Sea surface temperature. GODAE has a requirement for high-resolution global real-time products. A representative resolution would be 5-10 km, ideally with resolution of the diurnal cycle (say 6 hr), and the desired accuracy is 0.1-0.2oC. No such product exists at this time. Further progress requires consideration of products based on information merged from different platforms and/or instruments. A further issue is the need to keep the data set consistent with the broad-scale in situ network. Discussions are underway to realize such a product in time for GODAE
Surface short wave radiation. If sea surface temperature is used as a strong constraint on the models (that is, it is assumed to be near-perfectly known), then knowledge of the net downward short-wave radiation completes the determination of the thermal boundary conditions (strictly speaking, it is treated as an internal heating source). No requirements for a global, real-time product were given to the database but scales of around 2-300 km, daily are desirable. Such a product makes demands outside the immediate community of GODAE (satellite clouds, aerosols, etc.) and will require careful direct measurements for validation. It may be satisfactory, for quick-look products, to compromise the quality. For delayed-mode GODAE would be seeking accuracy of around 10-15 W/m2.
Surface/dynamic topography. Altimetry has had an immense impact on oceanography and is a key strategy for GODAE. However, in order to exploit its true potential, vastly improved monitoring of the subsurface ocean is required. GODAE, in collaboration with the Climate Variability and Predictability Programme (CLIVAR) has embarked on a several-fold enhancement of present capabilities in a project known as Argo, using a profiling float. The targetted sampling is around 3000 floats globally measuring temperature and salinity over the upper 2000 m once every 10 days. With altimetric missions such as Jason, Argo will be able to provide a key part of the data input requirements for GODAE. Figure 1 juxtaposes a hypothetical distribution of floats against a typical sampling realised by today's altimetric instruments. The US has already committed significant resources to this proposal.
There are of course many other important remote and direct measurements required for GODAE. Special efforts may be mounted to develop high quality, accurate merged global wind stress products. The International GODAE Steering Team has also noted ocean color may be required in order to parameterize ocean transparency.
Schematic showing a hypothetical global distribution
of profiling floats (around3000, randomly distributed, shown as red dots)
superimposed on the Topex/Poseidon sea level anomaly for Cycle 212, 16-22
June, 1998 (from JPL).
