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  • This slide shows the space and time sampling of satellite altimeters . Before I explain how SWOT works, let me briefly go over what has been observed in the existing altimetry data and what has been missing from it
  • The technique for the new observation is radar interferometry, first demonstrated by JPL’s SRTM.

SWOT_Fu_2011_IGARSS.ppt SWOT_Fu_2011_IGARSS.ppt Presentation Transcript

  • SWOT: A HIGH-RESOLUTION WIDE-SWATH ALTIMETRY MISSION FOR OCEANOGRAPHY AND HYDROLOGY Lee-Lueng Fu, Ernesto Rodriguez, JPL/Caltech Douglas Alsdorf, Ohio State University Rosemary Morrow, Nelly Mognard, CNES 2011 IGARSS Vancouver, Canada July 25-29, 2011
    • SWOT (Surface Water and Ocean Topography) is a satellite mission being jointly developed by NASA and CNES with contributions from CSA. Expected launch date is in 2019.
    • Science Goals –
    • (1) study hydrological processes by determining the storage and discharge rate of water on land.
    • (2) study the oceanic mesoscale and submesoscale processes that determine the kinetic energy of ocean circulation and its transport of water properties.
    • Societal Benefits – Address two key issues facing a warming planet:
    • (1) the variability of fresh water resources.
    • (2) the capacity of ocean circulation in regulating the rate of warming.
    • Technology Goals – Set the standard for future operational altimetry missions.
    A Mission in Development
    • SWOT will measure water storage change (ΔS ) to better than 10% for lakes 250m by 250m in size.
    • SWOT will measure ΔS in ~30 million lakes, globally; accounting for as much as 80% of the world’s changing surface water volume.
    Water Storage in Lakes
    • Arctic lakes are
    • disappearing as
    • permafrost melts
  • Expected SWOT Sampling in North America
    • Floods are poorly measured whereas flow information from rivers crossing international boundaries is rarely shared.
    • SWOT will measure river hydraulic parameters for estimating river discharge.
    • SWOT will measure flood waves and estimate discharge along entire networks of rivers, globally.
    Coverage by OSTM/Jason-2 River Flow and Discharge Rates
  • SWOT WSOA Space time sampling of radar altimetry missions 10 100 days 1000 km 100 km 10 km 1 km
  • cm TOPEX/Poseidon & ERS Data Cheney et al 1983 Ducet et al 2000 Mapping Global Ocean Eddy Variability
  • Ocean Currents and Eddies Have Small Scales Conventional altimeters resolve only the large mesoscale eddies (Jason-2/Envisat) High-resolution ocean models suggest a ubiquitous presence of submesocale eddies 50% of the vertical exchange of heat and dissolved CO2 takes place at the submesoscales. ECCO2 Deepwater Horizon oil spill
  • h= H –r 1 cos( Ө ) δ h = r 1 δ θ sin( θ ) = [r 1 tan( θ ) λ /2 π B] δφ Off-nadir height measurement achieved via radar interferometry High-resolution along flight via Doppler shift in frequency High resolution achieved via Synthetic Aperture Radar
  • Radar Interferometry was successfully demonstrated by JPL’s Shuttle Radar Topography Mission (SRTM) 60m X/C band (3-6 cm wavelengths)
  • The SWOT Mission Configuration Ka band (0.85 cm wavelength) Nadir interferometry signals enhanced by a nadir receiver
  • SWOT noise spectrum SSH wavenumber spectrum 1000 100 25 10 km SWOT resolution k -4 k -2 Assemblage of ocean spectra Jason noise floor
  • SWOT Sampling characteristics (78 deg inclination, 22 day repeat orbit)
  • Additional Applications Sea Ice Freeboard Ocean Bathymetry Ice Sheet Topography
    • Summary
    • SWOT will provide a revolutionary set of measurements of the elevation of land surface water and ocean topography globally.
    • The high-resolution swath measurements will resolve lakes of 250m x 250m area and rivers of 100 m width, and oceanic eddies of 10-km wavelength.
    • The unprecedented resolution and coverage of SWOT will enable breakthroughs in understanding the balance of water budget on land and energy budget of ocean circulation.
    • Significant improvements are expected in ocean modeling for predicting future climate and in fresh water management in response to climate change.
    • Other applications include ocean bathymetry, sea ice thickness, ice sheet topography, coastal processes, etc.