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4.a. Feature of dust mixing (2)
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Figure 10b:
Dust mixing of the second day after the switch-on of dust
injection.
Results of every 1 hour from LT = 07:00 to 18:00 are
shown.
(Upper panel) Mixing ratio of dust (kg/kg).
Areas of the value of dust mixing ratio larger than
1.0×10-8 are
colored.
(Lower panel) Turbulent diffusion coefficient.
Areas of the value larger than
1.0×10-5 are
colored.
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Dust, which has been mixed and spread up to about 10 km height,
is further transported upward into the stratosphere.
Figure 10b (upper panel) shows the
distribution of dust mixing ratio of the second day
after the switch-on of dust injection.
In the afternoon at the altitudes of around 10 km height,
dust moves upward taking the form of plumes.
The distribution of turbulent diffusion coefficient
(Figure 10b (lower panel))
suggests
that these plumes are
accompanied with
a vertical mixing process which is different from the
km-size thermal convection near the surface.
The vertical mixing of those altitudes is caused by the
vertical difference of radiative heating associated with
the vertical contrast of dust density.
As a result of dust injection and mixing of the first day,
a region with a large vertical gradient of dust mixing ratio
forms at the altitudes from 11 to 13 km height
(Figure 11a).
Associated with this,
there appears large difference of
solar radiative heating between the
regions below and above the height of around 11 to 13 km
(Figure 11g,
Figure 11h).
Consequently,
inversion of potential temperature occurs between the
levels of about 10km height and above,
and the layer becomes convectively unstable.
The vertical distribution of
the horizontal mean potential temperature
(Figure 11d (right
panel))
shows that
the unstable layer is rapidly stabilized and
potential temperature of
the altitudes from 10 to 15 km becomes
vertically uniform.
The upward transport of dust into the stratosphere
is a direct result of the heating of dust solar
absorption;
dust is no longer a passive tracer in this region.
The vertical profile of horizontal mean dust mixing ratio
does not change greatly at the 4th day and after
(Figure 11b).
In the convection layer,
dust mixing ratio slightly increases as the depth of
the convection layer decreases.
In the region above the convection layer,
dust mixing ratio slightly decreases
because of the gravitational sedimentation of dust.
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