The application of AIRS radiances in numerical weather prediction

(Aumann et al. 2003) was launched on AQUA the second of the EOS polar-orbiting satellites. The AIRS was the first of a new generation of meteorological advanced sounders able to provide hyper-spectral data for operational and research use. A large investment has been made internationally to upgrade the meteorological satellite systems to carry these advanced instruments. The US Cross-track Infrared Sounder (CrIS) and Geosynchronous Imaging Fourier Transform Spectrometer (GIFTS), as well as the European Infrared Atmospheric Sounding Interferometer (IASI) represent significant investment in these systems. As a result, demonstration of the benefit of hyperspectral data on numerical weather prediction (NWP) has been a high priority. Observing system experiments designed to examine effective methods to use AIRS hyperspectral radi-ances are summarised here. The first experiments to use full spatial resolution hyperspectral radiance data, available in real time from the AIRS instrument are reviewed. The result of these assimilation trials was significant improvements in forecast skill, compared to the global system without AIRS data over both the northern and southern hemispheres. In addition , an experiment is described which showed the advantage of using all AIRS fields of view in analysis as opposed to the use of sampled fields of view (typically one-in-eighteen) often used for NWP. Experiments showing the impact of using hyperspec-tral data of different spectral coverage are also described, and show the importance of careful selection of instrument channels for assimilation. Overall, the results indicate the significant benefits to be derived from AIRS data assimilation and the benefits to be gained from an enhanced use of the information content contained in the AIRS radiance observations.