Use of cloudy radiances for NWP and retrieval of cloud parameters from IASI over Antarctica
Fourrié, Nadia ; Guidard, Vincent ; Rabier, Florence ; Perttula, Tuuli ; Lavanant, Lydie ; Pangaud, Thomas
Advanced infrared sounders, such as the Atmospheric InfraRed Sounder (AIRS) and the Infrared Atmospheric Sounding Interferometer (IASI) on board the first operational European polar-orbiting satellite Metop measure radiation in many thousands of channels. They provide atmospheric temperature and composition information at a much higher vertical resolution and accuracy that could be achieved with the previous generation of satellite instruments such as the High resolution Infrared Radiation Sounder. Nevertheless, the main obstacle to use observation from advanced sounders is the presence of cloud, which can severely limit the information from infrared sounders. In this context, McNally (2002) previously investigated the occurrence of clouds in the sensitive areas with cloud fields from the European Centre for Medium-range Weather Forecasts model. Fourrié and Rabier (2004) also studied the presence of clouds with the AVHRR (Advanced Very High Resolution Radiometer) imager in sensitive areas during FASTEX (Joly et al, 1997). Both studies showed that there was a high correlation between the meteorologically sensitive areas and the cloud cover. Several Numerical Weather Prediction (NWP) centres have thus worked on the assimilation of cloudy radiances since a few years. In this paper we present the approach used for advanced sounders for the assimilation of cloudy radiances at Météo-France and a short study of the retrieval of clouds over Antarctica in the frame of the Concordiasi campaign. The next section presents the retrieval of the cloud parameters in the French global model ARPEGE. The description of the assimilation of AIRS and IASI cloudy radiances is done in section 3. The next section is about the Concordiasi experiment and the study of cloud retrieval over Antarctica. Finally, results are summarized and conclusions are given.
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