Marine observations: Underpinning forecasts and climate understanding 

These observations are essential for accurate weather forecasts, warnings for those at sea, and for monitoring and deepening our understanding of the global climate system. The oceans cover more than 70% of the Earth’s surface, and the state of the atmosphere is closely linked to changes in the oceans themselves.  

This article explores how marine observations are taken, the technology and platforms involved, and the many ways in which this data is used. 

Why marine observations matter 

Observations over the oceans are crucial for several reasons: 

• Safety at sea: They provide forecasts and warnings to help ships and offshore operators avoid severe weather. 

• Weather & marine prediction: They feed into computer models that predict the future state of the atmosphere and the ocean. 

• Climate research: They supply long-term information, helping scientists track and understand changes in the global climate. 

Atmospheric changes over months, decades, and centuries are often driven by the state of the oceans. To understand these changes, observations are needed not just at the surface, but also below it, to inform ocean circulation models and provide initial conditions for ocean modelling. 

READ MORE: The UK land observation network: Underpinning weather and climate understanding 

How marine observations are collected 

The Met Office gathers in-situ marine observations from five main sources: 

• Moored platform Network: Observations collected from autonomous marine observing systems placed on moored buoys and light vessels. 

• Voluntary Observing Ships: These include both manual observations reported by ships crew and also automatic observations collected from autonomous marine Observing systems placed on ships. This gives us weather data from a wide range of locations as ships cross the world's oceans. 

• Third party data: Observations received from automatic weather stations installed at offshore installations. 

• Drifting buoys: Small, battery-powered buoys that drift with ocean currents. 

• Argo floats: Compact robotic instruments that drift with the deep ocean currents and descend to the depths of the oceans, collecting data profiles from the abyss to the surface. 

• Gliders: Measuring from near the seabed to the surface, gliders are similar to Argo floats and are often deployed in shallower shelf seas. Their trajectories can be modified when they resurface. 

These observations are not limited to UK waters. The Met Office contributes to an international effort, the Global Ocean Observing System (GOOS), co-sponsored by the World Meteorological Organization (WMO), the Intergovernmental Oceanographic Commission of the United Nations Educational, Scientific and Cultural Organization (IOC-UNESCO), the United Nations Environment Programme (UN Environment), and the International Science Council (ISC).  

The Met Office also works with regional bodies such as EUMETNET and EuroArgo, as well as its partners in the UK. This ensures a global network of marine data, supporting both national and international needs. In-situ observations also play a crucial role in calibrating ocean observations made from space using satellites. 

Marine Moored Platform Network 

The Met Office operates a network of marine automatic weather stations, including moored buoys sat in an arc to the west from Brittany in Biscay to the North of Scotland. Also included in the network are 4 systems on lightships, 1 buoy in the channel and two off the coast of Plymouth.  

Each moored buoy stands 7 metres tall, measures 3.6 metres in diameter, and weighs 4.5 tonnes. They are anchored in deep ocean locations with cables several kilometres long. Deployment requires a ship with heavy lifting gear, and each buoy can operate for up to two years between service visits. 

Moored buoys measure: 

• Air pressure 

• Air temperature 

• Sea temperature 

• Humidity 

• Wind speed and direction 

• Wave height and period 

• Directional wave parameters

Designed for the harsh conditions of the north-eastern Atlantic, these buoys are solar powered but can run for around three to six months on batteries alone. All critical components are duplicated to provide backup in case of system failures, ensuring resilience and reliability. 

READ MORE: Seeing the bigger picture: How satellite data shapes Met Office forecasts 

The development of the moored buoy network was accelerated due to the Great Storm of 1987. It was hoped that placing buoys to the waters to the west of the UK  would give weather information and early warning of harsh/dangerous weather. Back in 2013, the network recorded wave heights of 19 metres, while during the winter of 2007/8, the network recorded wave heights of 18.2 metres and 17.6 metres. These events are  among the highest ever recorded by the network. Such data is vital for monitoring trends in severe wave conditions, which appear to be increasing in the north-east Atlantic. 

The data is used to: 

• Produce forecasts 

• Monitor developing weather conditions 

• Provide information on the climatology of oceanic and coastal areas 

• Validate satellite observations 

• Validate and develop forecasting models 

Lightships  

Lightships are permanently moored vessels with light beacons to aid navigation. They provide a stable platform for marine automatic weather stations, measuring the same parameters as moored buoys, with the addition of visibility. 

Observations from ships 

Ships and offshore oil platforms are invaluable for collecting meteorological data in otherwise data-sparse ocean regions. The Met Office maintains observing capabilities on 210 voluntary observing ships (VOS) operating worldwide. Officers and crew on these ships are encouraged to record and transmit weather observations, supporting the WMO’s World Weather Watch and the WMO Voluntary Observing Ship Scheme. 

Observations from ships are typically made every three to six hours while at sea and transmitted back to the Met Office by satellite. About half of the UK’s ship observations come from European waters and the North Atlantic, with the remainder from further afield. 

READ MORE: How the Met Office uses radar to deliver accurate weather observations and forecasts 

Manual Voluntary Observing Ships 

The UK manual VOS fleet consists of over 150 vessels. Extensive metadata are collected for these vessels to ensure a higher-quality data for climate applications. The data is monitored to ensure it meets a minimum quality standard before sharing internationally for climate research purposes. In addition to its role observations provider, The Met Office also acts as one of two Global Data Assembly Centres (GDAC’s) for marine climatological data, responsible for quality control and dissemination of ship observations data from other National Met Services VOS fleets.

Shipborne automatic weather stations (AWS) 

Automation on UK observing ships has increased significantly, with automatic weather stations now installed on ferries, container ships, and research vessels. These systems can automatically measure and transmit basic meteorological quantities at hourly intervals, improving the frequency and reliability of data. 

The Met Office has developed its own AWS system, known as AMOS (Autonomous Marine Observing System), which measures pressure, temperature, and humidity, with the capacity to add more parameters. AMOS  transmits data via a built-in Iridium transmitter, allowing for two-way communication and easy installation. 

Drifting buoys and Argo floats 

The global array of around 1,250 drifting buoys provides essential data for both forecasting and climate studies. Drifting buoys are a primary source of air pressure data over the oceans, which is critical for weather forecasting models. They also measure sea temperature, and salinity, vital for understanding the global climate. 

Drifting buoys are battery powered, typically lasting one to two years. They usually measure sea temperature and air pressure, and by tracking their positions, surface currents can also be determined. Some buoys are equipped with sensors for wind and salinity. Data is transmitted to satellites, primarily using the Argos system, though new systems such as Iridium are being evaluated. 

The Met Office deploys 20 to 30 drifting buoys each year in the North Atlantic, coordinating with European partners, and also contributes to the GOOS Global Drifter Array by deploying buoys in the South Atlantic and Southern Ocean. 

Argo floats are compact robotic instruments that drift with the deep ocean currents and descend to the depths of the oceans, collecting data profiles from 2,000m to the surface . The UK contributes around 25-30 floats per year to the global Argo array, which presently comprises around 4,150 floats. Recent technological developments have widened the scope of the Argo array to also operate in seasonally ice-covered regions, measure biogeochemical parameters (over 840 floats have one of more biogeochemical sensor), and to measure from 6,000 m deep to the sea surface (around 200 floats).

The resulting observations are crucial for understanding ocean circulation, heat content, sea level changes and biogeochemical processes including the carbon cycle. Argo data provides initial conditions for short-range and seasonal ocean forecasting, coupled ocean-atmosphere weather forecasting, as well as climate modelling.

Marine gliders

Marine gliders are the latest recording equippment to send data to the Met Office. They are autonomous underwater vehicles that operate for extended periods, often up to six months, surveying ocean depths of around 200 metres. Similar to Argo floats but typically used in shallower shelf seas, gliders collect vital oceanographic data such as temperature and salinity from near the seabed to the surface.

Their trajectories can be adjusted remotely when they resurface, allowing for flexible and targeted observations. The data they gather is transmitted in near real-time to organisations like the Met Office, where it supports improved weather and ocean forecasting. This enhanced observational input feeds into advanced computing systems, helping to refine forecast accuracy for maritime operations and broader climate monitoring.

How marine data is used 

The data collected from these various platforms is used in multiple ways: 

• Forecasting: Real-time data from buoys, ships, and floats feeds directly into weather models, improving the accuracy of forecasts and warnings for mariners and coastal communities. 

• Climate monitoring: Long-term records help scientists track changes in oceanic and atmospheric conditions, contributing to our understanding of climate variability and change. 

• Research and development: Marine observations support research into ocean circulation, wave dynamics, and the interactions between the ocean and atmosphere. 

• Satellite validation: In situ measurements provide ground-truth data for calibrating and validating satellite observations. 

• Model validation and developments: Forecasts and projections rely on models of the Earth system, their continuous development is guided by these observations. 

Marine observations are a vital part of the Met Office’s mission to provide accurate forecasts, warnings, and climate insights. Through a combination of advanced technology, international collaboration, and dedicated platforms, the Met Office ensures that high-quality data from the world’s oceans continues to underpin our understanding of weather and climate. 

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