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| Titel |
An atmospheric process to explain the formation of the detached layers of dust on Mars: GCM modelling, validation and comparison with observations |
| VerfasserIn |
Chao Wang, Tanguy Bertrand, François Forget, Aymeric Spiga, Ehouarn Millour |
| Konferenz |
EGU General Assembly 2015
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 17 (2015) |
| Datensatznummer |
250112888
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| Publikation (Nr.) |
 EGU/EGU2015-13075.pdf |
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| Zusammenfassung |
| Dust is the crucial component of the Martian atmosphere. Its motion, horizontal and vertical
transportation, is of great importance to Martian meteorology and climate. Recently, detached
layers of dust are confirmed by the observations of the Mars Climate Sounder (MCS) as well
as the Thermal Emission Spectrometer (TES). The origin of the detached layers has remained
debated. They cannot be reproduced by traditional Global Climate Models (GCM) including
a dust cycle.
Several possible interpretations were proposed to explain the origins of the detached
layers of dust, such as small-scale dust lifting, upslope topographic winds, scavenging by
water ice clouds, dust storms/¦ Scavenging has been shown to be unable to form of dust
detached layer through the simulations using the GCM developed at the Laboratoire de
Météorologie Dynamique (LMD).
In the present study, a new parameterization called “rocket dust storms” in the LMD
Martian GCM were implemented on the basis of mesoscale model simulations. The
parameterization works like this: In the GCM, when a strong dust opacity gradient is
observed, a local (subgrid scale) dust storm will be produced. Because of the difference of
radiative heating rates between inside and outside of the dust storm, the dust particles inside
the dust storm will be transported to high altitudes due to the vertical velocity of the dust
which is directly deduced from the extra dust radiative heating, since we have found that this
heating is almost integrally converted to adiabatic heating . The dust particles injected in
the high layers are then horizontally transported by the large scale winds in the
GCM.
In the present study, the validation of the “rocket dust storm” parameterization and the
comparison between model outputs and MCS observations is implemented. To do so, case
studies of the dust storm are performed to see how the dust were lifted and transported and
how the detached layers formed in the upper atmosphere. We find that the detached layers of
dust can be easily recognized in the model outputs. This illustrates that the “rocket dust
storms” parameterization yields satisfying results in the GCM and it could be the origin of the
formation of detached layers of dust on Mars. The diurnal and seasonal variations
between model and MCS observations are also compared. The detached layers
of dust obtained by the model reach an agreement with the MCS observations. |
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