Author: Affiliation: Until recently, a lot of microwave observations were rejected over...

22. The assimilation of microwave observations from AMSU-A and
AMSU-B over sea ice
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.