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The NASA Team algorithm uses the 19V, 19H, and 37V channels to determine ice concentration using two ratios: PR generally distinguishe s between open water and ice, with open water having higher PR values. GR generally distinguishes between two ice types (multiyear and first-year ice in the Arctic, with higher GR values corresponding to first-year ice). Two weather filters are employed to eliminate spurious ice retrievals over open water due to wind, cloud liquid water, water vapor and other atmosphe ric interference. The filters are based on threshold values of GR(37V/19V) and GR(22V/19V). The use of brightness temperature ratios minimizes the effects of surface temperature on the ice concentration retrieval. However , the algorithm does have drawbacks. The use of the 19 GHz channel reduces the ice edge resolution because the 19 GHz channel has a much larger footp rint (FOV) than the 37 GHz (70 x 45 km versus 38 x 30 km). Also, the use of the 19H channel is particularly sensitive to wind effects over open water, although the weather filters are generally effective at removing these effects. A crucial drawback of the NASA Team algorithm in marginal ice zone areas is that it often dramatically underestimates thin ice concentra tions. The algorithm tends to see thin ice as a mixture of thicker ice and open water instead of widespread thin ice. Cavalieri, D.J., P. Gloersen, and W.J. Campbell, 1984. "Determination of sea ice parameters with the NIMBUS 7 scanning multichannel microwave radiometer", J. Geophys. Res., 89, 5355 - 5369. Comiso, J.C., D.J. Cavalieri, C.L. Parkinson, and P. Gloersen, 1997. "Pas sive microwave algorithms for sea ice concentration: A comparison of two techni ques", Remote Sens. Env., 60, 357-384. Gloersen, P., and D.J. Cavalieri, 1986. "Reduction of weather effects in the calculation of sea ice concentration from microw ave radiances", J. Geophys. Res., 91, 3913-3919.


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