Carbon dioxide retrievals from NOMAD‐SO on ESA’s ExoMars Trace Gas Orbiter and temperature profiles retrievals with the hydrostatic equilibrium equation: 2. Temperature variabilities in the mesosphere at Mars terminator.

Trompet, L.; Vandaele, A.C.; Thomas, I.; Aoki, S.; Daerden, F.; Erwin, J.; Flimon, Z.; Mahieux, A.; Neary, L.; Robert, S.; Villanueva, G.; Liuzzi, G.; Valverde, Lopez; Brines, A.; Bellucci, G.; Lopez‐Moreno, J. J. and Patel, M. R. (2023). Carbon dioxide retrievals from NOMAD‐SO on ESA’s ExoMars Trace Gas Orbiter and temperature profiles retrievals with the hydrostatic equilibrium equation: 2. Temperature variabilities in the mesosphere at Mars terminator. Journal of Geophysical Research: Planets, 128(3), article no. e2022JE007279.

DOI: https://doi.org/10.1029/2022je007279

Abstract

The Solar Occultation (SO) channel of the Nadir and Occultation for Mars Discovery (NOMAD) instrument scans the Martian atmosphere since 21 April 2018. In this work, we present a subset of the NOMAD SO data measured at the mesosphere. We focused on a spectral range that started to be recorded in Martian year (MY) 35. A total of 968 vertical profiles of carbon dioxide density and temperature covering MY 35 and the beginning of MY 36 were investigated until 135° of solar longitude. We compared 47 profiles with co-located profiles of the Mars Climate Sounder onboard the Mars Reconnaissance Orbiter. Most profiles show a good agreement as SO temperatures are only 1.8 K higher, but some biases lead to an average absolute difference of 7.4°K. The SO data set is also compared with simulations from the Global Environmental Multiscale-Mars general circulation model. Both data sets are in good agreement except for the presence of a cold layer in the winter hemisphere and a warm layer at dawn in the Northern hemisphere for solar longitudes between 240° and 360°. Five profiles contain temperatures lower than the limit for CO₂ condensation. Strong warm layers were found in 13.5% of the profiles. They are present mainly at dawn and in the winter hemisphere, while the Northern dusks appear featureless. The data set mainly covers high latitudes around 60° and we derived some non-migrating tides. In the Southern winter hemisphere, we derived apparent zonal wavenumber-1 (WN-1) and WN-3 tidal components with a maximum amplitude of 10% and 5% at 63 km, respectively.

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