Life in the ocean wave team
Originally established in 1854 as a service to mariners the Met Office has been helping to protect people at sea ever since. Today, the Wave Modelling team is an essential part of the Met Office’s commitment to Safety of Life At Sea (SOLAS), coastal flood forecasting, and improved weather forecasts.
Output from the Met Office Wave Modelling team is used in a variety of contexts. Many people are familiar with the shipping forecast, but the team’s work also ultimately helps efficient and safe marine operations to be carried out by operators in industries such as offshore oil and gas and renewables. Many of these services are delivered through the Met Office marine forecast centre in Aberdeen.
The Wave Modelling team develops global and regional models to forecast sea-state conditions up to seven days ahead. As Andy Saulter, Surge Waves and Met Ocean Projects Manager explains, “Models describe the evolution of ocean surface wave energy spectra, from which descriptive characteristic parameters are derived such as wave height, period, direction and whether waves are ‘wind-sea’ or ‘swell’ like. Mariners need detailed information on these parameters to make important decisions.”
As well as supplying off-shore intelligence, increasingly the team provides forecasts close to the coastline. “We have been helping the UK Coastal Flood Forecasting agencies assess coastal flood risks in tandem with tide and surge model information,” says Andy.
The team has also collaborated with the Royal National Lifeboat Institution (RNLI) and Plymouth University to develop a new Beach Safety Weather Manager tool for lifeguards (see page 21). The team has various collaborations with UK academic institutions and other national meteorological services. One key relationship is being part of the WAVEWATCH III community model developers group. “Model configurations are based on the National Centre for Environmental Prediction (NCEP) community model WAVEWATCH III, which enables us to contribute to and benefit from the efforts of a worldwide group of research and development scientists,” explains Andy.
There are two ways in which the Wave Modelling team improves accuracy of wave forecasts. “The first, more generic, activity is to pull through ongoing developments in the science community in the way that wave growth, dissipation and propagation processes are parameterised in our models,” says Andy.
“The second method focuses specifically on coastal waters,” Andy continues. “This is where we apply techniques such as grid refinement to improve how the model describes the coastline and shallow water bathymetry – improving this means we can increase the range of coastal locations for which we can forecast with confidence.”
Recent changes involved both types of improvement, along with ongoing updates to the numerical weather prediction model used to force the wave model. For example, significant upgrades to wave growth-dissipation ‘source terms’ and grid scheme were introduced to the global wave model, taking full advantage of extra computing capacity provided by our new supercomputer in order to provide forecasts out to five days ahead. The same grid scheme and physics configuration have been applied to a North Atlantic-UK ensemble wave model which provides probabilistic forecasts out to seven days ahead. All upgrades to our models are tested in parallel with operational versions in parallel suites. The latest upgrades, which were tested in parallel suite 38 (PS38), are now fully operational.
Together these updates deliver a solid improvement in the accuracy of the model. Now, forecasts of significant wave height 72 hours in advance are statistically as accurate as the 24 hours ahead forecast before PS38. Improving prediction of high energy sea-states is particularly important for maritime safety and coastal forecasts, since these events often carry the largest risks to public safety.
Latest improvements are a reason to celebrate, but the Wave Modelling team is already working on more developments. Of particular focus is further improving wave forecasts for the complex shallow and highly tidal UK waters. Simultaneously the team is testing the benefits of more direct two-way coupling between atmosphere and ocean modelling systems. Long term, representing coupled interactions could improve wave models and lead to an enhanced ability to forecast weather and climate as well.