22. The assimilation of microwave observations from AMSU-A and AMSU-B over sea ice Author： Fatima Karbou, Florence Rabier Affiliation： Meteo-France, CNRM-GAME/CEN Until recently, a lot of microwave observations were rejected over sea ice during the assimilation process. Inappropriate description of sea ice in the model (constant value of 0.99) is one of the reasons for such a limited use of observations. Following the work on the land surface emissivity undertaken at Meteo-France (Karbou et al. 2010ab), a new sea ice emissivity model has been developed covering the frequency range of 23 to 150 GHz. This model was built by studying the spatial and temporal variability of the emissivity of sea ice directly inferred from satellite observations. The model was evaluated in the context of global assimilation experiments by assimilating, for the first time, observations sensitive to the surface from AMSU-A and AMSU-B. It has been shown that the use of this model allows the assimilation of the surface sensitive channels over polar regions and at the same time improves the quality of analyses/forecasts of the global model ARPEGE. In this presentation, the sea-ice emissivity model will be presented and its impact within the radiative transfer model RTTOV quantified. We will then give elements on the data impact studies carried out during the winter of 2009/2010.