The TOGA and WOCE programs used ships-of-opportunity to deploy XBTs along selected routes. These networks, first established in the North Pacific, and then extended to the tropics and other mid-latitude regions, provided the data for observing network design and for fundamental studies of ocean variability and predictability. The tropical network was critical for developing models of ENSO and continues to be an important contribution to the initialization of prediction models. SOOP thermal data also constitute the bulk of the global upper ocean thermal and so represent our "knowledge" of the seasonal cycle and interannual variability.

The Tropical Atmosphere-Ocean array (TAO) was an initiative of TOGA and presently constitutes the core of the (operational) ENSO observing system. Till this point it has been argued that TAO and SOOP are complementary and that any redundancy that does exist could not be removed without significant effort and loss of capability.

In the early 1990s, the US and France launched the Topex/Poseidon altimeter. This instrument delivered, and continues to deliver, estimates of surface topography changes to an accuracy of around 2 cm. This capability, plus the development of skillful model and data assimilation systems, has forever changed the way we gather and interpret information. With such information available it does not make sense to design and evaluate networks in isolation. Networks must be considered as a contribution to a larger, integrated in situ and remote system, with consequences for sampling and design.

There is now also a developing plan for a future global array of profiling floats (Argo). In theory, Argo will deliver an upper ocean (around 1500-2000m) profile of T and S every 10 days or so from around 3000 floats. This will revolutionize the upper ocean observing network.

It is timely then to reconsider the upper ocean sampling network, particularly the SOOP XBT contribution, including salinity sampling where possible. The rationale for the observing network is provided by the CLIVAR IP, OOSDP (1995) plus the action plan for ocean observing system for climate (Sydney Workshop, GOOS publ.)

• Background
• Objectives
• Method
• Atlantic Ocean
• Indian Ocean
• Pacific Ocean
• Workshop