The Roles of Latent Heating and Dust in the Structure and Variability of the Northern Martian Polar Vortex

E. R. Ball, D. M. Mitchell, W. J. M. Seviour, S. I. Thomson, G. K. Vallis

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Abstract

The winter polar vortices on Mars are annular in their potential vorticity (PV) structure, a phenomenon identified in observations, reanalysis, and some numerical simulations. Some recent modeling studies have proposed that condensation of atmospheric carbon dioxide at the winter pole is a contributing factor to maintaining the annulus through the release of latent heat. Dust and topographic forcing are also known to be causes of internal and interannual variability in the polar vortices. However, coupling between these factors remains uncertain, and previous studies of their impact on vortex structure and variability have been largely limited to a single Martian global climate model (MGCM). Here, by further developing a new MGCM, we decompose the relative roles of latent heat, topography, and dust as drivers for the variability and structure of the northern Martian polar vortex. Additionally, we analyze a reanalysis data set, finding that there are significant differences in vortex morphology and variability according to the spacecraft instrument used for the data assimilation. In both model and reanalysis, high atmospheric dust loading (such as that seen during a global dust storm) can disrupt the vortex, cause the destruction of PV in the low-to-mid-altitudes (>0.1 hPa), and significantly reduce spatial and temporal vortex variability. Through our simulations, we find that the combination of dust and topography primarily drives the eddy activity throughout the Martian year, and that although latent heat release can produce an annular vortex, it has a relatively minor effect on vortex variability.
Original languageEnglish
Article number203
Number of pages16
JournalPlanetary Science Journal
Volume2
Issue number5
Early online date24 Sep 2021
DOIs
Publication statusPublished - Oct 2021

Bibliographical note

Funding Information:
OpenMARS data can be found in Holmes et al. (2019). EMARS data are available at https://doi.org/10.18113/ D3W375. The data derived from OpenMARS, EMARS, and Isca simulations and used to plot the figures within this paper are available from the University of Bristol data repository: doi:10.5523/bris.3i92ii47fndkv2scy9jgrteg0x. We would also like to thank the creators of the MCD for freely distributing the database. The MCD dust products used within this study are available at http://www-Mars.lmd.jussieu.fr/Mars/info_web/ index.html; see Madeleine et al. (2011) for details. E.B. is funded by an NERC GW4+ Doctoral Training Partnership studentship from the Natural Environmental Research Council (NE/S007504/1). D.M. is funded under an NERC research fellowship (NE/N014057/1). Finally, we also thank the editor and two anonymous reviewers for their invaluable comments.

Publisher Copyright:
© 2021. The Author(s). Published by the American Astronomical Society.

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