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Increasing the accuracy of Arctic gravity field modelling using Cryosat-2 SAR altimetry.

Increasing the accuracy of Arctic gravity field modelling using Cryosat-2 SAR altimetry. Ole B. Andersen, L. Stenseng and J. Maulik. Outline. What Cryosat offers Cryosat Problems:”Mode jumps” The Baffin Bay test. Retracking of Cryosat-2 SAR Towards DTU12. Cryosat.

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Increasing the accuracy of Arctic gravity field modelling using Cryosat-2 SAR altimetry.

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  1. Increasing the accuracy of Arctic gravity field modelling using Cryosat-2 SAR altimetry. Ole B. Andersen, L. Stenseng and J. Maulik

  2. Outline • What Cryosat offers • Cryosat Problems:”Mode jumps” • The Baffin Bay test. • Retracking of Cryosat-2 SAR • Towards DTU12

  3. Cryosat Offers a factor of two in SSH accuracy 369 Day repeat (similar to ERS-GM) SAR in Arctic+Coastal -> Alongtrack res improved Important for shallow water (upward continuation) Shouldimprovegravitysubstantially

  4. Satellite orbit Altitude (H) Range (R) Sea surface Geoid Reference ellipsoid The (mean) Sea surface height mimicks the geoid Gravity from MDT corrected MSS (= Geoid) Laplace 1 mGal -> Alongtrack heights differences over 10 km need to be accurate to <1 cm

  5. Mode – jumps Cryosat ESA L2 GDR SAR+LRM in the Arctic LRM SAR SAR-In Large ”jumps” at mode shift Different between processors South North

  6. Baffin Bay • Interestingbecauseitspartlyicecovered. • Thisenablescomparison C2 SAR and LRM

  7. Cryosat SAR + LRMEntire 2011LRM mode (summer)SAR mode (winter)

  8. Retracking of Cryosat-2 SAR 50% Th- reshold LE OCOG OCOG Range bin Experimenting with 5 retrackers on 1 year Level 1b SAR waveform (black) Entire waveform: OCOG + 5 parameter betaretracker with exp tail (blue) and thresholdretracking. Leading Edge: OCOG and thresholdretracking (50% for SAR) (Se Poster XY348 by M. Jain today)

  9. Retracking 1 Year 20 Hz SAR dataonly SSH data in leads used Leads defined by ERS-L2 data. Highpass to 100 km Std (ESA L2 GDR) = 17.5 cm Std (Leading Edge OCOG) = 11.1 cm Std (Leading Edge Treshold) = 10.8 cm

  10. ERS GM ENVISAT+GFO ERMICESAT GEOSAT GMCESAT

  11. Gravity comparison Identical parameter set to DTU10 for gravity comparison. Getting a 30% improvement

  12. DTU 2012 Beta Coastal regions heavily improved Including CRYOSAT LRM data (ESA L2 vs NOAA) Including CRYOSAT SAR data Currently testing Cryosat SAR-IN Working on adjust ”mode jumps” Updating all existing GM data. Aim to release DTU12 at ”20 years of progress” in september 2012

  13. DTU 2012 Beta Coastal regions heavily improved Preliminary North Atlantic field including 1.6 years of NOAA C2 LRM Data (30% data increase) Getting a 4-10% improvement

  14. Summary CRYOSAT-2 Succesful retracking of SAR data. SAR-In: Currently working on retracking LRM: we can currently not compare with ERS-L2 GDR. Dramatic improvement in the Arctic Ocean (factor of 1.3) Problems with mode jumps – ESA but also our own retracker. In global ocean we only se marginal improvement, but more improvement to come once we ”have gained experience” The new Jason EOL Geodetic Mission will complement Cryosat. Will be fantastic for the future. Acknowledgement: Support/data and coorporation with the NGA (US)

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