What is the temperature and carbon dioxide concentration in the mesosphere?

In a recent paper (Tuck et al., 2005) demonstrated that translationally hot oxygen atoms produced subsequent to ozone photolysis in the stratosphere implied the strong likelihood of non-Maxwell-Boltzmann (MB) molecular velocity distributions in the daytime. In other words, the stratospheric temperature is not characterized by a classic MB distribution. This would have implications, for example, for rates of chemical reactions and line shapes of radiatively active molecules, both of which are temperature dependent. In the mesosphere and lower thermosphere, where there is substantially more excess energy from photolysis and from energy released by exothermic chemical reactions, the likelihood of non-MB velocity distributions appears even higher. We review the generation of heat in the mesosphere and the production of hot atoms and molecules, discussing the possible generation of non-MB distributions, and hence the meaning of "temperature" in the mesosphere. We also discuss possible implications for radiative transfer, energy balance, and chemical composition in the mesosphere. In addition, understanding the energy balance in the mesosphere requires knowledge of the carbon dioxide concentration. Current remote measurement techniques face challenges due to the opacity of carbon dioxide in the infrared. Accurate in-situ measurements, coupled with satellite overflights offer high potential for substantial scientific progress in this critical area. We discuss the potential for new suborbital vehicles to make unique contributions to aeronomic science through the measurement of temperature and carbon dioxide in the mesosphere. Tuck, A. F., et al., (2005), Molecular velocity distributions and generalized scale invariance in the turbulent atmosphere, Faraday Discuss., 130, 181-193. DOI: 10.1039/b410551f.