Sea ice extent from satellite microwave sensors

provide a convenient way to monitor the vast expanses of sea ice in the Polar Regions and this is done primarily using microwave techniques, which contrary to optical instruments, can operate at night and in all-weather conditions. The determination of sea ice extents from satellite platforms can be exploited as a marker for climate change, a navigation tool and a reference for coupled ocean-ice-atmosphere models. Sea ice detection is routinely performed by two families of microwave instruments: radiometers, which observe the natural emission from the surface in the range of microwave frequencies, and scatterometers, which observe the energy reflected from a transmitted pulse. Earlier work has shown reasonable agreement between scatterometer and radiometer sea ice extents, albeit with systematic discrepancies characterized by defective scatterometer extents during the sea ice growth season1) and deficient radiometer extents during the summer melt2). In this highlight, we revisit the determination of sea ice extents using satellite microwave sensors, propose an improved approach to sea ice detection for the SeaWinds scatterometer based on a Bayesian methodology, and compare its performance against other existing active and passive microwave algorithms throughout a full annual freeze/melt cycle. The improved Bayesian algorithm has been developed for inclusion in the EUMETSAT-KNMI SeaWinds Data Processor and is currently undergoing pre-opera-tional testing.