Surge Tide Modelling

Seamode Oceanographic offer the following services internationally:

  • 2D models, giving elevation and depth average flows.
  • Large area and local tide models: tidal elevation, tidal currents.
  • Large area and local tide-surge models.
  • Tidal prediction based on model results.
  • Hindcasts of tide/surge elevations.

We can provide tide surge models with good approximations to the astromical and surge tides in your area. These provide excellent geographical coverage, with a resolution of up to 200m available for a high resolution model. If you're looking for a smaller geographical area, with even higher accuracy, we would instead recommend gauge data (where model predictions with accuracy better than 10cm are possible at present).

Surge models are forced by tidal and wind data. We can also use the hindcast wind stress data from the ECMWF or NCEP reanalysis to represent historical surges. We can produce surge elevations at the model resolution for long periods and these can then be used to produce surge and extreme level statistics for a given location. It is also possible to use met forecasts to give surge predictions.

Example: Large scale surge tide model

We produced a model of the UK and Irish coasts which calculates values of the astronomical and surge tide at a resolution of about 3km along the coasts. We validated this model using tide gauge results, making it possible to calculate surge statistics (e.g. return periods, tide surge interactions, etc) for each of these points. In addition, it is possible to model individual surges to see how the response varies with position.

The model is driven with the Met Office ERA40 reanalysis data , which enables the calculation of the period 1957-2002, but can also use other met forcing, e.g. NCEP re analysis or regional models. The figure below shows surge residuals from the model for early 2002 compared with gauge data at the sites of the class A tide gauges around the UK coast, taken from data supplied by the NTSLF. The rms errors in cm are shown next to the station names. The model output has a spacing of about 3km, compared with typically 40km for the gauge data. The graph below shows only a few of the cities covered, you may also wish to see the complete model.

Large scale surge tide model

Example: High resolution surge models

For areas where the resolution of the large scale model is insufficient, Seamode Oceanographic Services can use the results of the large scale model to drive a higher resolution model. In this way, we have achieved coastal resolutions of as little as 200m. These models calculate surge and astronomical tides and can used in the same way as large scale models to calculate surge statistics on a more local level. The higher resolution is particularly important in wide areas of shallow water, where local effects can be important.

Here an example of surge elevations for the North West coast of England is shown (click diagram for a close-up).

High resolution oceanography models

Shelf wide models

Seamode Oceanographic have extensive experience in modelling surge tides in deep and shallow water in the NE Atlantic. The Princeton Ocean Model has been used in 2d model to provide a fast, PC based simulation of tide and surge elevations over the shelf and deep ocean to the NW of Europe. This model is driven by a global tidal model and ECMWF or NCEP reanalysis meteorological data. Typical resolution at the coast is 3-5km. Model performance is optimised using feedback between the coastal tides and the boundary tides and bathymetry.

model domain

 Example of model domain

Local Models

Here, elevation and flow data from the large scale model is applied using innovative assimilation and correction techniques to drive small scale local models. Tidal and surge elevations accurate to better than 10cm are feasible using this technique.
Again, long term simualtions are possible, to retrieve surge statistics for a given area; alternatively surge forecasting systems can be produced.

prediction of surge residuals, Workington, 2002

Prediction of surge residuals, Workington, 2002

For more information please contact:

Peter Bowyer, Oceanographer
services@seamodeoceanographic.com

International tel: +353 86 8216381
Tel. from Ireland: 086 821 6381