JpGU-AGU Joint Meeting 2020

Presentation information

[E] Oral

M (Multidisciplinary and Interdisciplinary) » M-IS Intersection

[M-IS07] Aqua planetology

convener:Yasuhito Sekine(Earth-Life Science Insitute, Tokyo Institute of Technology), Hidenori Genda(Earth-Life Science Institute, Tokyo Institute of Technology), Keisuke Fukushi(Institute of Nature & Environmental Technology, Kanazawa University), Tomohiro Usui(Japan Aerospace Exploration Agency)

[MIS07-03] Explanation for the increase in high altitude water on Mars observed by NOMAD during the 2018 global dust storm

*Lori Neary1, Frank Daerden1, Shohei Aoki1, James Whiteway2, Robert Todd Clancy3, Michael Smith4, Sébastien Viscardy1, Justin Tyler Erwin1, Ian Thomas1, Geronimo Villanueva4, Giuliano Liuzzi4, Matteo Crismani5, Michael Wolff3, Stephen Lewis6, James Holmes6, Manish Patel6, Marco Giuranna7, Cedric Depiesse1, Arianna Piccialli1, Séverine Robert1, Loic Trompet1, Yannick Willame1, Bojan Ristic1, Ann Carine Vandaele1 (1.Royal Belgian Institute for Space Aeronomy, Brussels, BE, 2.Centre for Research in Earth and Space Science, York University, Toronto, ON, CA, 3.Space Science Institute, Boulder, CO, USA, 4.NASA Goddard Space Flight Center, Greenbelt, MD, USA, 5.NPP/USRA, NASA Goddard Space Flight Center, Planetary Systems Laboratory, Code 693, Greenbelt, MD, USA, 6.School of Physical Sciences, The Open University, Milton Keynes, UK, 7.Instituto di Astrofisica e Planetologia Spaziali, Instituto Nazionale di Astrofisica, Rome, IT)

Keywords:Mars, Global circulation modelling, water vapor, water ice clouds, atmospheric escape

Using the GEM-Mars three-dimensional general circulation model (GCM) (Neary and Daerden, 2018), we examine the mechanism responsible for the enhancement of water vapour in the upper atmosphere as measured by the Nadir and Occultation for MArs Discovery (NOMAD) instrument on board ExoMars Trace Gas Orbiter (TGO) during the 2018 global dust storm on Mars (Aoki et al., 2019).

GCM experiments with different prescribed vertical profiles of dust show that when more dust is present higher in the atmosphere, the temperature increases and the amount of water ascending over the tropics is not limited by saturation until reaching heights of 70-100 km. The warmer temperatures allow more water to ascend to the mesosphere. The simulation of enhanced high-altitude water abundances is very sensitive to the vertical distribution of the dust prescribed in the model (Neary et al., 2019).

The GEM-Mars model includes gas-phase photochemistry, and these simulations show how the increased water vapour over the 40-100 km altitude range results in the production of high-altitude atomic hydrogen which can be linked to atmospheric escape. The figure below shows the ratio of results from two simulations, GDS0008 (with a dust vertical profile corrected to be similar to observations) and nonGDS (no correction to dust profile) for water vapor and hydrogen volume mixing ratios in the equatorial region (between 30N/S) for the period between Ls = 160-280. At the onset of the global dust storm, the water vapor profile responds with a large increase by more than a factor of 150 at a height of around 70 km. At this altitude, the photolysis of water vapor is strong, and atomic hydrogen is produced. After several sols, an increase in hydrogen is seen.