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Ocean Surface Topography from Space
Wide swath altimetry for high resolution oceanography and hydrology: the SWOT mission
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Nelly Mognard

Paul Bates
(University of Bristol)
Lee-Lueng Fu
(California Institute of Technology - JPL)
Douglas Alsdorf
Ernesto Rodriguez
(California Institute of Technology - JPL)


A critical drawback of profiling altimeters for the ocean is the 200 to 300 km spacing between orbital tracks that prevents sampling of two-dimensional currents and oceanic mesoscale processes that contain 90% of the kinetic energy. In contrast to ocean observations, surface fresh water measurements are limited mostly to in-situ networks of gauges that record water surface elevations at fixed points along river channels. The SWOT (Surface Water Ocean Topography) mission will provide a global coverage and improved resolution that will revolutionize the ocean and hydrology communities.

The SWOT mission ocean science questions are:

  1. What is the small-scale (1-100 km) variability of ocean surface topography that determines the velocity of ocean currents? How are fronts and eddies formed and evolving? How is oceanic kinetic energy dissipated?
  2. What is the synoptic variability of coastal currents? How do the coastal currents interact with the open ocean variability? What are the effects of coastal currents on marine life, ecosystems, waste disposal, and transportation?
  3. How does the small-scale ocean variability interact with the atmosphere? Does this interaction provide a mechanism of dissipation of ocean kinetic energy? How does a hurricane interact with the small-scale variability of the upper ocean heat storage? What is the ocean's dynamic response to hurricanes? How is the new knowledge to be used to improve hurricane forecast?
  4. How do changes in the global water cycle, both natural and anthropogenic, lead to sea level change? How do variations in continental water discharge contribute to sea level change? What role does the storage of water in artificial reservoirs and lakes play in the sea level change budget? How do variations in coastal sea level change affect predictions of water inundation due to sea level rise and/or storm surge.
The SWOT mission hydrology science questions are:
  1. What is the spatial and temporal variability in the world's terrestrial surface water storage and discharge? How can we predict these variations more accurately?
  2. How much water is stored on a floodplain and subsequently exchanged with its main channel? How much carbon is potentially released from inundated areas?
  3. What are the policy implications that freely available water storage data would have for water management? Can health issues related to waterborne diseases be predicted through better mappings?
In addition to oceanography and land hydrology, the proposed measurements will break new ground for studying the dynamics of estuary processes and will provide new information about marine gravity, ocean bathymetry, and glacier and sea ice.

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