Vladimir P. Ogibalov

The near-infrared (NIR) emission of the Martian atmosphere in the CO2 bands at 4.3, 2.7, 2.0, 1.6, 1.4, 1.3, 1.2, and 1.05 µm and in the CO bands at 4.7, 2.3, 1.6, and 1.2 µm is mainly generated under nonlocal thermodynamic equilibrium (NLTE) conditions for vibrational states, the transitions from which form the specified bands. The paper presents the results of simulations of the population of these states under NLTE for daytime conditions. In the cold high-latitude troposphere, the NLTE takes place much lower than in the troposphere under typical temperature conditions. If the NIR-radiation reflection from the surface is ignored, the population of high vibrational states substantially decreases, at least, in some layer of the lower atmosphere. However, inelastic collisions of CO₂ and CO molecules with O atoms produce no considerable influence on the values of populations. The population of vibrational states, the transitions from which form NIR bands, is also almost insensitive to possible large values of the quenching-in-collision rate constants of vibrational states higher than CO₂(00⁰1). However, very large errors in the estimates of the population of vibrational states of the CO₂ molecule (rather than the CO molecule!) can be caused by the uncertainty in the values of the rate constant of exchange between CO² molecules by the energy quantum of the asymmetric stretching vibrational mode. For this intermolecular exchange, we recommend a possible way to restrict the vibrational excitation degree of the molecule that is a collision partner and to maintain simultaneously a sufficiently high accuracy in the population estimate.

Advances in attacking the problem of radiative transfer in the near infrared (NIR) bands of CO and CO under nonlocal thermodynamic equilibrium (NLTE) conditions depend on the accuracy of taking into account the radiation processes and inelastic collisions of CO and CO molecules. The focus of the paper is to substantially improve the physical model of the problem and update the calculation method. It is the first time the surface albedo is introduced into the problem of the molecular emission under NLTE conditions. The values of the rate constants for inelastic molecular collisions and their temperature dependences have been radically updated. In some cases, since laboratory measurements of these constants are lacking, different versions are provided for them. The relative abundance of CO and CO isotopologues is based on the ratios of isotope abundances for the elements C and O obtained from the measurements in the atmosphere of Mars. The intensity of extraterrestrial solar NIR radiation is specified on the base of the high-accuracy ground-based measurements. In the method for calculating the populations of vibrational states, we pioneer in completely taking into account the overlapping of spectral lines in the NIR bands of CO and CO.

Increase in the nighttime high-latitude nonthermal emissions in the mesosphere and lower thermosphere in the 4.3 and 15 µm CO2bands during solar proton events has been estimated for the first time....

The effect of tidal perturbations in temperature on the rate of cooling the upper mesosphere and lower thermosphere in the CO215-µm band is revised. It is shown that the effect of solar semidiurnal...

Absorption of solar energy by the near‐infrared (NIR) CO₂ bands provides an important source of heating in the mesosphere. At 60–85 km, this source exceeds 1 K day⁻¹ and contributes up to 30% of the total solar heating. Calculation of the solar heating in the NIR CO₂ bands requires consideration of complex non‐local thermodynamic equilibrium (non‐LTE) processes. The small energy effect, narrow region of importance, and the necessity to consider non‐LTE effects, have accounted for the absence of an adequate parameterization for the NIR CO₂ bands. Recently a parameterization has been developed and implemented into the Canadian Middle Atmosphere Model. Numerical experiments with this model have shown that inclusion of the NIR CO₂ heating results in a significant warming of up to 8 K in the mesosphere for the current CO₂ amount but does not significantly change the model thermal response induced by the doubling of CO₂.

This paper presents the thermal response of the Canadian middle atmosphere model (CMAM) to minor radiative energy sources and sinks. These include chemical heating, infrared (IR) H₂O cooling, sphericity effect in solar heating, and solar heating in the near‐IR CO₂ bands. All of these energy sources/sinks can be considered as minor ones either in terms of their magnitude or in terms of the limited height region where they are of importance or both. To examine the thermal response of the middle atmosphere, a version of the CMAM with an interactive gas phase chemistry scheme has been used in a series of multiyear experiments for conditions of perpetual July. Each of the analyzed mechanisms may provide a noticeable contribution into the model energy balance that results in a statistically significant model response. Various forcing terms due to minor energy sources/sinks have different spatial and temporal distributions. Their magnitudes vary from tenths K d⁻¹ for the sphericity effect up to ∼10 K d⁻¹ for chemical heating that provides corresponding thermal responses of a few to about 20 K in the middle atmosphere. The model thermal response depends on the magnitude of the applied forcing but is not always local and can be spread beyond the regions where the forcing terms are initially applied. On a globally averaged basis the local strength of the model response is nearly proportional to the magnitude of the small forcing terms but shows nonlinearity when forcing due to chemical heating exceeds ∼1 K d⁻¹ in the mesosphere. Accounting for the combined effects of the minor energy sources and sinks leads to a better agreement between the model temperature field and observations.

The paper presents the first laboratory measurement of the rate constant for quenching the CO₂(01¹0) state during collisions of CO₂ molecules with O atoms at temperatures realized near the Earth's mesopause. The measurement was carried out with a hollow-cathode glow discharge in the temperature range 206-358 K. The measured values are significantly smaller than those commonly used in solving the non-LTE CO₂ problem for the vibrational states of the mode ν₂ in the atmospheres of the Earth, Venus, and Mars. The measured temperature dependence of the rate constant is approximated by a simple relation, which is recommended for solving the above problem. The value of this rate constant is absolutely critical to remotely sense temperature, and hence also constituent densities, in the upper mesosphere and lower thermosphere of the Earth. The use of the new values of the rate constant significantly decreased the rate of cooling by the CO₂ 15-μm emission in the terrestrial lower thermosphere as compared to the previous estimates obtained for this rate. Over the most area of the Earth's surface, the maximum cooling rate occurs at an altitude of about 110 km and amounts to about 20 K/day.