Exploring gravity wave activity in the Martian atmosphere using ExoMars TGO/NOMAD observations and modelling

On Mars, gravity-wave induced density and temperature fluctuations have been observed by orbiting platforms (e.g. [1-5]), during aerobraking [6-7] and from the surface [8]. Their effects are also seen in airglow imagery [9].

We present a climatology of gravity wave activity as seen by the ExoMars Trace Gas Orbiter (TGO) Nadir Occultation for MArs Discovery (NOMAD) instrument [10] and explore the seasonality and latitudinal variability of perturbations seen in the upper atmosphere. Using the Solar Occultation (SO) observation mode of NOMAD, we can also examine the differences in activity at sunrise and sunset.  Two different infrared wavelength regions are used to retrieve CO₂ densities in the troposphere (below 50 km) and in the mesosphere (50-100km). From these densities, we can infer temperatures [11, 12], and investigate the perturbations seen in the vertical profiles.

The GEM-Mars Global Circulation Model (GCM) [13, 14] uses two parameterisations for the impacts of orographic [15] and non-orographic gravity waves [16-18], originating from the terrestrial version of the model [19-21]. By comparing temperatures, mapping the perturbations and analysing the derived potential energy and gravity wave drag from the observations, we can then adjust the schemes’ tuning parameters to better match the NOMAD temperatures. For example, in the non-orographic scheme, the lower bound vertical wavenumber, which limits the maximum vertical wavelength of the spectrum allowed, can be adjusted. Various sensitivity studies will be shown.

Acknowledgements

This project acknowledges funding from the Belgian Science Policy Office (BELSPO) (grant B2/223/P1/MOMENTUM). The NOMAD experiment is led by the Royal Belgian Institute for Space Aeronomy (IASB-BIRA) with co-PI teams from Spain (IAA-CSIC), Italy (INAF-IAPS) and the United Kingdom (Open University). This project acknowledges funding by: BELSPO with the financial and contractual coordination by the ESA Prodex Office (PEA 4000103401, 4000121493, 4000140753, 4000140863); by the Spanish Ministry of Science and Innovation (MCIU) and European funds (grants PGC2018-101836-B-I00 and ESP2017-87143-R; MINECO/FEDER), from the Severo Ochoa (CEX2021-001131-S) and from MCIN/AEI/10.13039/501100011033 (grants PID2022-137579NB-I00, RTI2018-100920-J-I00 and PID2022-141216NB-I00); by the UK Space Agency (grants ST/V002295/1, ST/V005332/1, ST/X006549/1, ST/Y000234/1 and ST/R003025/1); and by the Italian Space Agency (grant 2018-2-HH.0).

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