Comparison between Brightness Temperature and Reflectivity to Thickness of Sea-ice

Sea ice is an essential component of the global climate system since it influences and is influenced by changes and variations in the global energy balance and water cycle. In the context of decreasing SIE over the Arctic and an increasing area covered by the seasonal ice, spatial and temporal variations in thin ice especially its thickness are important research questions. The brightness temperature characteristic to thickness is important because it estimates from the brightness temperature. And the verification of the estimated result is also important. However, the observation of thin sea ice is difficult. Therefore, the comparison with other data is important. The reflectivity of visible and near-infrared has a low characteristic in the thin sea ice area. The purpose of this study clarified the brightness temperature characteristic of sea ice, and compared the relations between reflectivity and the brightness temperature of the sea ice. The compared data is a brightness temperature from AMSR-E and reflectivity from MOIDS. The analysis converted the projection of both data into the same polar stereographic. And, the clear regions were chosen from the cloud flag and compared. The analytical result on January 15, 2003 is reported. The pixel of reflectivity 0.2-0.3 of MODIS band 1 was distributed about 80% in brightness temperature of 185-190K. And the pixel of reflectivity 0.2 of MODIS band 2 was distributed about 80% in same brightness temperature. On the other hand, the pixel of reflectivity 0.7 of MODIS band 1 was distributed about 65% in brightness temperature of 240-245K. And the pixel of reflectivity 0.7-0.8 of MODIS band 2 was distributed about 80% in same brightness temperature. The reflectance of visible and near-infrared are low in thin sea-ice. The reflectivity of bands 1 and 2 has concentrated on 0.3 or less in low brightness temperature area. Therefore, it seems very possible that this area is thin region. In general the visible reflectance of the snow is 0.8 or more and near-infrared reflectance is about 0.6 different according to the grain size. The reflectivity of band1 and band2 concentrated on a high value in high brightness temperature area. The snow exists on the sea-ice, and it suggests the existence of thick sea ice in this area. Therefore, the brightness temperature of 18Ghz is low in thin ice, and thought to rise while growing up. Therefore, the brightness temperature of 18Ghz will be low in thin condition, and rise while growing up. * Corresponding author. This is useful to know for communication with the appropriate person in cases with more than one author.