As developers seek to harness energy sources in more challenging and/or deeper water environments, offshore assets are increasing in size, complexity and exposure to severe weather. Critical to the optimised engineering design, consenting and resilient operation of these developments is the characterisation (pre-construction) and monitoring (during and post-construction) of the marine environment and the prevailing metocean regimes.

Metocean data refers to the combined observation and assessment of meteorological and oceanographic data. These data, which include observations of wind, wave, flow, water level and water column properties, form critical input across all phases of an offshore energy development.

Metocean data exists within a hierarchy of quality, with two principal sources:

• Observations of phenomena; and,
• Numerical models.

Early and integrated consideration of data availability and data quality is recommended for all offshore developments. Gap analyses should inform and where possible optimise, the scope of metocean campaigns and numerical modelling efforts.

Recommendations should align with development timelines to ensure available data is sufficient in terms of data quality and coverage for each phase of the development lifecycle. This proactive approach supports schedule and budget optimisation and may lead developers to seek answers to the following questions:

• What is the value of publicly available metocean information (either historical observations or modelled data) and how can these be best utilised to support the development?
• Are metocean deployments necessary? If so, what instrumentation should be deployed, where, during which phase and for how long?
• How can numerical modelling be applied to support in characterising the prevailing regimes and extending the spatial and temporal understanding?
• Beyond metocean data, how can other data sources (i.e. geophysical, geotechnical, ecological) be integrated to support wider consenting and design workstreams?
• How is all available information exploited to fully characterise the regimes impacting the development site to assess risk to assets and potential environmental impact?

Historical or contemporary measurement campaigns offer a brief snapshot into the prevailing metocean regimes occurring above and beneath the sea surface, while numerical models enable a broader understanding of regime complexity across greater spatial and temporal scales. Metocean data acquired from observations and via numerical models is complementary: the quality and value of both datasets should be considered in a holistic manner. Observations sourced from public data records, or targeted developer-led measurement campaigns are utilised to calibrate-validate outputs of numerical models. This provides confidence that model predictions are accurate and representative of real world processes. When carefully scoped, the combination of observations and numerical modelling provides the greatest opportunity from which to develop the most comprehensive understanding of the metocean regimes interacting with offshore developments.

Due to the costs and duration (for large scale developments, multi-year campaigns are often required) involved in undertaking metocean surveys, early engagement between the developer, oceanographic survey contractor, engineers, and consultants is essential to de-risk downstream work packages and ensure campaigns are suitable to meet the requirements of the development. The duration, location(s) and approaches and systems proposed must be rigorously considered in light of cost and redundancy in both data quality and return. For example, offshore wind projects rely on floating Light Detection and Ranging (LiDAR) platforms to assess wind resource. These platforms are often equipped with additional instruments to monitor waves, tide, temperature, salinity, and water quality. Their mooring systems must withstand severe offshore conditions, maintaining data collection integrity over long durations. However, relying on a single platform type can introduce data biases, particularly at the extremes of the measurement ranges. Redundancy both in terms of data quality, as well as data return, via the simultaneous deployment of specialised monitoring buoys and seabed mounted devices alongside FLiDAR systems can enhance the quality and reliability of data acquired during measurement campaigns. In making these decisions, the development location, type, scale and risk profile (both from a consenting and engineering perspective) should be carefully considered.

Metocean Support @ Xodus
At Xodus, our global team of specialists support clients in navigating the technical, environmental, engineering and regulatory challenges of offshore developments. We offer support for all metocean project requirements including:

• Site survey planning and project management:
  - Early feasibility and data acquisition planning - ensuring a pragmatic, integrated, survey design for the development type, scale, location and engineering and consenting risk profile;
  - Supply chain support and survey contracting - supporting developers in identifying suitable contractors, scope specification, contractor screening and selection;
  - Specialist advisory support and project management in advance of, and throughout, offshore campaigns; and,
  - QA/QC of acquired data;
• Numerical modelling to increase spatial and temporal understanding of prevailing wave, hydrodynamic and sediment regimes in support of varying development requirements, including Extreme Value Analysis (EVA) and operational downtime analysis; and
• Application of metocean data in support of offshore consenting requirements, site characterisation and seafloor assessments, support through Concept, pre-FEED, FEED and Detailed Design and during the operational and decommissioning phases of a development.