Variations in Vertical CO/CO<SUB>2</SUB> Profiles in the Martian Mesosphere and Lower Thermosphere Measured by the ExoMars TGO/NOMAD: Implications of Variations in Eddy Diffusion Coefficient

DOI: 
10.1029/2022GL098485
Publication date: 
08/05/2022
Main author: 
Yoshida, Nao
IAA authors: 
Lopez-Valverde, Miguel Angel;Brines, Adrian;Modak, Ashimananda;López-Moreno, José Juan
Authors: 
Yoshida, Nao;Nakagawa, Hiromu;Aoki, Shohei;Erwin, Justin;Vandaele, Ann Carine;Daerden, Frank;Thomas, Ian;Trompet, Loïc.;Koyama, Shungo;Terada, Naoki;Neary, Lori;Murata, Isao;Villanueva, Geronimo;Liuzzi, Giuliano;Lopez-Valverde, Miguel Angel;Brines, Adrian;Modak, Ashimananda;Kasaba, Yasumasa;Ristic, Bojan;Bellucci, Giancarlo;López-Moreno, José Juan;Patel, Manish
Journal: 
Geophysical Research Letters
Refereed: 
Yes
Publication type: 
Article
Volume: 
49
Pages: 
e98485
Abstract: 
Using the Nadir and Occultation for MArs Discovery instrument aboard Trace Gas Orbiter, we derived the CO/CO<SUB>2</SUB> profiles between 75 and 105 km altitude with the equivalent width technique. The derived CO/CO<SUB>2</SUB> profiles showed significant seasonal variations in the southern hemisphere with decreases near perihelion and increases near aphelion. The estimation of the CO/CO<SUB>2</SUB> 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 L<SUB>s</SUB> = 240-270 is uniformly larger by a factor of ∼2 than that in L<SUB>s</SUB> = 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.
Database: 
ADS
SCOPUS
URL: 
https://ui.adsabs.harvard.edu/#abs/2022GeoRL..4998485Y/abstract
ADS Bibcode: 
2022GeoRL..4998485Y
Keywords: 
Mars;eddy diffusion coefficient;atmospheric composition;mesosphere;spectroscopy;retrieval