Civil Engineering Reference
In-Depth Information
s
2
þ
2
þ
u
v
1
S M
g
ˁ
ˁ
2
A vc ¼
ð
c ML
h ML
Þ
ð
5
:
3
Þ
z
z
z
with
c ML :
¼
0.05,
h ML :
¼
thickness of mixed layer,
S M :
¼
turbulent Schmidt-Prandtl number ~1.3.
The vertical eddy diffusion coefficient A dc is described through the generally
accepted linear relation (Pohlmann 2006 ):
A vc
S M
A dc ¼
ð
5
:
4
Þ
Both parameters, the vertical eddy viscosity and diffusion coefficient, are necessary
to parameterize the Reynolds stress terms in the shallow water equations and in the
transport equation for heat (Pohlmann 2006 ). So A vc impacts the vertical exchange.
Due to that, it was possibly necessary to examine the influence of this coefficient on
the influenced ocean by keeping A vc minimal. Minimal means the usage of a laminar
A vc . That procedure helps to define its impact on the vertical velocity component and
the distribution of temperature and salinity through the vertical diffusion.
In the following, the analysis of the vertical exchange is presented, followed by
the analysis of horizontal exchanges.
Vertical Exchange
This sensitivity study aims to estimate the impact of vertical and horizontal
diffusion and advection on the new state of system after 1 day.
The analysis of the vertical exchange comprises, next to the normal run used as a
reference ( src50 ), five simulations, labeled as src60, src51, src52, src54 , and src56,
including different adjustments regarding vertical exchange. These adjustments
consider the aforementioned parameters vertical eddy viscosity coefficient A vc ,
vertical eddy diffusion coefficient A dc, and vertical advection term of temperature
and salinity (labeled here as TSVA) in their prognostic equations.
Three options regarding vertical exchange were applied:
Setting A vc to a minimum of 0.0134 cm 2 /s nearly avoids vertical exchange of
momentum. Subsequent, the momentum at surface increases, so the horizontal
velocity increases because lower layers will not be forced by momentum of
surface layer. The surface motion due to shear stress triggers the lower layers.
Setting A dc to zero avoids vertical diffusion of temperature and salinity (TS). A dc
is zero in case of a minimal A vc due to its definition. That means no vertical mass
transport of TS.
Setting TSVA to zero avoids vertical transport of temperature and salinity with
the vertical flow, thus with w -component.
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