A Computationally Efficient Retrieval Algorithm for Hyperspectral Sounders Incorporating A Priori Information

In this letter, we describe a novel implementation scheme for the inversion of the radiative-transfer equation as encountered in satellite remote sensing and incorporating a priori information. Unlike traditional maximum a posteriori approaches, the new algorithm does not require the use of a forward-model tangent linear and does not pay a large computational time penalty in the use of numerical derivatives. Using spectral data from the European Organisation for the Exploitation of Meteorological Satellites´ Infrared Atmospheric Sounding Interferometer sensor, we provide a demonstration of the algorithm and comparison to the National Oceanic and Atmospheric Administration´s operationally available product using carbon monoxide as target gas.