Geology Reference
In-Depth Information
Atmospheric Interaction with Two-dimensional Mountain Ranges
Nh/U << 1; elongate range (
β
>>1)
Nh/U >> 1; elongate range (
β
>>1)
no rotation
no rotation
Fig. 11.25
Interaction of incoming
moisture with a two-dimensional
mountain range.
Diagrams depicting the roles of the non-
dimensional number
Nh
/
U
, range symmetry
b
,
and rotation of winds due to Coriolis effects
on the pattern of precipitation associated with
a mountain range. Changes in the ratio
(
Nh
/
U
) of relief (
h
) to wind speed (
U
) are
reflected in the degree of blocking of the flow
(A versus B). Changes in range symmetry (
b
)
govern the likelihood of flow splitting
(A versus C). Coriolis-induced rotation
(B versus D) moves the maximum of
precipitation off the axis of topographic
symmetry. Modified after Galewsky (2009).
A
B
Symmetrical range
(β
= 1
)
Nh/U >> 1; elongate range
(
β
>>1)
with rotation
C
D
Weather Forecasting Models, WRF
80
80
3-km resolution
1-km resolution
70
70
60
60
50
50
40
40
30
30
20
20
10
10
0
0
Fig. 11.26
Use of research-grade Weather Research and Forecasting (WRF) models.
A WRF model run at 3 km (left) and at 1 km (right) resolution during a storm event on 4-7 May 2008. Contours
represent total precipitation (mm) since the beginning of simulation. Shades (colors) depict precipitation up to hour
72 (3 km run) and hour 60 (1 km run). Note the significant difference in precipitation pattern between the 3 km
simulation and the higher-resolution 1 km run. In addition, the temperature at the time of precipitation is very near
0
°
C in the Bighorn Range, while it is −10
°
C in the Wind River Range, thereby suggesting a rain-snow mix in the
Bighorns and dry snow in the Wind Rivers. Figures courtesy of Gary Clow, US Geological Survey. [A color version of
this figure appears as Plate 11.]
