Analysis and characterization of the retrieval algorithm for measuring tropospheric co using the mopitt instrument

We have developed a retrieval algorithm for deriving the tropospheric CO profile and column amount from the radiances measured by the Measurements of Pollution In The Troposphere (MOPITT) instrument. The main components of the algorithm are a fast radiative transfer model, based on the GENLN2 line-by-line model, and a maximum likelihood inversion method. The retrieval a priori information is derived from the results of several aircraft in situ measurements and a three-dimensional chemical transport model. This paper discusses the CO retrieval algorithm with an emphasis on the analysis and characterization of the algorithm. Forward model and retrieval sensitivities, along with the a priori information used in the retrieval are discussed in terms of their orthogonal components. Examples of ensemble retrieval experiments are also included.