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In-Depth Information
30 times greater than in the IOBL, the corresponding dimensionless height at
the standard 10-m sampling level in the atmosphere would be
03,
i.e.,fromanatmosphericsurfacelayerperspective,thesurfacelayerunderthefreez-
ingleadremainsclose toneutralstability.
Duringthelead3 deployment,we usedamastwith fourTICsspanning6m that
couldbeloweredasaunitin theupperocean.Duringmostofthe time
ζ
=
z
/
L
−
0
.
the
mastwaspositionedwithintheupper10mofthewatercolumn,butwasloweredto
about midway in the mixed layer (14-20m) for the last 3h with sufficient relative
currentforacceptableturbulencemeasurements(McPheeandStanton1996).
By again considering peaks in the area-preserving
w
spectra, we calculated av-
erage
(
∼
12h
)
λ
peak
values for the various measurement levels (Fig. 5.14). The significant
featurewas thatthe scales inferredfromthe spectralpeakswere almostan orderof
magnitude greater than would be expected had the IOBL been neutrally stratified,
i.e.,
4m. The curves plotted in Fig. 5.14 represent the mixing
lengthsassociated with the unstabledimensionlessshear formulationsdiscussed in
Section4.1.3.Theverticaldashedline,whichcloselymatches
λ
N
=
Λ
∗
u
∗
0
/
f
1
.
λ
peak
at9.4mdepth,
is
d
ml
, i.e., von K´arm´an's constant times the depth of the well mixed layer, 28m
duringlead3.
κ
λ
Mixing length,
0
λ
=
κ
|z|(1−
ζ
)
2
−5
−10
)
1/4
=
|z|(1−15
λ
κ
ζ
−15
−20
λ
=
κ
|z
ml
|
−25
0
5
10
15
m
Fig. 5.14
Averagemixinglengthfromspectral peakswhenthemastwasshallow(square symbols)
and mid-depth in the well mixed layer (circles). A limit based on
times the depth of the well
mixedlayer isindicatedbythedashed vertical line(Adapted from McPhee 1994. Withpermission
American Meteorological Society)
κ
