Global Distribution of Gravity Wave Sources and Fields in the Martian Atmosphere during Equinox and Solstice Inferred from a High-Resolution General Circulation Model

Abstract

Abstract Results of simulations with a new high-resolution Martian general circulation model (MGCM) (T106 spectral resolution, or ~67-km horizontal grid size) have been analyzed to reveal global distributions of gravity waves (GWs) during the solstice and equinox periods. They show that shorter-scale harmonics progressively dominate with height, and the body force per unit mass (drag) they impose on the larger-scale flow increases. Mean magnitudes of the drag in the middle atmosphere are tens of meters per second per sol, while instantaneously they can reach thousands of meters per second per sol. Inclusion of small-scale GW harmonics results in an attenuation of the wind jets in the middle atmosphere and in the tendency of their reversal. GW energy in the troposphere due to the shortest-scale harmonics is concentrated in the low latitudes for both seasons and is in a good agreement with observations. The vertical fluxes of wave horizontal momentum are directed mainly against the larger-scale wind. Orographically generated GWs contribute significantly to the total energy of small-scale disturbances and to the drag created by the latter. These waves strongly decay with height, and thus the nonorographic GWs of tropospheric origin dominate near the mesopause. The results of this study can be used to better constrain and validate GW parameterizations in MGCMs.