To gather long-term information about the global ocean and currents, orbiting instruments must take extremely precise measurements of the height of the ocean surface - commonly called sea level - above the center of the Earth. This is referred to as ocean surface topography; not to be confused with bathymetry, which is the topographic relief on the bottom of the ocean. Ocean surface topography data contain information that has significant practical applications in such areas as the study of worldwide weather and climate patterns, the monitoring of shoreline evolution, and the protection of our great ocean fisheries. There are many scientists studying this information.
Ocean topography missions like Jason-1, OSTM/Jason-2, and Jason-3 seek to satisfy the following science goals:
- To determine general ocean circulation, and to understand its role in Earth's climate, and its hydrological and biogeochemical cycles;
- To study the variation of ocean circulation on time scales from seasonal and annual to decadal and its effects on climate change;
- To collaborate with other global ocean monitoring programs to produce routine models of the global ocean for scientific and operational applications;
- To study large-scale ocean tides;
- To study geophysical processes from their effects on ocean surface topography.
More than 28 years of scientific discovery by NASA’s ocean altimetry satellites has broadened the depth of science objectives for the missions. The Jason missions are now expected to:
- Measure global sea-height change and provide a continuous view of changing global ocean surface topography;
- Calculate the transport of heat, water mass, nutrients, and salt by the ocean;
- Increase understanding of ocean circulation and seasonal changes and how the general ocean circulation changes through time;
- Contribute to monitoring and study of marine weather by providing estimates of significant wave height and wind speeds over the ocean;
- Test how we compute ocean circulation caused by blowing winds;
- Improve the knowledge of ocean tides and develop open-ocean tide models;
- Improve forecasting of climatic events like El Niño and of global climate in general;
- Describe the nature of ocean dynamics and develop a global view of Earth's ocean;
- Monitor the variation of global mean sea level and its relation to global climate change;
- Measure cloud liquid water and water vapor in the atmosphere over the ocean; and
- Support weather forecasting and climate studies by measuring the temperature and humidity of the atmosphere as a function of elevation using the occultation of GNSS signals.