Simple Coastal Wave Modelling
From Ocean Wave Climate
Satellite data together with long-erm offshore WorldWaves model data is used to estimate coastal wave energy resources.
During autumn 2009, Fugro OCEANOR started to use satellite data together with long-term offshore WorldWaves model data to estimate the coastal wave energy resources. The methodology was described and validated in a paper presented by us at the 8th European wave and tidal energy conference in Uppsala, Sweden (Barstow, S.F. et al. WorldWaves wave energy resource assessments from the deep ocean to the coast). A simple summary of the methodology is given here.
The WorldWaves offshore database we have accurate offshore model time series of wave heights, periods and directions which are calibrated against offshore satellite data ensuring unbiased wave data. The satellite data (see World Wave Atlas) are available along fixed ground tracks. Each time a satellite passes from offshore to nearshore it measures a practically instantaneous profile of the significant wave height with an along-track resolution of about 6km. Thus, for a Topex track we have profiles of significant wave height from deep offshore waters to the coast about every 10 days over a 10-year period. This information can then be used to adjust the offshore grid point data to various points along the satellite tracks and give reasonably accurate wave height statistics closer to the coast, although the data will be a spatial average over the altimeter footprint.
This methodology was first used for a leading European power utility to provide additional resource data along the Norwegian coast and in the North Sea. In the paper linked to above, we validate this methodology successfully against US coastal wave buoys on the west coast. The method is obviously limited to the satellite ground tracks and to about 6 km resolution along those tracks, but it does give high quality estimates of the wave energy resource for a much more reasonable price than the much more expensive modelling option. Therefore, this can be useful for those requiring a quick look at the resource nearer to the coast. An example is given below of the end result for wave energy resources off Norway.
Highlighted satellite track. This satellite flew towards the south east. The along-track mean significant wave height is shown below.
Mean along-track significant wave height for the portion of the track in the figure above to the north of Ireland. The rapid decrease of wave height in towards the coast is seen. The distance between each “point” is about 6km (please note that the point data represents a spatial average around each point and are not therefore site-specific). This information can be used as a simple wave model enabling us to estimate long-term wave statistics closer to the coast.
The map shows the additional locations (yellow dots) at which seasonal wave energy resource estimates can be made in coastal waters along the Norwegian west coast combining the satellite altimeter data and offshore model data.
Using the satellite data we can construct seasonal wave power plots giving a quick and relatively cheap overview of the wave energy resources nearer the coast. This figure shows the September to November wave energy resource estimates along the Norwegian coast.