New passive microwave remote sensing technique for sea ice in the Sea of Okhotsk using 85-GHz channel of DMSP SSM/I

A new sea ice classifying algorithm has been developed, based on aircraft measurements of the ice in Lake Saroma and in the Sea of Okhotsk by using a NASDA-developed Airborne Microwave Radiometer (AMR). This algorithm uses a parameter related to the 89-GHz channel of the AMR, which has the finer resolution, than the other channels. This high spatial resolution algorithm was applied to the Special Sensor Microwave/Imager (SSM/I) data, which has an 85-GHz channel for high spatial resolution (12.5 × 12.5 km 2 ), and was calibrated by comparing with NOAA AVHRR and ADEOS AVNIR visible and near infrared data. The spatial resolution of ice maps derived from this algorithm is 4 times greater per pixel than that of the NASA team algorithm, which uses only low spatial resolution (25 × 25 km 2 ) channels, 19, 22 and 37-GHz. Furthermore the false sea ice signals shown around the coast and marginal ice zone are decreased for all seasons by using this algorithm. This algorithm also attempts to classify sea ice types into fast ice, first-year ice, young ice and new ice by using the difference between the dielectric properties of 85-GHz and 37-GHz channels on different sea ice types with the thickness.