GODAE is sponsored by
Observational data
Delivery of effective ocean products and services requires sustained access to global data of known quality. The global subsurface ocean is chronically undersampled and will remain so for the foreseeable future, but advances in satellite technology and analysis systems that exploit in-situ and satellite observations have brought a revolution to the amount of useful information available at the ocean surface.
Sea Surface Topography (Altimetry)
Ocean currents, driven by wind, tides and gravity keep the ocean in motion and thus constantly change the ocean topography (or global sea surface elevation). GODAE requires global, near real-time, high accuracy and high-resolution observations of sea surface topography.
Oceanographers measure the ocean topography from space using a device called radar altimeter. Radar altimetry can measure the height of the sea surface and detect the slightest variation in ocean levels very accurately. With this information, the growth and evolution of surface waves in response to winds and tidal forcing can be studies, and the dynamic topography can be calculated to derive the positions and intensities of ocean currents, eddies and thermal fronts. It requires at least two (and preferably three) altimeter missions with one very accurate long-term altimeter system to avoid incomplete sampling of high frequency, smaller scale oceanic variability.
Courtesy NASA/JPL-CaltechAfter 2006 there is a very serious issue of continuity and availability. In fact, there may even be a complete gap in available altimeter measurements from 2007 up to the launch of Jason-2 in mid 2008; there will then be only one operating altimeter mission until the NPOESS altimeter (2013), and the present plan for the NPOESS altimeter has it in a different orbit. The consequences of the shift in orbit may be considerable for long-term climate applications. This is very alarming and critical in the light of the fundamental role of altimeters for GODAE and operational oceanography. Given the long lead-times for satellite missions, the urgent attention of nations and their satellite agencies to respond to this situation is needed.
Sea Surface Temperature (SST)
Sea surface temperature (SST) is the water temperature at the surface of the ocean. There are many techniques for measuring SST, ranging from direct (in-situ) measurement, taken from moored or free drifting boys or from ships, to remotely sensed observation using infrared radiometers (different radiometers are using - AVHRR, AVNIR, ATSR or AMSR) which work from satellites. The satellite measurement is made by sensing the ocean radiation in two or more wavelengths in the infrared part of the electromagnetic spectrum which can be then be empirically related to SST. The great advantage of using satellite measurements, is the speed (6-12 hours) and coverage (global, high-resolution) with which the observed data are available for processing.
SST is required by operational ocean and atmospheric forecasting systems to constrain the modelled upper ocean circulation thermal structure and for exchange of energy between the ocean and atmosphere. The high-resolution components of GODAE require global high-resolution sea surface temperature in near real-time for assimilation into ocean models. Remote sensing missions planned in the near future broadly meet GODAE needs in terms of sampling and accuracy.
The GODAE High-Resolution SST Pilot Project (GHRSST-PP) provides a new generation of global coverage high-resolution (<10km) SST data products to the operational oceanographic, meteorological, climate and general scientific community, in real time and in delayed mode.
Surface winds and fluxes
For both analyses and short-range ocean forecasts, GODAE will rely heavily on surface fluxes from a number of NWP centres. Winds or stresses are an important quantity for the initialisation of atmospheric and ocean models.
(Last Updated: 16-10-2007)