Variations in the Mesospheric OH Vibrational Distributions
Abstract
Intensity-calibrated sky spectra from the Keck II telescope on Mauna Kea, measured throughout the visible and the infrared to 1.09 microns, show that there is substantial variation in the vibrational distribution of OH(v=3-9) during the night. From five nights of observation in March 2000, utilizing low-J lines of the 3-0 and 9-5 bands near 1 micron, the v=3 population typically fell by a factor of 2-4 over a 9-hour period, while the N(v=3)/N(v=9) population ratio simultaneously decreased, by a factor of about two. Although the intensity changed in a different manner during four observing nights in October 2000, two in July 2000, and one in July 2001, the v=3 population and the N(v=3)/N(v=9) ratio still co-vary. The total range of the ratio in our observations is 4-15. The vibrational distribution presented by McDade and Llewellyn [JGR, 92, 7643, 1987], based on various measurements, results in a value of 6.6±0.7 for the ratio. Observations from the infrared SABER instrument on the TIMED satellite in March 2002 indicate that the highest OH intensities are seen at the lowest altitudes, and that the highest [low-v]/[high-v] intensity ratios are associated with the highest OH intensities. The presumption is that decreasing [low-v]/[high-v] ratios are indicative of increasing altitude and decreasing density in the glowing layer. We believe that the N(v=3)/N(v=9) ratio as viewed from the ground defines the emission altitude and/or species density in the OH nightglow region. This study was supported by a grant from the NSF Aeronomy program.
- Publication:
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AGU Spring Meeting Abstracts
- Pub Date:
- May 2004
- Bibcode:
- 2004AGUSMSA13A..05S
- Keywords:
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- 0300 ATMOSPHERIC COMPOSITION AND STRUCTURE;
- 0310 Airglow and aurora;
- 0317 Chemical kinetic and photochemical properties;
- 0340 Middle atmosphere: composition and chemistry;
- 0342 Middle atmosphere: energy deposition