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The following information about CD-ROMs is retained for historic purposes.
The NASA Nimbus-7 SMMR Team Algorithm (Cavalieri et al. 1984, Gloersen and Cavalieri 1986) with revised tie points (Gloersen et al. 1992, p. 27) was used to calculate ice concentrations from the SMMR brightness temperatures. Derived ice concentration grids were stored separately for the northbound and southbound (ascending and descending) orbital nodes. This was done in view of the rapid changes known to take place in the polar ice covers, and because of the nonlinear nature of the sea ice algorithm. To be consistent with the daily-averaged brightness temperatures stored in this 12-volume set of CD-ROMs, the northbound and southbound (ascending and descending) ice concentration data were averaged to produce a daily-averaged ice concentration map for each SMMR data day (the SMMR sensor operated on alternate days to conserve power). Be cautioned that producing ice concentrations from the daily-averaged brightness temperatures may yield slightly different results than the ice concentration maps presented in the published atlas.