Preprints
https://doi.org/10.5194/gmd-2016-241
https://doi.org/10.5194/gmd-2016-241

Submitted as: methods for assessment of models 16 Nov 2016

Submitted as: methods for assessment of models | 16 Nov 2016

Review status: this preprint was under review for the journal GMD but the revision was not accepted.

An intercomparison of Large-Eddy Simulations of the Martian daytime convective boundary layer

Tanguy Bertrand1, Aymeric Spiga1, Scot Rafkin2, Arnaud Colaitis1, François Forget1, and Ehouarn Millour1 Tanguy Bertrand et al.
  • 1Laboratoire de Météorologie Dynamique (UPMC/CNRS), Paris, France
  • 2SouthWest Research Institute, Boulder, CO, USA

Abstract. Large-Eddy Simulations (LES) for Mars resolve the Planetary Boundary Layer (PBL) turbulent dynamics by using a very fine horizontal resolution of a few tens of meters. LES modeling is becoming a more and more useful tool to prepare the robotic exploration of Mars by providing means to evaluate the intensity of convective plumes and vortices, horizontal wind gustiness, and turbulent fluctuations of temperature in the Martian PBL. In such context, and given the relative paucity of turbulence-related measurements on Mars, an intercomparison of LES models is a fruitful way to evaluate the models' predictions and to indicate possible areas of improvement. Thus, to prepare the landing of the ExoMars Schiaparelli lander (also named ExoMars Demonstrator Module, EDM), scheduled for October 2016, the results of the Laboratoire de Météorologie Dynamique (LMD) and South-West Research Institute (SwRI) LES models have been compared. The objective of this study is to determine the range of uncertainties, and dispersions, of the two numerical models' predictions, for the critical phase of the spacecraft's descent in the Martian daytime turbulent PBL. First, a strategy is defined to ensure similar radiative forcing in both the LMD and SwRI models. Then, LES are performed over a flat terrain with and without large-scale ambient horizontal wind. The LMD and SwRI Martian LES models predict similar temporal evolution of the PBL and organization in the horizontal and vertical wind fields. However, the convective motions in the daytime PBL are more vigorous by a factor 1.5–2 in SwRI results than in LMD results, independently of the presence or not of ambient horizontal wind. This discrepancy is further investigated through sensitivity studies to surface conditions, ambient wind, and airborne dust loading.

Tanguy Bertrand et al.

 
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Status: closed
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Tanguy Bertrand et al.

Tanguy Bertrand et al.

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Short summary
We compare the results of two numerical models which simulate the Martian atmospheric turbulence in the first km above the surface, using for both similar forcings. This intercomparison is a fruitful way to evaluate the models' predictions and to indicate possible areas of improvement, thus preparing for future martian missions. Although the model predict similar evolution of the turbulence in the lower atmosphere, the intensity of the processes differ by a factor of 1.5–2.