REDUCTION OF WEATHER EFFECTS IN THE CALCULATION OF SEA-ICE CONCENTRATION WITH THE DMSP SSM I/

A problem in mapping the polar sea-ice covers in both hemispheres has been the sporadic false indication of sea ice over the open ocean and at the ice edge. These spurious sea-ice concentrations result from var iations in sea-surface roughening by surface winds, atmospheric water vapor and both precipitating and non-precipitating liquid water. This problem was addressed for sea-ice concentrations derived from the Nimb us-7 scanning multi-channel microwave radiometer (SMMR) data through t he development of a weather filter based on spectral information from the 18.0 and 37.0 GHz vertical polarization SMMR channels. Application of a similar filter for use with sea-ice concentration maps derived w ith the special-sensor microwave imager (SSM/I) sensor is less success ful. This results from the position of the 19.35 GHz SSM/I channels, w hich are closer to the center of the 22.2 GHz atmospheric water-vapor line than are the SMMR 18.0 GHz channels. Thus, the SSM/I 19.35 GHz ch annels are more sensitive to changes in atmospheric water vapor, which results in greater contamination problems. An additional filter had b een developed, based on a combination of the 19.35 and 22.2 GHz SSM/I channels. Examples of the effectiveness of the new filter are presente d and limitations are discussed.