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Tuesday 11 Oct 2022A multiannual record of convective instability in Mars's middle atmosphere

Nick Heavens -

Harrison 170 14:30-15:30

Gravity waves transfer energy and momentum from the lower to the middle and upper atmospheres of both Earth and Mars. Momentum transfer can occur through the wave dissipative process of saturation associated with convective, shear, or other types of instability. Gravity wave saturation both impacts the atmospheric circulation where saturation occurs and also mediates the gravity wave flux above the level of saturation. Convective instabilities have been observed in Mars's middle atmosphere for almost 50 years, but the need for systematic observation only has become pressing recently as global climate models of Mars have begun to incorporate gravity wave parameterisations of varying complexity. This talk will focus on my recent work to characterize the seasonal, interannual, and dust storm event-driven variability in convective instability in Marsís middle atmosphere from satellite observations. This survey strongly suggests that gravity waves interacting with thermal inversions and/or strong tidal modes create convective instabilities about 1% of the time in particular zones of the middle atmosphere. But during Marsís continental to planetary-scale dust events, strengthened tides and thermal inversions and/or stronger gravity wave flux drive a much higher frequency of convective instability in these zones, suggesting gravity wave drag plays an outsized role in the general circulation during dust events. The survey also provides more direct quantitative constraints on gravity wave parameterisations for Mars than previously possible.

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