Thermal Tides on Mars Before and During the 2018 Global Dust Event as Observed by TIRVIM‐ACS Onboard ExoMars Trace Gas Orbiter.
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| Title: | Thermal Tides on Mars Before and During the 2018 Global Dust Event as Observed by TIRVIM‐ACS Onboard ExoMars Trace Gas Orbiter. |
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| Authors: | Guerlet, S.1,2 (AUTHOR) sandrine.guerlet@lmd.jussieu.fr, Fan, S.1 (AUTHOR), Forget, F.1 (AUTHOR), Ignatiev, N.3 (AUTHOR), Millour, E.1 (AUTHOR), Kleinböhl, A.4 (AUTHOR), Shakun, A.3 (AUTHOR), Grigoriev, A.5 (AUTHOR), Trokhimovskiy, A.3 (AUTHOR), Montmessin, F.6 (AUTHOR), Korablev, O.3 (AUTHOR) |
| Source: | Journal of Geophysical Research. Planets. Sep2023, Vol. 128 Issue 9, p1-27. 27p. |
| Subject Terms: | *Climate change models, *Dust, *Dust storms, *Ozone layer, *Trace gases, Martian atmosphere, Mars (Planet), Atmospheric boundary layer, Tropical climate |
| Abstract: | Migrating tides dominate the tropical climate on Mars and are known to reach high amplitudes during global dust events (GDE). In this study, we characterize the amplitude, phase and vertical wavelength of the diurnal and semidiurnal migrating tides in Mars' lower atmosphere (up to 50 km) by exploiting temperature vertical profiles retrieved from TIRVIM, an infrared spectrometer onboard the ExoMars Trace Gas Orbiter covering multiple local times. Observations from the Mars Climate Sounder onboard the Mars Reconnaissance Orbiter are used to complement the local time coverage when needed, and to estimate a seasonal trend to subtract from TIRVIM observations. We focus on two time periods in Martian Year 34, near Ls = 150° and near Ls = 200° (during the 2018 GDE). The characteristics of the migrating tides at Ls = 150° agree very well with tidal theory: a downward propagation, amplitudes of typically 2–5 K, and a larger vertical wavelength for the semidiurnal compared to the diurnal mode. Comparisons with model predictions from the Mars Planetary Climate Model reveal an excellent agreement, except for a slightly different phase of the diurnal tide. During the GDE, the tide pattern changes spectacularly: the diurnal tide amplitude reaches 35 K at 65°S and 17 K at 50°N, being vertically trapped up to 10 Pa. The semidiurnal tide is maximum near 20–30°S with an amplitude of 8–12 K. The phase of this mode is tilted with latitude, which was not the case before the storm. This indicates a significant contribution of the asymmetric Hough modes due to hemispheric asymmetry in the dust distribution. Plain Language Summary: Important temperature variations are observed in the Martian atmosphere at diurnal scale. Part of these variations are due to a phenomenon called migrating thermal tides, which take the form of global oscillations with periods that are diurnal, or fractions of a day (half a day period = semidiurnal, a third of a day = terdiurnal, etc). Using satellite observations sampling different local times on Mars, we separated these different components and derived their amplitude and phase (the local time at which these oscillations peak) in particular during the global dust event that occurred in 2018. During this major storm, diurnal temperature variations reached 65 K at high southern latitudes near 25 km altitude between the late morning (minimum of temperature) and late evening (maximum of temperature). We also report on the characteristics of the semidiurnal tide and even the terdiurnal tide, which have been less studied during dust storms. The phase of the semidiurnal tide is not the same at all latitudes, which we interpret as a consequence of the asymmetric dust distribution (more dust in the southern hemisphere). Our results agree with predictions from a Global Climate Model, although some small disagreements are found, calling for future improvements in the model. Key Points: The characteristics of the migrating tides derived from TIRVIM at Ls = 150° agree with tidal theory and model predictionsDuring the 2018 global dust event (GDE), the diurnal tide reached an amplitude of 35 K at 65°S and we tentatively detect the terdiurnal tideDuring the 2018 GDE, the semidiurnal tide amplitude reached 10 K at 20°S and exhibited a phase tilt with latitude [ABSTRACT FROM AUTHOR] |
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| Database: | GreenFILE |
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