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Surface Water and Ocean Topography Mission (SWOT) Lee-Lueng Fu (Jet Propulsion Laboratory)

Surface Water and Ocean Topography Mission (SWOT) Lee-Lueng Fu (Jet Propulsion Laboratory). A snapshot of sea surface height anomalies from T/P and ERS altimeters. Spatial scales of the AVISO T/P-ERS merged data. Overlapping at 150 km. 210 km. T/P along-track. T/P-ERS mapped. km.

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Surface Water and Ocean Topography Mission (SWOT) Lee-Lueng Fu (Jet Propulsion Laboratory)

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  1. Surface Water and Ocean Topography Mission (SWOT) Lee-Lueng Fu (Jet Propulsion Laboratory)

  2. A snapshot of sea surface height anomalies from T/P and ERS altimeters

  3. Spatial scales of the AVISO T/P-ERS merged data Overlapping at 150 km 210 km T/P along-track T/P-ERS mapped km Correlation of SSH time series as function of spatial separation A spatial scale computed as follows: T/P mapped L= 210 km Scales shorter than 150-200 km are not resolved. SSH wavenumber spectra (Ducet et al. 2000)

  4. Small-scale Variability of the Ocean Unresolved by Nadir-looking Altimeter ground tracks of Jason (thick) and T/P (thin) Tandem Mission 10 km scale eddies Resolvable by HM 100 km scale eddies resolvable by WSOA 100 km

  5. Coastal currents have scales less than 10 km 42.5º N  h ~ 5 cm  v ~ 50 cm/sec < 10 km < 10 km 41.9º N < 10 km Observations made by ADCP offshore from the US West Coast T. Strub

  6. 8 7 6 5 4 3 2 1 Number of Observation SWOT Measurement Concept A SAR interferometry radar altimeter Near-global coverage with 16-day repeat orbit • Same technique as WSOA – radar interferometry • Use of SAR to enhance the along-track resolution • 2 cm measurement precision at 2 km resolution • 1 micro-radian precision in mean sea surface slope at 2 km resolution • No data gap near the coast

  7. SWOT Orbit Sampling Observations/cycle

  8. Altimetry SSH wavenumber spectrum T/P Jason pass 132 (147 cycle average) ? Power density (cm2/cycles/km) Noise level of HM for 2 cm measurement noise at 2 km resolution T/P ? Wavenumber (cycles/km) Much reduced noise floor will enable the study of the spectrum at sub-mesoscales which have not been well resolved from existing data. Stammer (1997)

  9. Geostrophic velocity error spectrum 100 50 25 km = 2cm/7km = 2cm/2km (or 1 cm/7km) Velocity error (cm/s)2/cyc/km = 1cm/km (or 0.4 cm/7km) Wavenumber (cyc/km) For the three cases, velocity error is reduced from 7.8 to 3.6, 1.3 cm/sec at 25 km resolution; or 27, 15, 5 cm/sec at 10 km resolution

  10. Sub-mesoscale variability Radius of deformation Radius of deformation Sub-mesoscale processes are poorly observed but important to the understanding of the dissipation mechanism of ocean circulation. McWilliams (2006)

  11. Hydrology applications • Our knowledge of the spatial and temporal distribution of surface waters is poor • Unconfined hydraulics of wetlands • Lakes and reservoirs are globally distributed but not measured • Under-developed economic and political infrastructures • Hydrologic Science and Applications Issues: • Need to constrain water and energy cycle models with surface water discharge and storage changes, globally & consistently • Improve understanding of flow hydraulics, especially for flood hazards • Trans-boundary water flows are poorly known but critical for water resource management

  12. High-resolution ocean surface topography workshop SWOT is based on the technology of SRTM and WSOA. WATER Mission was developed for hydrology SWOT is recommended by the Decadal Survey as a combined mission for oceanography and hydrology. A Science Working Group has been formed with additional ~200 participants from ~30 countries, and growing!

  13. Errors in coastal tide models up to 20 cm are revealed from the Jason-T/P Tandem Mission. What is the state of the art in coastal tide modeling? Andersen and Egbert (2005)

  14. Besides the intrinsic science of internal tides, they introduce 2-5 cm/sec error in ocean current velocity. Is predicting internal tides from models feasible ? R. Ray/GSFC

  15. Wet Tropospheric Corrections • Land contamination in microwave radiometer observations • OSTM has the potential for pushing the limit of coastal distance to 10 km in favorable conditions • What are the energy containing scales of water vapor in coastal zones? • How good is model analysis of water vapor in coastal zones? • What new technologies are feasible for making high-resolution water vapor measurements?

  16. Conclusions • UsingSAR interferometry, SWOT has the capability of mapping ocean topography at 1 km resolution next to the coast. • Coastal tides: need models with much improved accuracies. • Internal tides: sources of mixing in the ocean which is linked to the overall meridional overturning circulation. Also sources of errors for estimating ocean current velocity if not corrected. Need developing predictive models. • Wet tropospheric corrections: Need to assess (1) the performance of mesoscale meteorological analysis in coastal zones, (2) new technologies for making high-resolution water vapor measurements.

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