Snow impurities / Snow grain size (865nm ch.) / Snow grain size (1.64um ch.) / Snow surface temperature products (Ver.2) were released to the public on November 1, 2004. Current status of product validation and future plans are described below together with known problems of the current version.

There are some changes made for Ver.2 products as follows.

• Two new parameters are added which are both representing the physical properties of snow surface.
  • Snow grain size (1.64um channel)
  • Snow surface temperature
• High density vegetation areas at which the retrieval of snow physical parameters tend to include significant artifacts are eliminated from the analysis. (But the effect of vegetation on the retrieval accuracy still seems to remain in Ver.2 product.)

Current accuracy of the Ver.2 products (200% for snow impurities, 75% for snow grain size (865nm ch.), and 400% for snow grain size (1.64um ch.)) are estimated based upon the results of ground observations having been conducted at snow fields in Eastern Hokkaido, Japan and in Alaskan tundra near Barrow since 2002. The estimated accuracy for snow surface temperature (5K) was derived from the comparison with MODIS IST products (MOD29E1D). Due to the lack of sufficient truth data the accuracy of snow grain size and impurities products is still preliminary and will be re-evaluated in coming version-up processes of the GLI snow algorithms (Ver.3 in 2005 and later versions. See tentative future plan.). Known concerns decreasing the Ver.2 products' accuracy are sub-pixel contamination of the following surfaces;

• Ocean area with low sea ice concentration
• Land and sea ice area with shallow snow
• Vegetated area