Channel selection methods for Infrared Atmospheric Sounding Interferometer radiances

Advanced infrared sounders, will provide thousands of radiance data at every observation location. The number of individual pieces of information is not usable in an operational numerical weather-predict ion context. and we have investigated the possibilities of choosing an 'optimal' subset of data, These issues have been addressed in the context of optimal linear estimation theory. using simulated Infrared Atmospheric Sounding Interferometer data, Several methods hake been tried to select a set of the most useful channels for each individual atmospheric profile. These are two methods based on the data resolution matrix, one method based or) the Jacobian matrix. and one iterative method selecting sequentially the channels with largest information content. The Jacobian method and the iterative method ere found to be the most suitable for the problem, The iterative method as demonstrated to always produce the best results, but at a larger cost than the Jacobian method. To test the robustness of the iterative method, a variant has been tried. It consists in building a mean channel selection aimed at optimizing the results over the whole database, and then applying to each profile this 'Constant' selection, Results show that this 'constant' iterative method is very promising. with results of intermediate quality between the ones obtained for the optimal iterative method and the Jacobian method. The practical advantage of this method for operational purpose is that the same set of channels can be used for various atmospheric profiles.