Geoscience Reference
In-Depth Information
a forcing term to the vertical momentum equation at updraft grid points.
This term is referred to as subgrid-scale updraft acceleration (SUA), and
is given by
2
3
e,
dw
dt
1
τ
=
(1)
SUA
where
w
is vertical velocity,
e
is TKE, and
τ
is the timescale for the updraft
acceleration. By trial and error we set
τ
= 10 min. Although this forcing
term is solely artificial, it is at least useful to examine the effects of turbulent
intensity and hence to give an idea for the parameterization of convection
effects in dust transport simulations.
Figure 6 shows the time-height section of TKE in the case of ∆
x
=
4 km with SUA. The result significantly improves the boundary-layer
development looks quite similar to that seen in the finer-grid cases (compare
with Figs. 2(b) and 5).
Fig. 6. The same as Fig. 4, except for TKE in the case of ∆
x
= 4 km with subgrid-scale
updraft acceleration.
