Environmental Engineering Reference
In-Depth Information
spawning dates. The runs were purely deterministic but the effect of day-to-day
flowfield variability results in differences in the trajectories of particles released
from the same location on different dates (Fig.
20.2d
, compared to 20.2a). Indeed,
the effect of particle release pattern on particle trajectories is similar to that of
horizontal diffusion (see Fig.
20.2b-c
), although the effect on the distribution of
juveniles is more spatially variable than that of horizontal diffusion (compare
Fig.
20.3d
with 20.3c but note the different colour scales). The MAE of this simula-
tion compared with the baseline is 0.0539.
20.3.4 Vertical Behaviour
The particle tracks of simulations with particle vertical migration behaviour
(Fig.
20.2e
; run with DVM pattern not shown) were quite similar among them-
selves and to those of the baseline run, where all particles were kept at a constant
depth (Fig.
20.2a
). However, there are some absolute differences between the
end distribution of juveniles at the end of these runs (Fig.
20.3e
; run with DVM
pattern not shown) compared to the baseline (Fig.
20.3a
). The DVM pattern has
larger absolute differences than the “ontogenetic” one but the latter is more
geographically variable. Their MAE values were 0.0763 and 0.0823, respectively.
20.3.5 Settlement Rules
The effect of additional settlement rules on the trajectory of the particles was very
small (compare Fig.
20.2f
with 20.2a). This was expected since the consequence of
the additional constraints is just to prolong the pelagic stage of any juveniles ready
to settle (where there is either no spare demersal carrying capacity or suitable depth)
until suitable conditions are found. The only appreciable differences between the
baseline (Fig.
20.3a
) and the present runs are in some limited areas in the west coast
of Scotland and central northern North Sea (Fig.
20.3f
). The MAE was 0.0344.
20.3.6 Combined Factors
Since both horizontal diffusion and extended particle release patterns had the effect
of “spreading out” the particle trajectories, it is not surprising that those were quite
similar among the two runs with multiple changes to the characteristics of the
baseline run (the two bottom lines on Table
20.1
). However, horizontal diffusion
had a greater effect on the spread of the final distribution of settlers than a Gaussian
particle release pattern, as demonstrated by a greater MAE (0.1039 and 0.0908,
respectively).
