Intense Zonal Wind in the Martian Mesosphere During the 2018 Planet-Encircling Dust Event Observed by Ground-Based Infrared Heterodyne Spectroscopy

We report on the direct measurements of zonal winds around 80 km altitude during the 2018 planet-encircling dust event (PEDE) by infrared (IR) heterodyne spectroscopy. The observed Doppler shifts assume intense retrograde (easterly) winds (208 +/- 17 m s(-1), 159 +/- 20 m s(-1), 211 +/- 20 m s(-1) on June 21, June 27, August 31, 2018, respectively) in the equatorial region during the 2018 PEDE. This is significantly stronger than those during non-storm conditions reported by the previous study (Sonnabend et al., 2012, ). The substantial retrograde wind during the PEDE is qualitatively consistent with the predictions by the Mars general circulation models (MGCMs), however, the observed wind on 31, August, are of a larger magnitude. We evaluated the mechanism of acceleration using the output from a high-resolution MGCM. We find out that the stronger winds are related to strengthening the meridional circulation across the equator and forcing by gravity waves.

Automated summary

Direct measurements of zonal winds around 80 km altitude during the 2018 planet-encircling dust event (PEDE) show significantly stronger retrograde winds in the equatorial region compared to non-storm conditions. The observed wind speeds are qualitatively consistent with Mars general circulation models (MGCMs), but stronger winds on August 31 indicate additional mechanisms at play. Strengthening of the meridional circulation across the equator and forcing by gravity waves contribute to the acceleration of winds during PEDE.