Sea-ice concentration retrieval in the Antarctic based on the SSM/I 85.5 GHz polarization
Abstract:Using data from the 85 GHz channels of the Special Sensor Microwave/Imager (SSM/I) allows a resolution improvement by at least a factor of four compared to the other channels. Consequently, higher-resolution sea-ice concentration data can be obtained which in turn can be used to improve the results of numerical weather-prediction (NWP) and global circulation models. The proposed new sea-ice concentration retrieval algorithm (SEA LION algorithm) uses the polarization at 85 GHz (P). Emission from atmospheric water and scattering at the wind-roughened sea surface (weather effect) decrease P and cause an overestimation of the sea-ice concentration. We quantify the weather effect with a radiative transfer model and atmospheric data obtained from NWP models and the other SSM/I channels, and correct P for this effect. Tie points of open water and sea ice are determined for each month separately from daily gridded 85 GHz SSM/I brightness temperatures. Sea-ice concentrations are calculated with the new algorithm for the entire Southern Ocean for each day of the period 1992–98 with a spatial resolution of 12.5 × 12.5 km2. Comparisons of these ice concentrations with Operational Linescan System visible images reveal convincing results concerning the monitoring of coastal polynyas and the break-up of the pack ice in spring. SEA LION sea-ice extents and areas, and comparisons between SEA LION sea-ice concentrations and ship observations, agree with those obtained by the NASA Team and the Bootstrap algorithms.
Document Type: Research Article
Publication date: January 1, 2001
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