Climatological Gravity Waves in the Middle and Upper Atmosphere of Mars Based on ACS/TGO Observations

Abstract

Gravity waves (GWs) are important for the vertical coupling of the Martian atmosphere. The middle atmosphere is the key region where GWs propagate to the upper thermosphere and generate momentum and energy exchange, but the knowledge of middle-atmosphere GWs is incomplete, due to the lack of observations with the kilometer-scale resolution. We have analyzed the climatology of GW activity in the middle and upper atmosphere of Mars using 20–180 km temperature profiles measured by the Atmospheric Chemistry Suite instrument on board the Trace Gas Orbiter. The results show that the amplitudes of GWs extracted in this study are generally less than 15% and that the centers of the strongest GW activity vary significantly with the seasons. Second, the strongest GW activity in the mesosphere indicates the strong dissipation effects of the mesopause, and the mid-atmospheric GWs show a seasonal pattern that is stronger in the winter hemisphere. During the global dust event of MY34, the enhancement of GWs in the middle atmosphere is most pronounced at low and middle latitudes where the dust storms are active. It is possible that changes in the temperature structure of the middle atmosphere adjust the atmospheric circulation and thus improve the propagation of GWs. Furthermore, GW activity is stronger on the dayside than on the nightside, and there is no significant correlation between amplitudes and background temperature. This suggests a limited role of convective instability in limiting the growth of GWs in the middle atmosphere, with nonlinear damping competing with that of molecular diffusion at different harmonics.

On the Gravity Wave‐Seeded Ionospheric Irregularities in the Martian Ionosphere

“…Ji et al (2022) also suggested an association between N 2 being less than zero and GWB on Mars, so we calculate Brunt-Väisälä frequencies (N) based on neutral atmospheric CO 2 density and take N 2 less than zero as an index of GWB. The calculation methods are used by Manju and Mridula (2020) and Ji et al (2022Ji et al ( , 2023, and the specific procedure is as follows.…”

Climatology of gravity wave activity based on two Martian years from ACS/TGO observations

“…That database covered observations for 1.5 Martian years (MYs), from the middle of MY 34 to the end of MY35. The same volume of the ACS-MIR/TGO data was recently analyzed by Ji et al (2023) applying another algorithm of extracting wave components.…”