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.
The MT_CKD model is available as a separate module, but is present in the models LBLRTM and MONORTM (subroutine 'contnm.f').