Water Vapor Vertical Profiles on Mars in Dust Storms Observed by TGO/NOMAD
Date Issued
2019
Author(s)
Aoki, S.
•
Vandaele, A. C.
•
Daerden, F.
•
Villanueva, G. L.
•
Liuzzi, G.
•
Thomas, I. R.
•
Erwin, J. T.
•
Trompet, L.
•
Robert, S.
•
Neary, L.
•
Viscardy, S.
•
Clancy, R. T.
•
Smith, M. D.
•
Lopez‐Valverde, M. A.
•
Hill, B.
•
Ristic, B.
•
Patel, M. R.
•
•
Lopez‐Moreno, J.‐J.
•
Abstract
It has been suggested that dust storms efficiently transport water vapor from the near-surface to
the middle atmosphere on Mars. Knowledge of the water vapor vertical profile during dust
storms is important to understand water escape. During Martian Year 34, two dust storms
occurred on Mars: a global dust storm (June to mid-September 2018) and a regional storm
(January 2019). Here we present water vapor vertical profiles in the periods of the two dust
storms (Ls=162–260° and Ls=298–345°) from the solar occultation measurements by Nadir and
Occultation for Mars Discovery (NOMAD) onboard ExoMars Trace Gas Orbiter (TGO). We
show a significant increase of water vapor abundance in the middle atmosphere (40–100 km)
during the global dust storm. The water enhancement rapidly occurs following the onset of the
storm (Ls~190°) and has a peak at the most active period (Ls~200°). Water vapor reaches very
high altitudes (up to 100 km) with a volume mixing ratio of ~50 ppm. The water vapor
abundance in the middle atmosphere shows high values consistently at 60°S-60°N at the growth
phase of the dust storm (Ls=195-220°), and peaks at latitudes greater than 60°S at the decay
phase (Ls=220–260°). This is explained by the seasonal change of meridional circulation: from
equinoctial Hadley circulation (two cells) to the solstitial one (a single pole-to-pole cell). We also
find a conspicuous increase of water vapor density in the middle atmosphere at the period of the
regional dust storm (Ls=322–327°), in particular at latitudes greater than 60°S.
Volume
124
Issue
12
Start page
3482
Issn Identifier
2169-9097
Ads BibCode
2019JGRE..124.3482A
Rights
open.access
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