160
L.-L. Fu
energy in spectral space has led to a surprising finding of inverse cascade of energy
associated with the first baroclinic mode of the ocean.
The specific orbit choice of T/P and its follow-ons has led to the most accurate
knowledge of the surface (or barotropic) tides in the open ocean. The calculation
of the energy flux of the tides proves that half of the energy required to mix ocean
waters to maintain the large-scale thermohaline circulation comes from tidal dissipation in the deep ocean. The finding of internal tides in altimetry data is another
surprise that creates a new surge of studies of the subject of fundamental importance
in ocean mixing and tidal energy cycle.
A limitation of the conventional nadir-looking altimeter is its sampling in space
and time. With data merged from two altimeters, the decade-long data set that has
made great strides in advancing our knowledge of ocean circulation has a spatial resolution that prevents observation of the important sub-mesoscale processes at scales
shorter than 100 km. A way to advance the capability of future altimetry is the use
of radar interferometry for making high-resolution wide-swath altimetry measurement. The SWOT Mission recommended by the US National Research Council’s
Decadal Survey is taking on this challenge by developing a Ka-band radar interferometry system for flight in the late 2010s. SWOT measurement will significantly
advance both oceanography and land hydrology and address two key aspects of climate change: improving the prediction of the rate of warming through improved
understanding of the oceanic submesoscale processes, and improving the capability of monitoring and managing the shifting water resources caused by a warming
climate.
By providing wide-swath coverage, a single mission like SWOT is equivalent to
more than 10 conventional nadir-looking altimeters. After the demonstration of its
workings, radar interferometry is potentially a candidate for replacing nadir-looking
altimetry as a standard tool for oceanographic and hydrological applications.
Acknowledgements The research presented in the paper was carried out at the Jet Propulsion
Laboratory, California Institute of Technology, under contract with the National Aeronautic and
Space Administration. Support from the Jason-1 and OSTM/Jason-2 Projects is acknowledged.
References
Ablain M, Cazenave A, Valladeau G, Guinehut S (2009) A new assessment of the error budget
of global mean sea level rate estimated by satellite altimetry over 1993–2008. Ocean Sci 5:
193–201
Alsdorf D, Fu LL, Mognard N, Cazenave A, Rodriguez E, Chelton D, Lettenmaier D (2007)
Measuring the global oceans and terrestrial fresh water fromspace. EOS Trans AGU 88(24):253
Bamber JL, Riva REM, Vermeersen BLA, LeBrocq AM (2009) Reassessment of the potential sea-level rise from a collapse of the West Antarctic ice sheet. Science 324:901–903,
doi:10.1126/science.1169335
Carrère L, Lyard F (2003) Modeling the barotropic response of the global ocean to atmospheric
wind and pressure forcing – comparisons with observations. Geophys Res Lett 30:1275,
doi:10.1029/2002GL016473
Cazenave A, Nerem RS (2004) Present-day sea level change: observations and causes. Rev
Geophys 42:RG3001, doi:10.1029/2003RG000139
L.-L. Fu
energy in spectral space has led to a surprising finding of inverse cascade of energy
associated with the first baroclinic mode of the ocean.
The specific orbit choice of T/P and its follow-ons has led to the most accurate
knowledge of the surface (or barotropic) tides in the open ocean. The calculation
of the energy flux of the tides proves that half of the energy required to mix ocean
waters to maintain the large-scale thermohaline circulation comes from tidal dissipation in the deep ocean. The finding of internal tides in altimetry data is another
surprise that creates a new surge of studies of the subject of fundamental importance
in ocean mixing and tidal energy cycle.
A limitation of the conventional nadir-looking altimeter is its sampling in space
and time. With data merged from two altimeters, the decade-long data set that has
made great strides in advancing our knowledge of ocean circulation has a spatial resolution that prevents observation of the important sub-mesoscale processes at scales
shorter than 100 km. A way to advance the capability of future altimetry is the use
of radar interferometry for making high-resolution wide-swath altimetry measurement. The SWOT Mission recommended by the US National Research Council’s
Decadal Survey is taking on this challenge by developing a Ka-band radar interferometry system for flight in the late 2010s. SWOT measurement will significantly
advance both oceanography and land hydrology and address two key aspects of climate change: improving the prediction of the rate of warming through improved
understanding of the oceanic submesoscale processes, and improving the capability of monitoring and managing the shifting water resources caused by a warming
climate.
By providing wide-swath coverage, a single mission like SWOT is equivalent to
more than 10 conventional nadir-looking altimeters. After the demonstration of its
workings, radar interferometry is potentially a candidate for replacing nadir-looking
altimetry as a standard tool for oceanographic and hydrological applications.
Acknowledgements The research presented in the paper was carried out at the Jet Propulsion
Laboratory, California Institute of Technology, under contract with the National Aeronautic and
Space Administration. Support from the Jason-1 and OSTM/Jason-2 Projects is acknowledged.
References
Ablain M, Cazenave A, Valladeau G, Guinehut S (2009) A new assessment of the error budget
of global mean sea level rate estimated by satellite altimetry over 1993–2008. Ocean Sci 5:
193–201
Alsdorf D, Fu LL, Mognard N, Cazenave A, Rodriguez E, Chelton D, Lettenmaier D (2007)
Measuring the global oceans and terrestrial fresh water fromspace. EOS Trans AGU 88(24):253
Bamber JL, Riva REM, Vermeersen BLA, LeBrocq AM (2009) Reassessment of the potential sea-level rise from a collapse of the West Antarctic ice sheet. Science 324:901–903,
doi:10.1126/science.1169335
Carrère L, Lyard F (2003) Modeling the barotropic response of the global ocean to atmospheric
wind and pressure forcing – comparisons with observations. Geophys Res Lett 30:1275,
doi:10.1029/2002GL016473
Cazenave A, Nerem RS (2004) Present-day sea level change: observations and causes. Rev
Geophys 42:RG3001, doi:10.1029/2003RG000139