Gravity wave activity in the Martian atmosphere at altitudes 20-160 km
from ACS/TGO occultation measurements
Abstract
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.