729 
equations - i.e. the strait was considered as a chan 
nel where the velocity in each cross section just de 
pends on the depth (Svensson 1978). The representa 
tion of Öresund in the computational model is shown 
in Fig. 12. A longitudinal section is also shown in 
the same figure with inflow boundary at Malmö and 
outflow boundary north of Helsingör-Helsingborg. The 
tunnel is the shaded part. A calculated pycnocline is 
clearly visible. 
The approximations of the flow inherent in the 
"channel" approach could be compared to satellite 
data. One could point at two discrepancies: 
- according to Figs. 7, 8 the flow seems rather 
curving with significant accelerations perpendicular 
to the channel axis 
the flow is not homogeneous in a cross section 
- within the strait and at the southern boundary, 
Figs. 7, 11. 
Another study concerned the effect of landfillings 
at Landskrona on the flow pattern from navigational, 
erosional and water quality point of views (Larsen 
1975). The 2-D shallow water equations were used and 
boundary values for a small computational water area 
were partly obtained by computing the flow in the 
whole Öresund. Fig. 13 shows the present conditions 
with a small island. The continuous line shows the 
boundary for computations. Fig. 13 also shows the 
computed flow pattern for overall current to the 
north in the strait and for the present geometry. It 
is evident that correct boundary values of the flow 
are of utmost importance for predicting the flow 
within such a small area, especially when the boun 
dary is cutting across an eddy, Fig. 8. 
These two applications indicate the usefulness of 
satellite flow information in the context of numeri 
cal modelling: 
choosing an appropriate form of approximation of 
the hydrodynamic equations (1-D, 2-D vertically or 
horizontally) 
discerning important flow mechanisms that should 
be modelled (Coriolis effect) 
choosing suitable boundaries for detailed flow 
computations (avoiding eddies on the boundary) 
obtaining flow characteristics on the model boun 
daries (inflow to the southern part of Öresund) 
calibration and validation (use of detected 
streamlines) 
determining density and distribution of grid 
points (i.e. a dense net close to Barsebäck where the 
flow seems complex). 
5. CONCLUSION 
Satellite imaging has demonstrated its potential of 
providing flow information in Ôresund. The findings 
have implications in several respects as to numerical 
flow modelling. 
In order to fully exploit the possibilities of re 
mote sensing in coastal water studies the imaging 
must have good spatial and temporal resolutions in 
suitable wave length bands (especially the far infra 
red). However, there is no satellite today combining 
these properties. Furthermore, atmospheric conditions 
often prohibit satellite based remote sensing in 
Sweden. 
Thus methods which are more independent of weather 
conditions will be of interest in the future when 
studying dynamic processes such as water circulation. 
One such method is based on active micro-wave tech 
niques in combination with Synthetic Aperture Radar. 
The mechanisms involved in imaging the water surface 
are, however, far from fully understood. 
REFERENCES 
Harremoës et al 1966. Report on the investigations of 
the Swede-Danish Committee on Pollution of the 
Sound 1959-64. 
Jönsson, L. 1984. Remotely sensed surface temperatures 
and suspended material as sources of information 
on water circulation - a study on coastal waters 
in Kattegatt and Scania. Dept of Water Resources 
Engineering, University of Lund, Sweden. 
Larsen, P. & Wittmiss, J. 1975. Landskrona-influence 
of proposed landfillings and dredgings. Hydro-ttech- 
nical investigation. Dept of Water Resources Engi 
neering, University of Lund, Sweden. 
Svensson, J. & Wilmot, W. 1978. A numerical model of 
the circulation in Öresund. Evaluation of the effect 
of a tunnel between Helsingör and Helsingborg, SMHI, 
Sweden, Nr RHO 15.