We report the gravity wave (GW) statistics accumulated over two Martian years from the second half of Martian Year 34 (MY34) to the middle of MY36 (May 2018 - February 2022). The observations were performed by the middle- and near-infrared (MIR and NIR, respectively) spectrometers of Atmospheric Chemistry Suite (ACS) on board ExoMars Trace Gas Orbiter (TGO). Temperature profiles obtained independently of both channels during simultaneous measurements show a good agreement, thus providing verification and additional confidence in the data. GW parameters such as temperature fluctuations, potential energy per unit mass, and wave drag are retrieved at altitudes up to 160 km from the MIR channel and up to 100 km from the NIR channel. We present seasonal, intraday and latitude distributions of the wave potential energy and drag, serving to represent the wave activity and impact on the dynamics. A comparison of data obtained during the global dust storm (GDS) of MY34 with the corresponding period of MY35 without a storm reveals a reduction of GW activity in mid-latitudes in agreement with previous observations, and enhancement in the polar regions of both hemispheres, which was predicted by theoretical studies using simulations with a high-resolution circulation model. Seasonal variations of the derived GW activity can be linked to changes in the solar tide.

The paper presents observations of gravity wave-induced temperature disturbances in the Martian atmosphere obtained with the mid-infrared (MIR) spectrometer, a channel of the Atmospheric Chemistry Suite instrument on board the Trace Gas Orbiter (ACS/TGO). Solar occultation measurements of a CO2 absorption band at 2.7 μm were used for retrieving density and temperature profiles between heights of 20 and 160 km with vertical resolution sufficient for deriving small-scale structures associated with gravity waves. Several techniques for distinguishing disturbances from the background temperature have been explored and compared. Instantaneous temperature profiles, amplitudes of wave packets and potential energy have been determined. Horizontal momentum fluxes and associated wave drag have been estimated. The analyzed data set of 144 profiles encompasses the measurements made over the second half of Martian Year 34, from the Solar longitude 165◦ through 355◦. We observe enhanced gravity wave dissipation/breaking in the mesopause region of 100-130 km. Our analysis shows no direct correlation between the wave amplitude and Brunt-Vaisala frequency. It may indicate that convective instability may not be the main mechanism limiting gravity wave growth in the middle atmosphere of Mars.