2.0 10 1
--
-- T' = 0.212 0.013 u 2m/u
w'
*
1.6
1.2
Figure 8. Variation of covariance
w′ T′ with u2m /u* .
0.8
0.4
0
4
6
8
10
12
--
u
_ 2m
u
*
0.3
--
w' T' = 0.042 u 2m
--
0.2
0.1
0
0
1
2
3
4
5
u 2m (m / s)
_
Figure 9. Variation of covariance w′ T′ with u2m .
between u* and u2m , and a least-squares relation was developed as
u* = 0.079 u2m .
(72)
The dependence of u* on u2m is somewhat weaker when it is compared with that shown in
Figure 4 (i.e., u* = 0.113 u2m ). It can be said that over snow, ice, or partially frozen ground the
value of u* is significantly lower because there is less-intense turbulence over snow or ice than over
a grass field (~23 cm tall).
Figures 11 shows the relation of σw′ and σ u′ with u2m . The linear least-squares correlation can
be expressed as
σ′ = 0.113 u2m
(73)
w
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