The MT_CKD continuum model includes continuum absorption due to water vapor, nitrogen, oxygen, carbon dioxide, and ozone.  Also, optical depths associated with Rayleigh scatterring may be computed.  The water vapor continuum represents the  first recomputation of the entire self and foreign broadened continuum since the original model was developed in the  1980s.  This version of the continuum is implemented in the line-by-line model LBLRTM v7.0 and will be utilized in all related AER Radiative  Transfer models.

The MT_CKD continuum is based on a new formulation: The self and foreign continuum models are each based on the contributions from two components: a collision induced component and a line shape component.  This change in perspective has resulted from the difficulty in developing a line shape model based on sound physics that explains the magnitude of the increased absorption in the intermediate wing over that provided by the impact  approximation.

These two components are applied consistently to all water vapor lines  from the microwave to the visible, and the results summed to obtain self  and foreign continuum coefficients from 0-20,000 cm-1.  Eight and seven  parameters are needed to specify the two components for the self and  foreign continua, respectively, which are sufficient to generate the  entire continuum spectrum over this spectral domain.  The ratio of the  self continuum at 296 K to that at 260 K has been kept the same as in the  CKD model.  The only temperature dependence for the foreign continuum  arises from the radiation term as with CKD.  The MT_CKD model as with CKD,  should be regarded as a semi empirical model with strong constraints  provided by the known physics.

The data that have been used to develop the new continuum model has come  predominantly from spectral atmospheric measurements.  Only cases for which  the characterization of the atmospheric state has been highly scrutinized  have been used.  This new model has been developed by E.J. Mlawer,  D.C. Tobin and S.A. Clough building on the original CKD formulation; hence  the name MT_CKD.