The marine environment plays an increasingly important role in shaping economies and infrastructures, and touches upon many aspects of our lives, including food supplies, energy resources, national security and recreational activities. Global Ocean Data Assimilation Experiment (GODAE) and GODAE OceanView have provided platforms for international collaboration that significantly contribute to the scientific development and increasing uptake of ocean forecasting products by end users who address societal issues such as those listed above. Many scientific challenges and opportunities remain to be tackled in the ever-changing field of operational oceanography, from the observing system to modelling, data assimilation and product dissemination. This paper provides a brief overview of past achievements in GODAE OceanView, but subsequently concentrates on the future scientific foci of GODAE OceanView and its Task Teams, and provides a vision for the future of ocean forecasting.

Real-time operational predictions of the major ocean basins which resolve the ocean mesoscale at mid-latitudes have become established in more than a dozen countries over the last 15 years. These predictions depend on the global ocean observing system (particularly satellite altimeters and the Argo profiling float system), high performance computers and sophisticated ocean models and data assimilation systems. They support an expanding range of information services for operations at sea, weather forecasts and protection of the environment. GODAE Oceanview (GOV) assists the groups developing these predictions. This paper provides an introduction to GOV and the papers in this special issue.

Several systems to compute routinely ocean forecasts have been developed within the Global Ocean Data Assimilation Experiment (GODAE). They are used to deliver operational services. The cornerstones of these systems are: (1) input high quality observations obtained from space and in situ, available shortly after the measurement is done, (2) state-of-the-art realistic numerical model configurations, and (3) efficient assimilation system that combine the observations and the model physics. To be operated routinely, these components have to be integrated into a whole system that will enable routine operations, and service delivery in real-time. We present here these functions, highlighting their specific characteristics.

Although many oceanographic data products are now considered operational, continued dialogue between data producers and their user communities is still needed. The fisheries and environmental science communities have often been criticized for their lack of multidisciplinarity, and it is not clear whether recent developments in operational oceanographic products are addressing these needs. The International Council for the Exploration of the Sea (ICES) Working Group on Operational Oceanographic products for Fisheries and Environment (WGOOFE) identified a potential mismatch between user requirements and the perception of requirements by the providers. Through a questionnaire (98 respondents), WGOOFE identified some of these issues. Although products of physical variables were in higher demand, several biological parameters scored in the top 10 rankings. Users placed specific focus on historic time series products with monthly or annual resolution and updating on similar time scales. A significant percentage requested access to numerical data rather than graphical output. While the outcomes of this survey challenge our views of operational oceanography, several initiatives are already attempting to close the gap between user requirements and products available.

Assimilation systems synthesize diverse in-situ and satellite data streams into full four-dimensional state estimates by combining the strengths of each data set and also of the model. The resulting analysis provides an integrated view of the information in the various observations as well as derived estimates of unobserved quantities. Assimilation systems are particularly important for the ocean where subsurface observations, even today, are sparse and intermittent compared with the scales needed to represent ocean variability and where satellites only sense the surface. Increasingly, models and assimilation systems are being used to provide information about the current observing system and to help in the design plans for new observations. Whether it is as a user of observations or a contributor to evaluation of the observing system, ocean synthesis and assimilation systems are now an integral part of the global ocean observing and information system. Major advances have been made over the last decade under the auspices of WCRP's Climate Variability and Predictability Project (CLIVAR) and the Global Ocean Data Assimilation Experiment (GODAE). In addition to advances in the assimilation systems, there have been major developments in the observing system, with satellite altimetry, the tropical moored buoy arrays in the Pacific and Atlantic, and more recently Argo. These developments have led to significant advances in our understanding and prediction of ocean variations at both mesoscale and climate scales. Many challenges remain. Some of these challenges lie in the observations themselves, some in the assimilation systems that, even in the more recent era of unprecedented observations from satellite altimetry and Argo, provide different views of climate variations. Yet there are many examples of successful applications from ocean assimilation products. Use of these systems for assessing the observing system helps identify the strengths of each observation type, and indicates that none of the current observations is redundant. Indeed, the indication is that the ocean remains under-sampled and that further improvements in the observing system are needed for both climate monitoring and prediction. Future developments will be increasingly towards consistent analyses across components of the Earth system using, e.g., coupled atmosphere-ocean models.

(1) Centre for Australian Weather and Climate Research, A partnership of the Bureau of Meteorology and CSIRO, Melbourne 3001, Victoria, Australia, Email: g.brassington@bom.gov.au (2) Met Office, FitzRoy Road, Exeter, Devon EX1 3PB, United Kingdom, Email: adrian.hines@metoffice.gov.uk (3) Mercator Océan, Parc Technologique du Canal, 8-10 rue Hermès, 31520 Ramonville St Agne, France, Email: Eric.Dombrowsky@mercator-ocean.fr (4) Office of Global Environment and Marine Department, Japan Meteorological Agency, 1-3-4 Otemachi, Chiyoda-ku, Tokyo, Japan, Email: s_ishizaki@met.kishou.go.jp (5) Naval Oceanographic Office, Stennis Space Center, MS 39529, USA, Email: Frank.Bub@navy.mil (6) Fleet Numerical Meteorology and Oceanography Center, 7 Grace Hopper Avenue, Monterey, CA 93943, USA, Email: Mark.Ignaszewski@navy.mil

Global ocean forecast systems, developed under the Global Ocean Data Assimilation Experiment (GODAE), are a powerful means of assessing the impact of different components of the Global Ocean Observing System (GOOS). Using a range of analysis tools and approaches, GODAE systems are useful for quantifying the impact of different observation types on the quality of analyses and forecasts. This assessment includes both existing and future observation platforms. Many important conclusions can be drawn from these studies. It is clear that altimeter data are extremely important for constraining mesoscale variability in ocean forecast systems. The number of altimeters is also important. For example, near-real-time applications need data from four altimeters to achieve skill that is similar to systems using data from two altimeters in delayed mode. Another important result is that sea surface temperature is the only observation parameter that adequately monitors ocean properties in coastal regions and shallow seas. Assimilation of Argo data provides a significant, measurable improvement to GODAE systems, and is the only observation platform that provides global-scale information for constraining salinity. The complementary nature of different components of GOOS is now clear and the emergence of new assimilation techniques for observing system evaluation provides the GODAE community with a practical path toward routine GOOS monitoring.

During the last 15 years, operational oceanography systems have been developed in several countries around the world. These developments have been fostered primarily by the Global Ocean Data Assimilation Experiment (GODAE), which coordinated these activities, encouraged partnerships, and facilitated constructive competition. This multinational coordination has been very beneficial for the development of operational oceanography. Today, several systems provide routine, real-time ocean analysis, forecast, and reanalysis products. These systems are based on (1) state-of-the-art Ocean General Circulation Model configurations, either global or regional (basin-scale), with resolutions that range from coarse to eddy-resolving, and (2) data assimilation techniques ranging from analysis correction to advanced three- or four-dimensional variational schemes. These systems assimilate altimeter sea level anomalies, sea surface temperature data, and in situ profiles of temperature and salinity, including Argo data. Some systems have implemented downscaling capacities, which consist of embedding higher-resolution local systems in global and basin-scale models (through open boundary exchange of data), especially in coastal regions, where small scale-phenomena are important, and also increasing the spatial resolution for these regional/coastal systems to be able to resolve smaller scales (so-called downscaling). Others have implemented coupling with the atmosphere and/or sea ice. This paper provides a short review of these operational GODAE systems.