194
W. Ritzrau . H. Fohrmann
er four experiments the diffusion coefficient in the BBL A/e(z) and A/d(z) was linearly proportional to the height above the seabed and the friction velocity u.
[Eq. (3)], and in this way related to the hydrodynamic regime. In experiments 2
and 3 A/cCz) was constant above the BBL, whereas in experiments 4 and 5 A/d(z)
decreases with distance above the BBL. Two different hydro dynamical regimes
represented by current velocities of ulOo of 0.1 (regime 1) and 0.5 ms- 1 (regime
2) were simulated. The first velocity of 0.1 m S-1 is a reasonable value for shelf
areas, whereas the latter describes a more vigorous regime. The results of the experiments 1-5 are summarised in Fig. 3a-f.
In all five numerical experiments the initial homogeneous concentration distributions of the three aggregate size classes with settling velocities of 30, 50 and
80 m day-l were redistributed and for all experiments steady state was reached after a simulation time of 22 h. Significant differences in concentration distributions
for all three aggregate size classes evolved between the constant Ae(z) of 0.0001
m 2 s- 1 (Fig. 3, dotted line) and the height dependent A(z) [A/e(z) dashed and A/d(z)
Aggregate size cia., 1
Se11l11lg vOlOOty 30 [m d· 1[.
Aggregale dlamelOf
o 000066 [m[
.....
.......
Hydrodynamic regime 1
U100 = [0.1 ms· 1]
Hydrodynamic regime 2
U100 = [0.5 ms-1)
Fig.3 The influence of the parameterisation of the eddy diffusion coefficient [A(z) 1 on the
vertical concentration distribution of the three studied particle sizes (settling velocities 30,
50 and 80 mday-I, respectively) was investigated in experiments 1-5 (Table l).a-c represent
simulations with u lOO = 0.1 m S-I ,d-fwith u lOO = 0.5 m day-I. The three different approaches
of the parameterisation of the eddy diffusion coefficient displayed are: 1\( z) = constant over
all model layers (dotted line); in the cases of AZc,Zd(z) = u.kz we distinguish for z > h between
Azc(z) = A(h) (dashed line) and A1d(z) = A(h) hlz (solid line) (See text for details).
W. Ritzrau . H. Fohrmann
er four experiments the diffusion coefficient in the BBL A/e(z) and A/d(z) was linearly proportional to the height above the seabed and the friction velocity u.
[Eq. (3)], and in this way related to the hydrodynamic regime. In experiments 2
and 3 A/cCz) was constant above the BBL, whereas in experiments 4 and 5 A/d(z)
decreases with distance above the BBL. Two different hydro dynamical regimes
represented by current velocities of ulOo of 0.1 (regime 1) and 0.5 ms- 1 (regime
2) were simulated. The first velocity of 0.1 m S-1 is a reasonable value for shelf
areas, whereas the latter describes a more vigorous regime. The results of the experiments 1-5 are summarised in Fig. 3a-f.
In all five numerical experiments the initial homogeneous concentration distributions of the three aggregate size classes with settling velocities of 30, 50 and
80 m day-l were redistributed and for all experiments steady state was reached after a simulation time of 22 h. Significant differences in concentration distributions
for all three aggregate size classes evolved between the constant Ae(z) of 0.0001
m 2 s- 1 (Fig. 3, dotted line) and the height dependent A(z) [A/e(z) dashed and A/d(z)
Aggregate size cia., 1
Se11l11lg vOlOOty 30 [m d· 1[.
Aggregale dlamelOf
o 000066 [m[
.....
.......
Hydrodynamic regime 1
U100 = [0.1 ms· 1]
Hydrodynamic regime 2
U100 = [0.5 ms-1)
Fig.3 The influence of the parameterisation of the eddy diffusion coefficient [A(z) 1 on the
vertical concentration distribution of the three studied particle sizes (settling velocities 30,
50 and 80 mday-I, respectively) was investigated in experiments 1-5 (Table l).a-c represent
simulations with u lOO = 0.1 m S-I ,d-fwith u lOO = 0.5 m day-I. The three different approaches
of the parameterisation of the eddy diffusion coefficient displayed are: 1\( z) = constant over
all model layers (dotted line); in the cases of AZc,Zd(z) = u.kz we distinguish for z > h between
Azc(z) = A(h) (dashed line) and A1d(z) = A(h) hlz (solid line) (See text for details).