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
eddy diffusion coefficient
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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.
CitationYoshida, N.; Nakagawa, H.; Aoki, S.; Erwin, J.; Vandaele, A.C.; Daerden, F.; Thomas, I.; Trompet, L.; Koyama, S.; Terada, N.; Neary, L.; Murata, I.; Villanueva, G.; Liuzzi, G.; Lopez-Valverde, M.A.; Brines, A.; Modak, A.; Kasaba, Y.; Ristic, B.; Bellucci, G.; López-Moreno, J.J.; Patel, M. (2022). 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. , Geophysical Research Letters, Vol. 49, Issue 10, e2022GL098485, DOI: 10.1029/2022GL098485.