Validation results of ADEOS-II/GLI snow products

Two types of snow grain sizes and mass concentration of snow impurities were made with ADEOS-II/GLI data from April to October in 2004. In general, both of retrieved snow parameters took lower values in the high latitudinal areas and low temperature areas. For the calibration of the sensor and the validation of the algorithms, several field campaigns were carried out in Alaska and eastern Hokkaido, Japan. Based on snow pit work, the retrieved snow grain size using the channel combination at 0.46μm and 0.865μm agreed with the measured values averaged over a snow layers from surface to several-cm depth. However, the satellite-derived grain sizes from 1.64μm-channel, which is expected to be sensitive to surface snow grain size, were generally smaller than those measured at the ground. Possible reason of this underestimate is sun crust (thin ice layer created by solar radiation under clear sky) at snow surface, which increases the snow reflectance by additional specular reflection, in the case of granular (wet) snow during melting reason. The mass concentration of snow impurities retrieved from the satellite data was lower than the measured one. This is because snow impurities are assumed to be soot in the remote sensing algorithm, whereas the main composition of in situ measured impurities was generally found to be mineral dust in our sites.