Geography Reference
In-Depth Information
For steady flow, (7.99) has a solution with complex amplitude
f
0
h
0
/
H
K
2
iε
K
s
ψ
0
=
−
−
(7.100)
rK
2
(ku)
−
1
. Thus, boundary layer drag shifts the phase of the response
and removes the singularity at resonance. However, the amplitude is still a max-
imum for K
where ε
≡
K
s.
and the trough in the streamfunction occurs 1/4 cycle east of
the mountain crest, in approximate agreement with observations.
By use of a Fourier expansion (7.99) can be solved for realistic distributions of
topography. The results for an x-dependence of h
T
given by a smoothed version
of the earth's topography at 45˚N, a meridional wave number corresponding to a
latitudinal half-wavelength of 35˚, τ
e
=
=
17ms
−
1
, f
0
=
10
−
4
s
−
1
, and
5 days,
u
¯
=
H
8 km are shown in Fig. 7.15. Despite its simplicity, the Charney-Eliassen
model does a remarkable job of reproducing the observed 500-hPa stationary wave
pattern in Northern Hemisphere midlatitudes.
=
Fig. 7.15
f
0
/g)inthe
Charney-Eliassen model for the parameters given in the text (solid line) compared with the
observed 500-hPa height perturbations at 45˚N in January (dashed line). (Bottom) Smoothed
profile of topography at 45˚N used in the computation. (After Held, 1983.)
(Top) Longitudinal variation of the disturbance geopotential height (
≡
