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

2. EGU Vienna, April 2012 2DTU Space, Technical University of Denmark Outline •What Cryosat offers •Cryosat Problems:”Mode jumps” •The Baffin Bay test. •Retracking of Cryosat-2 SAR •Towards DTU12

3. EGU Vienna, April 2012 3DTU Space, Technical University of Denmark 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) Should improve gravity substantially

4. EGU Vienna, April 2012 4DTU Space, Technical University of Denmark 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 Satellite orbit Altitude (H) Range (R) Reference ellipsoid Geoid Sea surface

5. EGU Vienna, April 2012 5DTU Space, Technical University of Denmark Mode – jumps Cryosat ESA L2 GDR SAR+LRM in the Arctic South North Large ”jumps” at mode shift Different between processors LRMSAR SAR-In

6. EGU Vienna, April 2012 6DTU Space, Technical University of Denmark Baffin Bay •Interesting because its partly icecovered. •This enables comparison C2 SAR and LRM

7. EGU Vienna, April 2012 7DTU Space, Technical University of Denmark Cryosat SAR + LRM Entire 2011 LRM mode (summer) SAR mode (winter)

8. EGU Vienna, April 2012 8DTU Space, Technical University of Denmark Retracking of Cryosat-2 SAR Experimenting with 5 retrackers on 1 year Level 1b SAR waveform (black) Entire waveform: OCOG + 5 parameter beta retracker with exp tail (blue) and threshold retracking. Leading Edge: OCOG and threshold retracking (50% for SAR) (Se Poster XY348 by M. Jain today) 50% Th- reshold OCOG LE OCOG Range bin

9. EGU Vienna, April 2012 9DTU Space, Technical University of Denmark Retracking 1 Year 20 Hz SAR data only SSH data in leads used 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 Leads defined by ERS-L2 data.

10. EGU Vienna, April 2012 10DTU Space, Technical University of Denmark ERS GM ENVISAT+GFO ERM ICESATGEOSAT GM CESAT

11. EGU Vienna, April 2012 11DTU Space, Technical University of Denmark Gravity comparison Identical parameter set to DTU10 for gravity comparison. 6696 obsMaxStd EGM2008545.51 DTU10474.89 ESA L2 SAR444.66 NOAA LRM (2 month)454.68 Entire WF retrack OCOG Beta 5 param Treshold 46 42 41 4.74 4.19 4.12 Lead Edge retrack OCOG Treshold 39 4.01 3.96 OCOG SAR & SAR-in383.96 Getting a 30% improvement

12. EGU Vienna, April 2012 12DTU Space, Technical University of Denmark Coastal regions heavily improved DTU 2012 Beta 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. StandardsDNSC08/DTU10DTU12 Beta Dry troposphereECMWF Wet troposphereECMWFRadiometer IonosphereAltimeter Dynamic AtmosphereIB (1013 mbar)MOG-2D_IB Ocean tidesGOT 00.2GOT4.7 Sea State BiasBM4Non-PARAM Aim to release DTU12 at ”20 years of progress” in september 2012

13. EGU Vienna, April 2012 13DTU Space, Technical University of Denmark Coastal regions heavily improved All > 10.000 obsDTU12DTU10SAND 18EGM2008 Purple (0-20 m DEPTH)3.013.303.69 3.20 Dark Blue (20-50 m)2.79 3.42 2.80 Light Blue (50-200 m)3.223.273.52 3.23 Green (200-500 m)3.533.493.79 3.51 Yellow (500-1000 m)4.334.304.35 Red/Pink (>1000 m)4.834.824.69 4.85 All 321.0003.723.814.093.83 DTU 2012 Beta Preliminary North Atlantic field including 1.6 years of NOAA C2 LRM Data (30% data increase) Getting a 4-10% improvement

14. EGU Vienna, April 2012 14DTU Space, Technical University of Denmark 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)