Gravity Wave Activity in the Atmosphere of Mars During the 2018 Global
Dust Storm: Simulations With a High-Resolution Model
Abstract
Gravity wave activity in the lower and middle atmosphere of Mars during
the global dust storm of 2018 has been studied for the first time using
a high-resolution (gravity wave resolving) general circulation model.
Dust storm simulations were compared with those utilizing the
climatological distribution of dust in the absence of storms. Both
scenarios are based on observations of the dust optical depth by the
Mars Climate Sounder instrument on board the Mars Reconnaissance
Orbiter. The modeling reveals a reduction of the wave activity by a
factor of two or more in the lower atmosphere, which qualitatively
agrees with recent observations. It is associated with a decline of
gravity wave generation due to baroclinic and convective stabilization
of the Martian troposphere induced by the increased amount of airborne
aerosols during the storm. Contrary to the decrease of GW activity in
the lower atmosphere, wave energy and momentum fluxes in the middle
atmosphere increase by approximately the same factor. This enhancement
of gravity wave activity is caused by the changes in the large-scale
circulation, most importantly in the mean zonal wind, which facilitate
vertical wave propagation by allowing for a greater portion of gravity
wave harmonics originated in the lower atmosphere to avoid filtering on
their way to upper layers.