Geoscience Reference
In-Depth Information
Table 1.
Z
0
)andthe
original dust-emission reduction factor (ADAM) and the modified value (ADAM2) in
the ADAM model.
USGS vegetation categories with the surface roughness length (
Reduction factor (
R
)
Z
0
Type
Description
(m)
ADAM
ADAM2
A
1
Urban and Built-up land
1.00
1.0
—
B
2
Dry Cropland and Pasture
0.02
0.4
0.9
C
3
Irrigated Cropland and Pasture
0.02
0.6
0.8
D
4
Mixed Dry/Irrigated Cropland and Pasture
0.02
0.5
0.8
E
5
Cropland/Grassland
0.02
0.5
0.9
F
6
Cropland/Woodland
0.02
0.7
0.8
G
7
Grassland
0.02
0.6
0.9
H
8
Shrubland
0.03
0.7
0.8
I
9
Mixed Shrub/Grassland
0.03
0.75
0.8
J
10
Savanna
0.02
0.8
—
K
11
Deciduous Broad leaf Forest
0.05
0.9
—
L
12
Deciduous Needle leaf Forest
0.05
0.9
—
M
13
Evergreen Broad leaf Forest
0.05
0.9
—
N
14
Evergreen Needle leaf Forest
0.05
0.9
—
O
15
Mixed Forest
0.05
0.9
—
P
16
Water
0.001
1.0
—
Q
17
Herbaceous Wet land
0.002
1.0
—
R
18
Wooded Wet land
0.003
1.0
—
S
19
Barren or sparsely vegetated land
0.01
0.1
0.2
T
20
Herbaceous Tundra
0.003
1.0
—
U
21
Wooded Tundra
0.003
1.0
—
V
22
Mixed Tundra
0.002
1.0
—
W
23
Bare ground Tundra
0.001
1.0
—
X
24
Snow or Ice
0.001
1.0
—
with observations, suggesting that some improvement in the specification
of the dust emissions in the source region is required.
This discrepancy might have arisen due to the change in surface con-
ditions in the source region. The maximum dust concentration in Fig. 2
is associated with the dust storms that occurred in central northern China
and eastern Inner Mongolia. To examine this discrepancy, we have analyzed
precipitation amount in the northwestern central part of China (Region 1
in Fig. 1) and the eastern part of Inner Mongolia (Region 2 in Fig. 1).
Table 2 shows the annual total precipitation amount in Regions 1 and 2
from 1998 to 2004. Since 1998, the annual total precipitation amount in
Region 1 decreased to a minimum value of 44.8 mm in 2001 with a slight
increase thereafter and the annual total precipitation amount in Region 2
decreased remarkably from 1999 to a minimum value of 265 mm in 2001,
