The inclusion of the MT_CKD water vapor continuum model in the HITRAN molecular spectroscopic database

Atmospheric radiative transfer calculations require information about the spectral absorption properties of all relevant gases in the atmospheric path. For years, much of the atmospheric community has relied on the HITRAN molecular spectroscopic database for absorption line information and the MT_CKD (Mlawer-Tobin_Clough-Kneizys-Davies) water vapor continuum model to specify water vapor continuum absorption. This paper reports on efforts related to the recent inclusion of the MT_CKD water vapor continuum model as a component of HITRAN. Details are provided about the restructuring of the MT_CKD model to separate its code and data and simplify the code structure. We also describe the reformulation of the temperature dependence of the water vapor self continuum in MT_CKD, motivated both by improvements to the model's accuracy at high temperatures and greater consistency with HITRAN. We also briefly describe other recent updates to the MT_CKD water vapor continuum. Finally, perspective is provided on the need for future water vapor continuum measurements. The code and data for the MT_CKD water vapor continuum are available through the HITRAN website at https://hitran.org/mtckd and at the AER GitHub site at https://github.com/AER-RC/MT_CKD_H2O.