Observing Sea States

Sea state information is needed for many applications, ranging from safety at sea and on the coast, for which real time data are essential, to planning and design needs for infrastructure that require long time series. The definition of the wave climate and its possible evolution requires high resolution data, and knowledge on possible drift in the observing system. Sea state is also an important climate variable that enters in air-sea fluxes parameterizations. Finally, sea state patterns can reveal the intensity of storms and associated climate patterns at large scales, and the intensity of currents at small scales. A synthesis of user requirements leads to requests for spatial resolution at kilometer scales, and estimations of trends of a few centimeters per decade. Such requirements cannot be met by observations alone in the foreseeable future, and numerical wave models can be combined with in situ and remote sensing data to achieve the required resolution. As today's models are far from perfect, observations are critical in providing forcing data, namely winds, currents and ice, and validation data, in particular for frequency and direction information, and extreme wave heights. In situ and satellite observations are particularly critical for the correction and calibration of significant wave heights to ensure the stability of model time series. A number of developments are underway for extending the capabilities of satellites and in situ observing systems. These include the generalization of directional measurements, an easier exchange of moored buoy data, the measurement of waves on drifting buoys, the evolution of satellite altimeter technology, and the measurement of directional wave spectra from satellite radar instruments. For each of these observing systems, the stability of the data is a very important issue. The combination of the different data sources, including numerical models, can help better fulfill the needs of users

Wave measurements, needs and developments the next decade

A recent workshop on in-situ wave measurement technology noted that: (1) geographical coverage of insitu data is still very limited especially as far as any measure of wave directionality is concerned, and most measurements are taken near coasts in the Northern Hemisphere; (2) present in-situ reports are not standardized resulting in impaired utility; (3) significant differences exist in measured waves from different platforms, sensors, processing and moorings. Three main topics were discussed: (1) how to add wave observing capabilities to drifting buoys; (2) how to assess and improve the quality of observations from the present networks of moored buoys; 3) the addition of wave observation capabilities to future moored buoy networks

Surface In situ Datasets for Marine Climatological Applications

Climatological products are required for monitoring and studying global climate change and accurately identifying secular trends over the past two centuries. These products require consistent and well-characterised observational data and metadata from the earliest ship observations and from the modern ocean observing system. Maintaining and developing long-term surface marine climatological datasets requires a different approach to data management than for operational applications. The current management of climatological datasets is discussed and specific modernization steps recommended. The status of relevant in situ observing systems is reviewed in the context of available satellite data. The extent to which requirements for maintaining sampling, redundancy, and consistency are met by existing data delivery mechanisms is considered. Recommendations include: data and metadata rescue; maintaining consistency with the historical record; modernization of data flow and climatological products; for observations with added-value through improved metadata, quality control and uncertainty characterization; and improved dataset construction methods