The impact of a realistic vertical dust distribution on the simulation of the Martian General Circulation

Abstract

AbstractLimb‐scanning observations with the Mars Climate Sounder and Thermal Emission Spectrometer (TES) have identified discrete layers of enhanced dust opacity well above the boundary layer and a mean vertical structure of dust opacity very different from the expectation of well‐mixed dust in the lowest 1–2 scale heights. To assess the impact of this vertical dust opacity profile on atmospheric properties, we developed a TES limb‐scan observation‐based three‐dimensional and time‐evolving dust climatology for use in forcing general circulation models (GCMs). We use this to force the MarsWRF GCM and compare with simulations that use a well‐mixed (Conrath‐ν) vertical dust profile and Mars Climate Database version 4 (MCD) horizontal distribution dust opacity forcing function. We find that simulated temperatures using the TES‐derived forcing yield a 1.18 standard deviation closer match to TES temperature retrievals than a MarsWRF simulation using MCD forcing. The climatological forcing yields significant changes to many large‐scale features of the simulated atmosphere. Notably the high‐latitude westerly jet speeds are 10–20 m/s higher, polar warming collar temperatures are 20–30 K warmer near northern winter solstice and tilted more strongly poleward, the middle and lower atmospheric meridional circulations are partially decoupled, the migrating diurnal tide exhibits destructive interference and is weakened by 50% outside of equinox, and the southern hemisphere wave number 1 stationary wave is strengthened by up to 4 K (45%). We find the vertical dust distribution is an important factor for Martian lower and middle atmospheric thermal structure and circulation that cannot be neglected in analysis and simulation of the Martian atmosphere.