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Global altimetric marine gravity field mapping The impact of Cryosat-2 Ole B. Andersen and L. Stenseng.

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Presentation on theme: "Global altimetric marine gravity field mapping The impact of Cryosat-2 Ole B. Andersen and L. Stenseng."— Presentation transcript:

1 Global altimetric marine gravity field mapping The impact of Cryosat-2 Ole B. Andersen and L. Stenseng

2 EGU Vienna, April DTU Space, Technical University of Denmark Outline Satellite altimetry – State of the art gravity Cryosat-2 (what it offers). Noise estimation (20 Hz vs 1 Hz) for Gravity DTU12 Beta.

3 EGU Vienna, April DTU Space, Technical University of Denmark Satellite orbit Altitude (H) Range (R) Reference ellipsoid Geoid Sea surface Altimetry – basic principles

4 EGU Vienna, April DTU Space, Technical University of Denmark The (mean) Sea surface height mimicks the geoid Gravity from MDT corrected MSS (= Geoid) Laplace sea mount Gravity field 1 mGal -> Alongtrack heights differences need to be accurate to <1 cm Rule of Thumb: 1 cm Height difference over 10 km equals 1 mGal.

5 EGU Vienna, April DTU Space, Technical University of Denmark obsMean Std Dev. Max DevNote KMS DNSC08 DTU Double Retrack SS V GSFC NTU SS V16.1 SS V Retracked ERS1+GSA State of the Art:

6 EGU Vienna, April DTU Space, Technical University of Denmark Cryosat ”promises” Factor of 2 on accuracy over conventional altimetry Accuracy independent of Sea state: Jason-1: 1 Hz (altim noise = 1.5 cm): 20 Hz = 6.4 cm C2 DD: 1 Hz (altim noise = 0.75 cm): 20 Hz LRM = 3.2 cm (sqrt averaging) Conventional DD Cryosat

7 EGU Vienna, April DTU Space, Technical University of Denmark C2 will improve Shortwavelength scale signal Bathymetry -> oceanography Long wavelength signal still in error.

8 EGU Vienna, April DTU Space, Technical University of Denmark ESA Level 2 Products. (20 Hz data) Identical profile 2011 / 2012 SAR-In SAR LRM Hawaii

9 EGU Vienna, April DTU Space, Technical University of Denmark 18 Hz Cryosat ”Noise” (Standard Dev)LRMSARSAR-In 2011 Proc 2.1 (20Hz)6.9 cm13.46 cm27.1 cm 2012 Proc 2.4 (20 Hz)10.1 cm9.9 cm14.3 cm SOUTH North Large ”jumps” at mode shift LRMSAR SAR-In 2011 V V 2.4 >100 mGal

10 EGU Vienna, April DTU Space, Technical University of Denmark 1 Hz ”Noise”Entire profileNorth part (42->) L2 – Proc cm2.4 cm (no jumps) L2 – Proc cm3.1 cm RADS cm

11 EGU Vienna, April DTU Space, Technical University of Denmark ERS-1GEOSATERMCRYO-2 Number Std All / Alongtrk8.9 (5.7)7.2 (4.8)5.2 (2.4)7.5 (5.7)

12 EGU Vienna, April DTU Space, Technical University of Denmark Coastal regions heavily improved DTU 2012 Beta Including CRYOSAT LRM data - 30% more data. Currently investigating ESA L2 LRM vs NOAA LRM data. Including Retracked L1 CRYOSAT SAR and SAR-In data Has to solve for ”mode jumps first” Updating all existing GM data. Ocean tide correction updated to GOT 4.7 SSB correction updated (N/A for Cryosat-2) Dynamic Atmosphere updated from IB alone StandardsDNSC08/DTU10DTU12 Beta Dry troposphereECMWF Wet troposphereECMWFRadiometer IonosphereAltimeter Dynamic AtmosphereIB (1013 mbar)MOG-2D_IB Ocean tidesGOT 00.2GOT4.7 Sea State BiasBM4Non-PARAM

13 EGU Vienna, April DTU Space, Technical University of Denmark Retracking of Cryosat-2 Level 1b SAR waveform (black) with fitted five parameter beta retracker with exponential tail (blue) and surface estimate (red). Level 1b SAR waveform (black) with fitted five parameter beta retracker with exponential tail (blue) and surface estimate (red). Green is cut off for leading edge Center of Gravity COG – Center of Gravity

14 EGU Vienna, April DTU Space, Technical University of Denmark DTU12? Gravity

15 EGU Vienna, April DTU Space, Technical University of Denmark Coastal regions heavily improved All > obsDTU12DTU10SAND 18EGM2008 Purple (0-20 m DEPTH) Dark Blue (20-50 m) Light Blue ( m) Green ( m) Yellow ( m) Red/Pink (>1000 m) All DTU 2012 Beta Preliminary testing using 1.6 years of NOAA C2 LRM Data

16 EGU Vienna, April DTU Space, Technical University of Denmark Summary ESA L2 LRM are very good for marine gravity Processor upg ( ) removes spikes and is better for SAR-In But increases noise for LRM Jumps between modes are clear and needs to be handled Current Cryosat 2 data are comparable to retracked GM altimetry Aims at releasing DTU12 at “20 years progress of altimetry” Jason-1 EOL Geodetic Mission ?. Will still be a fantastic asset for marine gravity up to the 66 parallel (no Arctic here).


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