Advice on using the MMAB Ice concentrations

NOAA/NWS Disclaimer

Advice on Interpreting the MMAB Ice concentrations

The image itself displays the ice concentration in intervals. Special colors are pale purple ('weather'), darker purple (no data), gray (too much land near the cell for reliable ice concentrations), and black (land). Red indicates low concentrations (16 to 28 percent), while blues indicate high ice concentrations (over 85%). The color bar on the web page gives the full description of the relation.

The NASA Team algorithm is used to estimate the ice concentrations. The algorithm as implemented by MMAB is described in a technical note which is available in print as well as on-line. The algorithm works by comparing the observations to signatures typical of different ice types. Things other than ice can give an ice signature. This includes high seas and high precipitation rates. There is a filter which removes most of this contamination from the ice field, but it is not always effective. Most of the time, the false ice reports are for low concentration. This occurred on 8 January 1997, for example, at a time when Russ Page, in the Anchorage WSFO, tells me there were 60 knot winds in the Bering Sea. In the summer, the layers and puddles of water which can accumulate on the surface of the ice floes mislead the algorithm in to underestimating the total ice concentration.

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