Tidal Stream Models
Tidal Stream Models
What is a tidal model?
Hydrodynamic models seek to replicate nature. They are essentially a set of equations that calculate how water moves from one place to another by taking into account all the forces that generate tides. They have been around for 30-40 yrs, but until now have been the preserve of Government agencies, oil companies and specialist environmental modelling companies. Until fairly recently they could only be run on Supercomputers. These days we can develop and run high resolution models on a fast laptop.
Tides are inherently predictable, so unlike a weather model, a tidal model can be relied upon months or even years into the future provided the bathymetry (depths) don't change significantly. When combined with a short term forecast of atmospheric pressure, wind and rainfall/ river discharge, a "tidal forecast" can be produced which will increase the accuracy of the model output. Tidal models that take into account weather and rainfall/ river flow are known as 'operational models'. They can be used to forecast storm surges and other damaging events.
Developing a tidal model requires a high degree of mathematical ability, an extensive background in oceanography and highly specialist expertise in the particular science of marine modelling. Our science team, Dr Roger Proctor and Dr Roger Flather both worked as research scientists for most of their careers at the UK National Oceanography Centre NOC (formerly the Proudman Oceanographic Laboratory ) which is regarded as the world's leading centre for tidal research.
As part of their work at NOC Dr Proctor and Dr Flather worked on many prestigious projects including the UK's Southern North Sea model which informs decisions when to lower or raise the Thames Barrier.
How do you construct a model?
To develop a model we need 3 main things.
- Detailed bathymetry which we then divide into a grid e.g. lat, long, depth
- Accurate boundary condition (what the sea level and current is doing outside the model domain (area))
- A set of equations that calculate how the water moves from one grid box to another.
3D bathymetric schematic of St Catherine's Point - Isle of Wight
The more accurate and detailed the bathymetry and the smaller the grid box, the more accurately the model can describe nature. This is normally only an issue at complex features, such in estuaries and at their mouth.
100m grid box is ok for Solent and more than enough for IOW. We may look in the future at doing 50m grid for central Solent to better resolve Cowes Roads, Gurnard etc
Grid point spacing over Bramble Bank - depths are in m
