Surface Warming During the 2018/Mars Year 34 Global Dust Storm.

The impact of Mars's 2018 Global Dust Storm (GDS) on surface and near-surface air temperatures was investigated using an assimilation of Mars Climate Sounder observations. Rather than simply resulting in cooling everywhere from solar absorption (average surface radiative flux fell 26 W/m2), the globally averaged result was a 0.9-K surface warming. These diurnally averaged surface temperature changes had a novel, highly nonuniform spatial structure, with up to 16-K cooling/19-K warming. Net warming occurred in low thermal inertia regions, where rapid nighttime radiative cooling was compensated by increased longwave emission and scattering. This caused strong nightside warming, outweighing dayside cooling. The reduced surface-air temperature gradient closely coupled surface and air temperatures, even causing local dayside air warming. Results show good agreement with Mars Climate Sounder surface temperature retrievals. Comparisons with the 2001 GDS and free-running simulations show that GDS spatial structure is crucial in determining global surface temperature effects.