On the other hand, the major factor which governs the
variability in the Martian
atmosphere is the amount and distribution of suspended dust.
Because of this variability, and since even for a given year the details
of the dust distribution and optical properties can be uncertain,
multi-annual model integrations were carried out for the database
assuming various ``dust scenarios'', i.e. prescribing various amount
of airborne dust in the simulated atmosphere.
4 dust scenarios are proposed :
Five dust scenarios have been used :
- A first scenario, named ``Martian Year 24" (MY24)
was designed to
mimic Mars as
observed by Mars Global Surveyor in between 1999 to june 20011, a martian
year though to be typical.
The dust fields were derived from MGS TES observations using data
assimilation technique. The MY24 scenario is provided with 3 solar EUV
conditions: solar min, solar ave, solar max.
- The cold scenario corresponds to an extremely clear
atmosphere (``Low dust scenario"; dust opacity
), topped with
a solar
minimum thermosphere.
- The warm scenario corresponds to "dusty atmosphere for the
season" scenario (but not a global dust storm), topped with a solar
maximum thermosphere.
- The dust storm scenario (
)
represents Mars during a global dust storm (dust
opacity set to 4). Only available when such storms are likely to happen,
during northern fall and winter (Ls=180-360), but with with 3 solar EUV
conditions: solar min, solar ave, solar max.
The ``cold'' and ``warm'' annual
scenarios are provided to bracket the possible global conditions
on Mars outside global dust storms which are thought to
be highly variable locally and from year to year.