Winter 2005

Liverpool Bay Coastal Observatory:

towards a UK real-time coastal prediction system

Phil Knight

Proundman Oceanographic Laboratory

The Proudman Oceanographic Laboratory, on the University of Liverpool precinct, is involved in several research projects from the Antarctic to the Arctic Ocean. The Coastal Observatory project is closer to home, based within Liverpool Bay and the Irish Sea.

We aim to understand more about how coastal seas respond to natural forcing and the effects of human activities. Our interest is in the seasonality, impacts of storms, variations in river discharge (especially the Dee, Mersey and Ribble) and plankton blooms. We are making a large number of measurements, and developing state-of-the-art ocean forecasting computer models.

By building up long term records of oceanographic and atmospheric observations in Liverpool Bay, we can study the whole ecosystem, as well as interactions between the sea and the coast. A result of measuring nutrient levels for example (to check if they exceed European Union guidelines) will indicate whether action is required to reduce their input from local rivers.

Plan of near shore monitoring methods. These measurements help us to critically test our forecast models, in the same way that the Met Office use collected data to produce better weather forecasts. Furthermore we are developing higher resolution models to predict more detailed localised effects. Eventually, these models will be run at the Met Office for the whole of the UK’s coastal seas, providing management tools for local and national Government.

The Coastal Observatory web site ( delivers data and information to researchers and the public. Most data are freely available, some in real-time, e.g., weather observed at Hilbre Island, and near-surface measurements from the Liverpool to Belfast ferry. Our main partners are the Met Office, Environment Agency, Department for Environment, Food and Rural Affairs (Defra) and Centre for Environment, Fisheries and Aquaculture Science (CEFAS), with contributions from the University of Liverpool, University of Wales Bangor, National Oceanography Centre Southampton and Plymouth Marine Laboratory.

What measurements are we making?

Our measurements within Liverpool Bay and the Irish Sea are:

  • The main mooring site near to the Mersey Bar light vessel (installed in August 2002), provides current profiles, and sea-bed and near-surface temperature and salinity records. A second site (installed in April 2005) close to the North Hoyle wind farm also includes turbidity and chlorophyll. At present, data are stored and then retrieved during maintenance cruises. Development of underwater acoustic data transmission is in progress so that these sub-surface measurements can be sent in real-time.
  • A CEFAS SmartBuoy (, installed in November 2002, records surface properties including salinity, temperature, turbidity, nutrients and chlorophyll, and transmits data in real-time.
  • A WaveNet directional wavebuoy, also installed in November 2002, sends spectral wave components in real-time (
  • Moorings are serviced approximately every six weeks (four weeks in summer to reduce biofouling of sensors) on the RV Prince Madog. Spatial CTD and nutrient surveys of Liverpool Bay are carried out during each cruise.
  • The Liverpool – Belfast/Dublin ferry, Liverpool Viking, has sensors for recording near surface temperature, salinity, turbidity and chlorophyll. We will soon add a nutrient analyser. This is one of nine ferry routes under study in a European Union research project (

    Sea surface temperature as recorded by ferry and predicted by model for 2004

  • Most tide gauges in the UK Tide Gauge Network send real-time data. Tide gauges in the Irish Sea, where appropriate, form part of the Observatory.
  • A weather station on Hilbre Island provides real-time information (atmospheric pressure, wind speed and direction, cloud cover, rainfall). There is also a web camera.
  • NERC’s Remote Sensing Data Acquisition Service produces weekly composite satellite images - infra-red (for sea surface temperature) and visible (for chlorophyll and suspended sediment) radiation.
  • River flow data collected by the Environment Agency, are sent to us daily. The data are input into our hydrodynamic forecast models to improve predictions in near-shore areas.
  • Recently, the Observatory has added two different radars : a HF radar (12 MHz) with 80km range records surface currents in 2x2km bins in 20 minute intervals and surface waves in 5x5km bins every hour; a X-band radar (9 GHz) with a 2km range records surface waves at 84 second intervals.

    What are models and what do they do?

    Our hydrodynamic models forecast parameters representing physical conditions in the sea, such as tidal elevations and currents, sea temperature and salinity. We can extend our modelling system to predict sediments, chemistry and biology, as well as nest smaller scale models within larger scale models. In Liverpool Bay we are running a model with 200m resolution: more detailed features can be resolved, like eddies at the mouth of the Dee Estuary.

    POLCOMS (Proudman Oceanographic Laboratory Coastal Ocean Modelling System, polcoms) is a 3D modelling system consisting of a hydrodynamic model linked to a surface wave model, a sediment transport model and an ecosystem model. We are collaborating with the UK Met Office to run these nested models covering the northwest European ocean/shelf (12km resolution), the Irish Sea (1.8km) and focusing on Liverpool Bay (100-300m resolution).

    Outputs from different models runningat different spatial scales

    Models are driven by meteorology from a Met Office forecast model, and with ocean forcing from the North Atlantic 35km grid model. These have been operational since December 2002 and provide the boundary conditions for the Irish Sea model, which in turn provides boundary conditions for the Liverpool Bay model. Real-time local river discharges from the Environment Agency are also included.

    The 3D baroclinic models for the Irish Sea and Liverpool Bay include wavecurrent interaction, and performance is checked against in-situ measurements of temperature, salinity, current and waves and coastal sea-level. Data assimilation techniques enhance the value of the data and improve the accuracy of the model forecasts.

    Recently, nutrients and plankton dynamics have been simulated by a coupled ecosystem model and sediment transport module. These show that suspended sediments are important for controlling biological processes in the shallow eastern Irish Sea, by affecting available light levels. The results have been validated against data from the SmartBuoy, the instrumented ferry and ocean colour information from satellites.

    What information is available online?

    The collected data, and especially realtime data, are available both numerically and as graphics via a dedicated website Forecasts, up to 48 hours ahead for most variables are displayed and compared with measurements where possible, for example, daily mean sea surface and sea bed temperatures, currents, waves and sea surface heights.

    The web site is tailored for scientists, coastal zone managers and the general public. Data are freely available after registration, although most graphical information can be viewed without the need to register.

    Researchers and other interested groups are welcome to join the Coastal Observatory, to take advantage of the existing monitoring programme, and to do their own process studies. For more information visit the website or contact Phil Knight e-mail: )

    Contact details:
    Proudman Oceanographic Laboratory
    6 Brownlow Street
    L3 5DA