Geoscience Reference
In-Depth Information
Figure 10.1 A sketch of profiles of kinematic shear stress (left) and mean wind
(right) in the near-neutral ABL for
z
-independent
U
g
and
V
g
.
Figure 10.2 A sketch of velocity spectra in the convective surface layer.
surface,
z
, has traditionally been used as the turbulence length scale in the surface
layer. But particularly in the unstable case the largest, ABL-filling eddies cause the
horizontal wavenumber spectra of
u
and
v
near the surface to peak at wavenumbers
of the order of the inverse of the ABL depth
h
. These large-scale horizontal motions
near the surface have been termed
inactive
(
Bradshaw
,
1967
).
The streamwise mean momentum
equation (10.1)
near the surface scales as
u
2
∂uw
∂z
h
∼
=−
fV
g
.
(10.3)
This is small when nondimensionalized with surface-layer scales:
z
u
2
∂uw
∂z
∼
z
h
1
.
(10.4)
∗
