New Routine for Calculating the non-LTE CO2 15 &#956;m Cooling of Mesosphere and Lower themosphere in GCMs
Authors: Kutepov Alexander , Feofilov Artem 
Published: March 2024

The 15 &#956;m CO2 radiative cooling h has significant impact on the energy budget of mesosphere and lower thermosphere (MLT). &#160;Exact calculations of h are critically important for adequate modeling the pressure and temperature distributions in MLT by General Circulation Models (GCMs). Large errors of current routines calculating h significantly influence pressure and temperature distributions in MLT obtained by GCMs. In this study we analyze the errors of the most widely used parameterization of h by Fomichev et al, (1998) and show, that very large errors this parameterization has for temperature profiles disturbed by waves (up to 25 K/Day at mesopause region) are caused by a very approximate solution of the non-local thermodynamic equilibrium (non-LTE) problem. These errors may not be removed in the framework of the parameterization approach, as the revised version of the Fomichev-98 algorithm presented by Lopez-Puertas et al, (2023), shows (see Kutepov, 2023).Instead of developing a new parameterization we present (Kutepov and Feofilov, 2023) for the first time the routine for exact calculating the non-LTE h of MLT in GCMs. The routine is an optimized version of the ALI-ARMS (for Accelerated Lambda Iterations for Atmospheric Radiation and Molecular spectra) non-LTE research code (Feofilov and Kutepov, 2012). It delivers h for day and night conditions with an error (for the current CO2 density) not exceeding 1 K/Day even for strong temperature disturbances. The routine uses the ALI and the Opacity Distribution Function (ODF) techniques adopted from the modeling of stellar atmospheres, and is about 1000 faster than the standard matrix/line-by-line non-LTE solution algorithms. It has an interface for feed-backs from the model, is ready for implementation, may use any quenching rate coefficient of the CO2 (&#957;2 )+O(3P) reaction, handles large variations of O(3P), and allows the user to vary the number of vibrational levels and bands to find a balance between the calculation speed and accuracy. The routine can handle the broad variation of CO2 both below and above the current volume mixing ratio, up to 4000 ppmv. This allows using this routine for modeling the Earth&#8217;s ancient atmospheres and the climate changes caused by increasing CO2. The routine may be downloaded from https://doi.org/10.5281/zenodo.8005028.ReferenceL&#243;pez-Puertas, M., at al. An improved and extended parameterization of the CO2 15 &#956;m cooling in the middle/upper atmosphere,https://doi.org/10.5194/egusphere-2023-2424. Preprint. Discussion started: 6 November 2023, 2023.Feofilov, A. G. and Kutepov, A. A. Infrared Radiation in the Mesosphere and Lower Thermosphere: Energetic Effects and Remote Sensing, Surveys in Geophysics, 33, 1231&#8211;1280, https://doi.org/10.1007/s10712-012-9204-0, 2012.Fomichev, V. I., et al. Matrix parameterization of the 15 &#181;m CO2 band cooling in the middle and upper atmosphere for variable CO2 concentration, Journal of Geophysical Research: Atmospheres, 103, 11 505&#8211;11 528, 475 https://doi.org/10.1029/98jd00799, 1998.Kutepov, A. A, and Feofilov A. G. New Routine NLTE15&#956;mCool-E v1.0 for Calculating thenon-LTE CO2 15 &#956;m Cooling in GCMs of Earth&#8217;s atmosphere, Geophysical Model Development (discussion), https://doi.org/10.5194/gmd-2023-115, 2023.Kutepov, A. A., 'Comment on &#8220;An improved and extended parameterization &#8230; by Lopez-Puertas et al, 2023, https://egusphere.copernicus.org/preprints/2023/egusphere-2023-2424/egusphere-2023-2424-CC1-supplement.pdf, 2023.