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In dust-free case, the surface stress associated with km-size thermal
convection frequently reaches 0.04 Pa in the afternoon when the
km-size convection is well developed (Figure 5).
The surface stress in the afternoon exceeds the threshold value
required to raise dust from the surface if the large scale
background wind can be superposed on the convective wind (Figure 6).
The large scale background wind should be considered to occur dust
injection from the surface to atmosphere self-consistently
in our numerical model.
However, when dust injection can be represent self-consistently in our
numerical model by introducing large scale background wind, the
circulation structure of km-size thermal convection will be
affected by not only dust but also the background wind.
It is prefer to exclude the influence of background wind from the
simulation results in dusty case because the effect of dust on
km-size thermal convection is one of our interests in this study.
Therefore, we do not consider large scale background wind but reduce
the value of threshold surface stress in our model so that dust
injection occurs in the afternoon when the km-size thermal is well
developed.
The threshold surface stress is set to be 0.01 Pa.
This value is based on the results of dust-free case that the value of
surface stress frequently exceeds 0.01 Pa at several grid point
in the afternoon (Figure 6).
Initial distribution of wind, pressure and temperature are that of
dust-free condition at LT=6:00 of 6rd days.
The numerical integration is performed for 6 days.
Figure 9 shows time development of horizontal mean
dust opacity for solar radiation (λ = 0.67 μm).
The dust opacity rapidly increase on the first day and keep almost
constant value (τ ˜ 0.07) after that.
In following sections, we show a feature of dust mixing associated
with the km-size thermal convection from the first to second day
and resluts on the 6th day when the model atmosphere achieves an
energetic equilibrium state on the time scale of diurnal change.
- Feature of dust mixing
- Horizontal mean fields
- Circulation structure of the convection
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Figure 9: Time development of horizontal mean dust opacity for
solar radiation (λ = 0.67 μm).
The horizontal axis is numerical integration time.
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