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.

Automated summary

Gravity waves are widely present in the Martian atmosphere and play a critical role in the coupling of the entire atmospheric system. Recent observations show that thermospheric gravity wave activity is significantly enhanced during global dust storms, which could lead to increased hydrogen escape. However, the source of these high-altitude gravity waves and their connection to the lower atmosphere remains unknown.