Seasonal variability of CO in the terrestrial mesosphere

We measured the J = 1 → 2 rotational transition of terrestrial mesospheric CO both in emission and in absorption against the moon on January 25–26, 1982. A CO mixing profile was obtained from the high signal‐to‐noise ratio emission spectrum. With the inclusion of these most recent spectra and spectra measured by Kunzi and Carlson (1982) we find further evidence suggesting seasonal variation of mesospheric CO as originally reported by Clancy et al. (1982). This seasonal variation may be the consequence of hemispheric circulation in the upper atmosphere.