The following is a description of the global seasonal Snow Classification System and data set presented in the paper: Sturm, M., J. Holmgren, and G. Liston. 1995. A Seasonal Snow Cover Classification System for Local to Global Applications. Journal of Climate. 8(5):1261-83. Based on the physical properties of snow (depth, density, thermal conductivity, number of layers, degree of wetting, etc.), Sturm et al. have divided the world's seasonal snow covers into six classes, plus water and glacier ice. Each snow cover class is defined by its physical properties, and then is empirically related to climate using three variables (precipitation, wind, and air temperature). Vegetation is used as a proxy for wind data: tall vegetation indicates low wind, short vegetation indicates high wind. Details are available in the above paper. A companion paper listing physical and thermal attributes for each class of snow is in preparation, but preliminary snow cover attribute values can be obtained through correspondence with the authors (addresses given below). The classes and the integer value assigned to each class are: water = 0 tundra snow = 1 taiga snow = 2 maritime snow = 3 ephemeral snow = 4 prairie snow = 5 alpine snow = 6 ice = 7 This data set was developed and tested for the Northern Hemisphere. Results for the Southern Hemisphere are untested and have not been evaluated (it is known that the Southern Hemisphere suffers from a reduced density of meteorological data which may well have influenced the quality of the snow classification in that area). Also note that in the data set much of Antarctica is inappropriately defined as water (the earth-surface classification data set used by Sturm et al. did not extend that far south). A 0.5 by 0.5 degree land-sea mask could be used to set the Antarctic region to the ice = 7 classification if this region is of interest.* The original snow classification data are global in coverage and are formatted into an array of integers, 720 columns by 360 rows. Each of the values in the array represent the classification of a 0.5 degree latitude by 0.5 degree longitude cell. NSIDC has re-gridded these data into two EASE-Grid formats: an azimuthal equal area projection for the Northern Hemisphere (nl_sclass) and a cylindrical equal area projection for global coverage (ml_sclass). Images of the data were also created for demonstration purposes (sc_nhem.gif and sc_global.gif). The following people are available to answer questions regarding use of the snow classification data set: Matthew Sturm, Ph.D. USA CRREL-Alaska P.O. Box 35170 Ft. Wainwright, Alaska 99703-0170 907-353-5149 msturm@crrel41.crrel.usace.army.mil Glen E. Liston, Ph.D. Department of Atmospheric Science Colorado State University Fort Collins, Colorado 80523 970-491-7473 liston@tachu.atmos.colostate.edu *9/13/01 NSIDC has created a land/ocean mask from the original (updated) Global Ecosystem map (http://cdiac.esd.ornl.gov/ndps/ndp017.html) used in the derivation of the snow classification. The mask may be used to set the land mass of Antarctica to ice, as described above, altering the data set as submitted. Furthermore, NSIDC has created a new snow classification map, in which Antarctica was coded as ice, as described above, with the remainder of the snow classification map unaltered.