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Section 2.3 of the SMMR Atlas describes the SMMR Team sea ice algorithm (Gloersen et al. 1984; Cavalieri et al. 1984; Gloersen and Cavalieri 1986), which is based on " . . . the radiative transfer equation, the contrasting emission characteristics of ice and ocean, and the assumption that the observed brightness temperature can be linearly related to the brightness temperatures of three surface types (open ocean and two ice types, the latter being first-year and multiyear ice in the Arctic and less specific "Type A" and "Type B" ice in the Antarctic). In order to reduce the effect of physical temperature, the ice-concentration formulations are based upon the polarization and spectral gradient ratio introduced in Section 2.1 (of the SMMR Atlas), rather than directly on the brightness temperatures themselves." (Gloersen et al. 1992, p. 25) Algorithm tie points are shown in Table D.1, below. Please refer to sec. 2.3 of Gloersen et al. (1992) for more detailed information.