Improvements to the correlated-k radiative transfer method: Application to satellite infrared sounding

This paper presents a new radiative transfer model based on the correlated-k technique that is particularly suitable for applications associated with broadband infrared satellite remote sounding of the atmosphere. We describe new developments to the approach which improve the accuracy of correlated-k distribution radiative transfer calculations. These include methods to model an instrument response function, spectral line overlap for multiple gases, and the spectral variation of solar and thermal source functions. We also describe an approach to improving vertical spectral correlation along ray paths through a nonhomogeneous atmosphere. For a radiative transfer model to be efficient as the forward model of a retrieval scheme, the calculation of analytical Jacobians is particularly important. This is implemented in the model using a variation on the correlated-k approach. The application of the new model, RADCKD, is demonstrated with example calculations for the EOS Terra satellite Measurements of Pollution in the Troposphere (MOPITT) instrument.