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Modelling

Global 3D modeling of the atmosphere of Mars

GEM-Mars is a 3D general circulation model (GCM) for the atmosphere of Mars which describes the meteorology, circulation, dust, clouds, water, polar caps, radiation, and atmospheric chemistry from the surface up to 170 km altitude.

It applies the dynamical core of the Global Environmental Multiscale model (GEM) which is the standard weather forecast model of Environment Canada.

A full description and evaluation of the model can be found in Neary and Daerden, 2018. A more detailed evaluation of atmospheric chemistry simulations is presented in Daerden et al., 2019.

At BIRA-IASB, GEM-Mars simulations are used in the data retrieval process for the NOMAD instrument (Vandaele et al., 2018) on board the ESA-Roscosmos ExoMars Trace Gas Orbiter (TGO). TGO has been observing the Mars atmosphere from orbit since the start of science operations in March 2017. First results were published in Vandaele et al., 2019 and Korablev et al., 2019.

We have used the GEM-Mars model to perform an ensemble of simulations of the Martian atmosphere, using stochastic gas release scenarios to identify a potential source region of methane east of Gale Crater. (Independent confirmation of a methane spike on Mars and a source region east of Gale Crater. Nature Geoscience, April 2019.)

Other applications of GEM-Mars include:

  • Saltation under Martian gravity conditions and its influence on the global dust distribution (Musiolik et al., 2018)
  • The climatology of carbon monoxide and water vapor on Mars (Smith et al., 2018)
  • Two test-cases for synergistic detections in the Martian atmosphere: Carbon monoxide and methane (Robert et al., 2017)
  • Formation of layers of methane in the atmosphere of Mars after surface release (see animation below) (Viscardy et al., 2016)
  • A solar escalator on Mars: Self-lifting of dust layers by radiative heating (see images below) (Daerden et al., 2015)

 

The animation above shows the simulation of a plume of methane released from Nili Fossae just before the northern hemisphere autumn (around Ls = 150). After around 10 martian days (or sols), the plume has encircled the globe and formed a layer at around 20 km height. After 20 sols, the methane is dispersing but a layer is still visible above 40 km. (Simulation data from Viscardy et al., 2016)

 

The GCM simulates temperature and water ice clouds. This animation shows the evolution during one Mars day (called a sol) during the Martian northern spring/summer period. The colours indicate temperatures ranging from approximately -170C (blue) to -10C (red) on the surface and in a vertical slice along the equator. Clouds are represented by the white isosurfaces, and can be seen forming over the mountains at night.

 

The GEM-Mars model has been used to examine dust in the Mars atmosphere as observed with the LIDAR instrument on the Phoenix lander. Back trajectories calculated from the model show that the air parcel measured had previously passed through a dust cloud. The model simulations showed that the air was ascending under the influence of the solar radiation heating up the dust in the air parcel, a process call a "solar escalator" that was previously observed on Earth as well. (From Daerden et al., 2015)

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