The potential for interpreting total and multiyear ice concentrations in SSM/I 85.5 GHz imagery

Abstract The 85.5 GHz vertically and horizontally polarized channels of the Special Sensor Microwave Imagers (SSM/I) aboard the Defense Meteorological Satellite Program (DMSP) spacecraft offer the potential to map sea ice with a spatial resolution of 12.5 km, a factor of two improvement over the popular National Aeronautics and Space Administration (NASA) Team algorithm, but with the limitation of increased atmospheric influence on the sea ice signal. Application of an algorithm for estimating total ice concentration from 85.5 GHz data, which exploits the large polarization for open water versus the small polarization for most ice types, reveals agreement with the NASA Team algorithm typically within a standard deviation of ± 3% for nearly cloud free winter conditions. The uncertainty increases to a standard deviation of ± 6% for cloudy winter conditions. In winter, volume scattering from multiyear ice has a noticeable impact on the 85.5 GHz brightness temperatures. By employing a polarization corrected temperature variable previously defined to isolate precipitation in mid-latitude DMSP imagery, it is possible to exploit the large differences in 85.5 GHz emissivity between first year and multiyear ice to interpret an 85.5 GHz image in terms of both total ice and multiyear ice concentration. Preliminary results, for nearly cloud free winter conditions, reveal agreement between these interpretations and the NASA Team algorithm to within a standard deviation of ± 6%, with slightly better agreement at low multiyear ice concentration.