Taming the Waves: Using Observations to Tune Gravity Wave Parameterisations in the GEM-Mars GCM

Gravity waves play an important role in the dynamical forcing of the Martian climate. If the horizontal resolution of a Global Climate Model (GCM) is larger than the scale of these waves, their impact should be parameterised to simulate their effects on the mean flow. Typically, the parameterisations derive from Earth models and are not well constrained.

The GEM-Mars GCM (Neary and Daerden, 2018; Daerden et al., 2023) has two schemes: one to simulate the impact of gravity waves from orographic sources such as mountains and topography (McFarlane, 1987), and one for non-orographic sources such as convective forcing and baroclinic waves (Hines, 1997a; 1997b; 2004; Charron et al., 2002). Both schemes calculate a deceleration of the grid-scale winds, often termed “gravity wave drag”. This can have an indirect effect on temperature and on the distribution of trace gases.

The schemes include some “tuning” parameters that can be adjusted to modify when and where this drag occurs. For example, in the non-orographic scheme, the level at which waves are expected to be launched and the lower bound vertical wavenumber, which limits the maximum vertical wavelength of the spectrum allowed, can be adjusted.

Using estimates of wave activity derived from perturbations in observed temperature profiles from the ExoMars Trace Gas Orbiter and MAVEN (Neary et al. submitted), we will explore how these tuning parameters affect the resulting gravity wave drag climatology in GEM-Mars. By comparing model output with observational constraints across latitude, season, and local time, we aim to identify parameter settings that better reproduce the observed distribution and intensity of wave activity. This approach will help assess how well the current parameterisations capture the Martian atmosphere and where further refinement is needed.

References:

Charron, M. et al., 2002. Intercomparison of gravity wave parameterizations: Hines Doppler-spread and Warner and McIntyre ultra-simple schemes. Journal of the Meteorological Society of Japan 80, 335–345.

Daerden, F. et al., 2023. Heterogeneous Processes in the Atmosphere of Mars and Impact on H2O2 and O3 Abundances. Journal of Geophysical Research: Planets 128, e2023JE008014. https://doi.org/10.1029/2023JE008014

Hines, C., 1997a. Doppler-spread parameterization of gravity-wave momentum deposition in the middle atmosphere: Part 1 Basic Formulation. Journal of Atmospheric and Solar-Terrestrial Physics 59.

Hines, C.O., 1997b. Doppler-spread parameterization of gravity-wave momentum deposition in the middle atmosphere. Part 2: Broad and quasi monochromatic spectra, and implementation. Journal of Atmospheric and Solar-Terrestrial Physics 59, 387–400.

Hines, C.O., 2004. The Doppler spread theory and parameterization revisited. Journal of Atmospheric and Solar-Terrestrial Physics 66, 949–956. https://doi.org/10.1016/j.jastp.2004.02.005

McFarlane, N.A., 1987. The effect of orographically excited gravity wave drag on the general circulation of the lower stratosphere and troposphere. Journal of the Atmospheric Sciences 44, 1775–1800.

Neary, L., Daerden, F., 2018. The GEM-Mars general circulation model for Mars: Description and evaluation. Icarus 300, 458–476. https://doi.org/10.1016/j.icarus.2017.09.028

Neary, L., et al., 2026. A multi-mission climatology of gravity waves in the Martian mesosphere and thermosphere. Submitted to Space Science Reviews.