On retrieving Rossby waves in the middle atmosphere from measurements of thermal outgoing radiation

The first step is made in elaborating special methods to retrieve the planetary-scale waves for the stratosphere and mesosphere from measurements of thermal outgoing radiation. The method is adapted for the nadir sounding of Rossby normal modes of the Lamb wave type in the 15 μm CO 2 band. The main formulae are presented in a dimensionless form. The proposed method consists of EOF filtering to extract a wave-induced signal and of Hermite polynomial expansions to describe the vertical structure of the wave. The accuracy of the retrievals is estimated; it is dependent on the duration of the record as well as on the number of channels. The method is able to provide a higher accuracy than currently available methods.