CO2(ν2)-O quenching rate coefficient derived from coincidental SABER/TIMED and Fort Collins lidar observations of the mesosphere and lower thermosphere
Other literature type
Feofilov, A. G.
Kutepov, A. A.
Smith, A. K.
Pesnell, W. D.
Goldberg, R. A.
Among the processes governing the energy balance in the mesosphere and lower
thermosphere (MLT), the quenching of CO<sub>2</sub>(ν<sub>2</sub>) vibrational
levels by collisions with O atoms plays an important role. However, there is
a factor of 3–4 discrepancy between the laboratory measurements of the
CO<sub>2</sub>-O quenching rate coefficient, <i>k</i><sub>VT</sub>, and its value estimated
from the atmospheric observations. In this study, we retrieve <i>k</i><sub>VT</sub> in
the altitude region 85–105 km from the coincident SABER/TIMED and Fort
Collins sodium lidar observations by minimizing the difference between
measured and simulated broadband limb 15 μm radiation. The averaged
<i>k</i><sub>VT</sub> value obtained in this work is 6.5 ± 1.5 × 10<sup>−12</sup> cm<sup>3</sup> s<sup>−1</sup>
that is close to other estimates of this
coefficient from the atmospheric observations. However, the retrieved
<i>k</i><sub>VT</sub> also shows altitude dependence and varies from
5.5 ± 1.1 × 10<sup>−12</sup> cm<sup>3</sup> s<sup>−1</sup> at 90 km to
7.9 ± 1.2 × 10<sup>−12</sup> cm<sup>3</sup> s<sup>−1</sup> at 105 km. Obtained results
demonstrate the deficiency in current non-LTE modeling of the atmospheric 15
μm radiation, based on the application of the CO<sub>2</sub>-O quenching and
excitation rates, which are linked by the detailed balance relation. We
discuss the possible model improvements, among them accounting for the
interaction of the "non-thermal" oxygen atoms with CO<sub>2</sub> molecules.