CO<sub>2</sub>(ν<sub>2</sub>)-O quenching rate coefficient derived from coincidental SABER/TIMED and Fort Collins lidar observations of the mesosphere and lower thermosphere
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...
| Main Authors: | , , , , , |
|---|---|
| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2012-10-01
|
| Series: | Atmospheric Chemistry and Physics |
| Online Access: | http://www.atmos-chem-phys.net/12/9013/2012/acp-12-9013-2012.pdf |
| Summary: | 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. |
|---|---|
| ISSN: | 1680-7316 1680-7324 |