A new routine for calculating 15um CO2 cooling in the mesosphere and lower thermosphere

We present a new routine for calculating the non-LTE 15 µm CO2 cooling of mesosphere and lower thermosphere in General Circulation Models. It solves the optimized model of the non-LTE in CO2 for daytime and night-time conditions with an error of cooling/heating not exceeding 1 K/Day even for strong temperature disturbances. The routine uses the Accelerated Lambda Iteration and Opacity Distribution Function techniques for the exact solution of the non-LTE problem and is about 1000 faster than the standard matrix/line-by-line solution. It has an interface for feed-backs from the model and is ready for implementation. It may use any quenching rate coefficient of the CO2(ν2)+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 suggested routine can handle the broad variation of CO2 both below and above the current density, up to 4000 ppmv. This allows using this routine for modeling the Earth’s ancient atmospheres and the climate changes caused by increasing CO2.This software accompanies the following publication: "The non-LTE CO2 15 µm Cooling of Mesosphere and Lower Thermosphere: New Routine for Application in General Circulation Models", submitted to Geoscientific Model Development journal by A.Kutepov and A.Feofilov in 2023. The present version of the code can be tested, but it is not supposed to be used operationally until the article passes the review procedure