Geoscience Reference
In-Depth Information
Figure 9.9 Contours of potential temperature measured at two time periods in an
ABL over slightly irregular terrain. Upper: before the morning surface heating
began. The contours tend to follow the terrain, but with distortion. The lowest
surface temperatures are slightly upstream of the valley centers, but the upstream
slopes are generally warmer than the downstream slopes. Lower: Two hours later,
when the mixing process driven by the surface heating is essentially complete.
Turbulent mixing has nearly obliterated the horizontal and vertical temperature
gradients that had been established during the night and the surface is now about
5 K warmer than the mixed layer. From
Lenschow
et al
.
(
1979
).
and
U
i
. The horizontal components of the mean momentum
equation
(8.65)
thus reduce to
=[
U (z), V (z),
0
]
∂U
∂t
+
∂uw
∂z
1
ρ
0
∂P
∂x
+
=−
2
3
V,
(9.17)
∂V
∂t
+
∂vw
∂z
1
ρ
0
∂P
∂y
−
=−
2
3
U.
