Infrared atmospheric sounding interferometer data information content; instrument characterization and the impact of a priori information

The use of linear estimation for the study of the information content of a given satellite radiance data set for temperature and humidity profile retr ievals is first reviewed. A particular formulation of the retrieval approac h is then used to obtain an intrinsic characterisation of the infrared Atmo spheric Sounding Interferometer (IASI) data set, in terms of accuracy versu s vertical resolution of retrieved profiles. The performance of the IASI in strument alone is analysed and compared to that of the currently-used WIRS- TOVS. The problem is then regularization by addition of a priori independen t information to the initial data set. The potential use of IASI data for s ome particular choices of the a priori information associated with practica l problems such as profile inversion or data assimilation for weather forec asting is analysed. The approach is finally used to derive an "empirical" o bjective framework to definite the vertical discretization adapted to these problems.