Parameterization of Rocket Dust Storms on Mars in the LMD Martian GCM: Modeling Details and Validation

Abstract

The origin of the detached dust layers observed by the Mars Climate Sounder aboard the Mars Reconnaissance Orbiter is still debated. Spiga et al. (2013, https://doi.org/10.1002/jgre.20046) revealed that deep mesoscale convective “rocket dust storms” are likely to play an important role in forming these dust layers. To investigate how the detached dust layers are generated by this mesoscale phenomenon and subsequently evolve at larger scales, a parameterization of rocket dust storms to represent the mesoscale dust convection is designed and included into the Laboratoire de Météorologie Dynamique (LMD) Martian Global Climate Model (GCM). The new parameterization allows dust particles in the GCM to be transported to higher altitudes than in traditional GCMs. Combined with the horizontal transport by large‐scale winds, the dust particles spread out and form detached dust layers. During the Martian dusty seasons, the LMD GCM with the new parameterization is able to form detached dust layers. The formation, evolution, and decay of the simulated dust layers are largely in agreement with the Mars Climate Sounder observations. This suggests that mesoscale rocket dust storms are among the key factors to explain the observed detached dust layers on Mars. However, the detached dust layers remain absent in the GCM during the clear seasons, even with the new parameterization. This implies that other relevant atmospheric processes, operating when no dust storms are occurring, are needed to explain the Martian detached dust layers. More observations of local dust storms could improve the ad hoc aspects of this parameterization, such as the trigger and timing of dust injection.

Martian dust storm impact on atmospheric H2O and D/H observed by ExoMars Trace Gas Orbiter

“…Detached dust layers were previously identified on many occasions [14][15][16] , and their existence has been explained by uplifting during strong convection processes [17][18][19][20] . Water ice clouds may be responsible for some of the observed layers, as indicated by observations at other wavelengths and by previous investigations [21][22][23] .…”

Dust tides and rapid meridional motions in the Martian atmosphere during major dust storms

“…Simulations suggested that thermal tides can enhance the net meridional transport of aerosols through momentum flux divergence via tidal dissipation 46 . According to recent observational and numerical studies, the dusty deep convection becomes more widespread in the mid-latitudes under dust storm conditions 45,47 . It should be noted that in the period from noon to the early afternoon, when dusty deep convection is expected to be the strongest, the water vapor is retreating to higher latitudes from the equatorial region ( Supplementary Fig.…”

Explanation for the increase in high altitude water on Mars observed by NOMAD during the 2018 global dust storm

“…This may indicate that there are missing processes in the GCM that relate to daytime activity, e.g. sub grid-scale deep convective events that are currently not represented in the model [Spiga et al, 2013;Daerden et al, 2015;Wang et al, 2018;Heavens et al, 2018]. To impose control over the vertical profile, we use a prescribed distribution based on Conrath [1975] (also see Montmessin et al, [2004] for the equations).…”

“…This layer is difficult to implement using a simple Conrath description and was not considered in our simulations. In reality it may be caused by non-local deep convective events when the GDS develops [Spiga et al, 2013;Wang et al, 2018;Heavens et al, 2018].…”