JGR (2023) https://doi.org/10.1029/2022JE007277
L. Trompet, A.C. Vandaele, I. Thomas, S. Aoki, F. Daerden, J. Erwin, Z. Flimon, A. Mahieux, L. Neary, S. Robert, G. Villanueva, G. Liuzzi, Lopez-Valverde, A. Brines, G. Bellucci, J. J. Lopez-Moreno, M. R. Patel
The SO (Solar Occultation) channel of the Nadir and Occultation for Mars Discovery (NOMAD) instrument has been scanning the Martian atmosphere for almost two Martian years. In this work, we present a subset of the NOMAD SO data measured at the mesosphere at the terminator. From the dataset, we investigated 968 vertical profiles of carbon dioxide density and temperature covering Martian Year (MY) 35 as well as MY 36 up to a solar longitude (Ls) of 135° and altitudes around 60 km to 100 km. While carbon dioxide density profiles are directly retrieved from the spectral signature in the spectra, temperature profiles are more challenging to retrieve as unlike density profiles, temperature profiles can present some spurious features if the regularization is not correctly managed. Comparing seven regularization methods, we found that the expected error estimation method provides the best regularization parameters. The vertical resolution of the profiles is on average 1.6 km. Numerous warm layers and cold pockets appear in this dataset. The warm layers are found in the Northern hemisphere at dawn and dusk as well as in the Southern hemisphere at dawn. Strong warm layers are present in more than 13.5% of the profiles. The Southern hemisphere at dusk does not present any warm layer between Ls 50° and 150°. The height and latitudinal distribution of those warm layers are similar in MY 35 and MY 36 during the first half of the year (Ls=0 - 135°).
Retrieved temperature for a pressure of 0.1 Pa over MY 35 and MY 36 until Ls 135° as a function of solar longitude (panels a and b), as a function of local solar time (panel c), and as a function of latitude (panel d). In Panel a, the color code corresponds to the solar local time, and in panel b to the latitude. Local solar time and latitudinal trends are present in panels a and b.
