Martian Year 34 Column Dust Climatology from Mars Climate Sounder Observations: Reconstructed Maps and Model Simulations. Issue 8 (20th August 2020)

• Record Type: Journal Article
• Authors: Montabone, Luca; Spiga, Aymeric; Kass, David M.; Kleinböhl, Armin; Forget, François; Millour, Ehouarn
• Is Part Of: Journal of geophysical research. Volume 125:Issue 8(2020)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2020-08-20
• Subjects: Mars atmosphere -- Column dust optical depth -- Dust storm -- Global Dust Event -- Dust scenario -- Mars Climate Sounder; Planets -- Periodicals; Geophysics -- Periodicals; 559.9
• DOI: 10.1029/2019JE006111
• Languages: English
• ISSNs: 2169-9097

Abstract

Abstract: We have reconstructed longitude‐latitude maps of column dust optical depth (CDOD) for Martian year (MY) 34 (5 May 2017– 23 March 2019), using observations by the Mars Climate Sounder (MCS) aboard NASA's Mars Reconnaissance Orbiter spacecraft. Our methodology works by gridding a combination of standard (v5.2) and novel (v5.3.2) estimates of CDOD from MCS limb observations, using an improved "Iterative Weighted Binning." In this work, we have produced four gridded CDOD maps per sol, at different Mars Universal Times. Together with the seasonal and daily variability, the use of several maps per sol also allows us to explore the diurnal variability of CDOD in the MCS dataset, which is shown to be particularly strong during the MY 34 equinoctial global dust event (GDE). In order to understand whether the diurnal variability of CDOD has a physical explanation, and examine the impact of the MY 34 GDE on some aspects of the atmospheric circulation, we have carried out numerical simulations with the "Laboratoire de Météorologie Dynamique" Mars Global Climate Model. We show that the model is able to account for at least part of the observed CDOD diurnal variability. This is particularly true in the southern hemisphere where a strong diurnal wave at the time of the GDE is able to displace dust horizontally as well as vertically. The simulations also clearly show the impact of the MY 34 GDE on the mean meridional circulation and the super‐rotating equatorial jet, similarly to the effects of the equinoctial GDE in MY 25. Plain Language Summary: Large dust storms on Mars have dramatic impacts on the entire atmosphere but may also have critical consequences for robotic and future human missions. Therefore, there is compelling need to produce an accurate reconstruction of their spatial and temporal evolution for a variety of applications, including to guide Mars climate model simulations. The Martian year 34 (5 May 2017–23 March 2019) represents a very interesting case because an extreme dust event occurred near the time of the northern autumn equinox, consisting of multiple large dust storms engulfing all longitudes and most latitudes with dust for more than 150 Martian days ("sols"). We have used satellite observations from the Mars Climate Sounder instrument aboard NASA's Mars Reconnaissance Orbiter to reconstruct longitude‐latitude maps of the opacity of the atmospheric column due to the presence of dust at several times in each sol of Martian year 34. These maps allow us to analyze the seasonal, day‐to‐day, and day‐night variability of dust in the atmospheric column, which is particularly intense during the extreme dust event. We have also used simulations with a Mars climate model to show that the strong day‐night variability may be partly explained by the large‐scale circulation. Key Points: We reconstruct subdaily maps of column dust optical depth for Martian year 34 to be used for data analysis and modeling We observe seasonal, daily, and diurnal variability in the column dust, notably during the global dust event (GDE) Simulations with a global climate model examine the impact of the GDE on the atmospheric circulation and diurnal variability of column dust