I SIC were low (0.671) due to rapid temporal and spatial variation of sea ice. For springtime in the Antarctic, EOC SIC (M+F+Y, excluding N) and SSM/I SIC have shown the highest correlation coefficient (0.873). We have concluded that the NTA- derived SSM/I SIC includes Y as well as M+F, but not N.