What is metocean data, and why do projects in the Gulf of Guinea need it?
Geomarins Integrated Limited ·
A plain-language guide to metocean data: what is measured, how it is used in design and operations, and why site data matters off Nigeria and West Africa.
Metocean is short for meteorology and oceanography. Metocean data describes the physical conditions at sea and along the coast: wind, waves, currents, water levels, air and water temperature, pressure and visibility. Anything built in or near the sea, and any work done on the water, depends on knowing these conditions.
What is measured
- Waves: height, period and direction of both locally generated sea and long-distance swell
- Wind: average speed, gusts and direction at a known height
- Currents: speed and direction, often at many depths through the water column
- Water level: tides, storm surge and long-term changes
- Weather: air pressure, temperature, humidity, rainfall and visibility
- Water properties: sea temperature and salinity
How the data is used
Engineers use metocean data to design platforms, jetties, breakwaters, pipelines, moorings and coastal defences. They need to know both the everyday conditions a structure will see through its life and the extreme conditions it must survive, such as the 100-year storm.
Operations teams use it to plan and run marine work. A supply vessel transfer, an offshore lift or a pipe lay each has limits on wind, waves and current. Knowing how often those limits are exceeded in each month lets planners choose the right season and the right vessels, and live data tells them whether it is safe to work today.
Environmental teams use metocean data to understand how pollutants and sediments move, and to forecast the path of an oil spill.
Why the Gulf of Guinea is different
The sea off Nigeria is often described as benign compared with the North Sea or the Gulf of Mexico, and there are no hurricanes. But it has its own challenges. Long-period swell generated by storms far to the south in the South Atlantic arrives almost all year round, and long-period swell can make vessels and floating structures move more than its modest height suggests. Squall lines moving off the land can bring sudden strong winds with little warning. Near river mouths and in the Niger Delta, currents and water levels change with river flow and tides.
Global models and datasets give a useful first picture, but they do not capture every local effect. That is why projects measure at their own site, using buoys, current meters and weather stations, and use the measurements to check and improve model data.
Measured versus modelled data
Most metocean studies use both. Measured data from instruments at the site is the most accurate description of conditions there, but records are usually only months or a few years long. Model hindcasts reconstruct conditions over decades, giving the long records needed for extreme values, but they carry model errors. The best results come from using measurements to check and calibrate the model.
Getting started
If you are planning a project at sea or on the coast, the first step is to decide what questions the data must answer and how long a record you need. From there, a measurement campaign can be designed: instruments, location, duration and how the data will reach you.