Geoscience Reference
In-Depth Information
Table 2.
Details of the HIRES atmospheric model used for this study.
Model feature
HIRES
Horizontal resolution
15 km
Numerical scheme
Split semi-implicit (high order)
No. of vertical levels
34
Assimilation scheme
6-hourly cycling
Initialization
Dynamic
Orography
2 min resolution
Boundary layer scheme
Mellor-Yamada, Level 2.25
Radiation scheme
Fels-Schwarzkopf
Convective scheme
Kain-Fritsch
Sea-surface temperatures
5-day average
Lateral boundary conditions
From BMRC LAPS model
deposition. These changes are discussed by Irannejad and Shao,
9
Lu and
Shao
4
and especially by Shao.
10
The wind erosion scheme is described in
detail by Shao
et al.
5
The scheme tracks the history of various particle
sizes and the output we are interested in for this study is the total dust
concentration, which is the sum of the concentrations of all the dust parti-
cle sizes considered in the scheme. As in the study by Shao
et al.
,
5
we used
three dust particle sizes, and therefore calculated the temporal and spatial
evolution of the three particle concentration terms
c
1
c
2
,and
c
3
that con-
tribute additively to the total dust concentration, one concentration term
from each of the particle sizes. The particle sizes,
d
i
,were
d
1
<
2
µ
m;
2
µ
m
≤
d
2
≤
11
µ
m; and 11
µ
m
≤
d
3
≤
22
µ
m.
5. Results and Discussion
For the modeling case studies, satellite imagery indicating suspended dust
provides the best available verification, for Australia, of the aerial extent
of dust. Dust areas in these satellite images can be compared to the model
predicted wind fields for the same time to provide verification of the model.
Multi-spectral satellite techniques rely principally on differences in absorp-
tion and radiation between water/ice and dust in key infrared bands. The
satellite images used for highlighting the dust areas were generated using
GOES-9 imagery in the Bureau of Meteorology by the 11-12
µ
m “split-
window” or “reverse absorption” algorithm that is used to identify volcanic
ash.
11
,
12
This technique uses the different absorption characteristics of dust
