Use of C-Band Scatterometer for Sea Ice Edge Identification

This paper describes use of Advanced Scatterometer (ASCAT) C-band scatterometer data for determination of the sea ice edge. The variation in backscatter with measurement geometry is different for the sea ice surface compared to the open water surface. Utilizing the ASCAT antenna configuration with three different look angles for the same surface spot, a new ASCAT sea ice parameter has been defined. One year of ASCAT measurements has been collocated with background sea ice information to derive probability distributions for the ASCAT sea ice parameter given the known ice condition. The result can be used in an inverse methodology, a Bayesian approach, to calculate the probability of sea ice from the ASCAT measurements. The method has been tested for a full year and validated against high-resolution satellite images and ice charts from an operational Ice Service. It reveals a realistic ice edge result, however, with weather-induced noise problems in terms of false sea ice. For automatic ice edge detection, ancillary information is needed to remove this noise. The paper shows how the method also can be used for ice edge detection with passive microwave data from SSM/I, and how it can be extended to utilize ASCAT together with SSM/I in a multisensor approach.