Variations in Vertical CO/CO2 Profiles in the Martian Mesosphere and Lower Thermosphere Measured by the ExoMars TGO/NOMAD: Implications of Variations in Eddy Diffusion Coefficient
Abstract
Using the Nadir and Occultation for MArs Discovery instrument aboard Trace Gas Orbiter, we derived the CO/CO2 profiles between 75 and 105 km altitude with the equivalent width technique. The derived CO/CO2 profiles showed significant seasonal variations in the southern hemisphere with decreases near perihelion and increases near aphelion. The estimation of the CO/CO2 profiles with a one-dimensional photochemical model shows that an altitude-dependent eddy diffusion coefficient better reproduces the observed profiles than a vertically uniform one. Our estimation suggests that the eddy diffusion coefficient in Ls = 240-270 is uniformly larger by a factor of ∼2 than that in Ls = 90-120 in the southern hemisphere, while they are comparable in the northern hemisphere. This fact demonstrates that the eddy diffusion coefficient is variable with season and latitude.
- Publication:
-
Geophysical Research Letters
- Pub Date:
- May 2022
- DOI:
- 10.1029/2022GL098485
- Bibcode:
- 2022GeoRL..4998485Y
- Keywords:
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- Mars;
- eddy diffusion coefficient;
- atmospheric composition;
- mesosphere;
- spectroscopy;
- retrieval