Gravity Waves in Different Atmospheric Layers During Martian Dust Storms

Gravity waves (GWs) are ubiquitous in the Martian atmosphere and critical for coupling the entire atmospheric system. Recent observations reveal a significant enhancement of thermospheric GW activity in global dust storm conditions, which could increase hydrogen escape. However, the source of these high-altitude GWs and their link to the lower atmosphere are still unknown. We investigate detailed GW distributions and evolutions in three altitude ranges covering the lower, middle, and middle-to-upper transition layers (Lp, Mp, and Hp) of the Martian atmosphere based on multiyear observations from Mars Climate Sounder. The nighttime Mp-layer GWs in the northern tropical region increase significantly after the peak time of regional dust storms, with potential energy 4 times larger than before or at other latitudes. These GWs correlate well with a zonally distributed detached dust layer during storm time, both of which may be generated by a tropical jet system. The upper atmospheric GWs observed during global dust storms are mainly excited in the Hp-layer (similar to 50-70 km) above the main dust layer, except for Mars year 28 global dust storm, when the polar jet in the Mp-layer (similar to 30-50 km) at high northern latitudes may be a major excitation source.