d.i. lysaker, o.c.d. omang , d. solheim esa living planet symposium, bergen 30. june 2010
DESCRIPTION
D.I. Lysaker, O.C.D. Omang , D. Solheim ESA Living Planet Symposium, Bergen 30. June 2010. Geostrophic Surface Currents in the Northern North Atlantic revealed by GOCE, Gravity Anomalies and MSSH. This presentation shows an example of how to use geodetic data in climate studies. - PowerPoint PPT PresentationTRANSCRIPT
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Geostrophic Surface Currents in the Northern North Atlantic revealed by GOCE, Gravity Anomalies and MSSH
D.I. Lysaker, O.C.D. Omang, D. Solheim
ESA Living Planet Symposium, Bergen 30. June 2010
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This presentation shows an example of how to use geodetic data in climate studies
Gravity + MSSH
Geostrophic ocean
surface currents
Direct
Synthetic
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Ocean circulation may be estimated if height above geoid is known
Ocean Circulation and Transport between the North Atlantic and the Arctic Sea
www.science.nasa.gov
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OCTAS -Ocean Circulation and Transport between the North Atlantic and the Arctic Sea
Courtesy Kourosh Ghazavi
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Oceanographic models
• Salinity• Temperature
OCCAM
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Two methods for estimating geostrophic surface currents
• Direct– MDT obtained using LSC
– Combine MSSH and gravity data
• Synthetic– MDT derived by subtracting a regional
gravimetric geoid from a MSSH model
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Direct method uses LSCCross-covariance
between observations y and signal x
Error covariances
Auto-covariance of observations
a-priori signal variance matrix
Covariance matrix for the measurement noise
MDT
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Synthetic method
MDT = MSSH – N + e
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Data used in the direct and synthetic method
MSSH (OCTAS06v3/DNSC08)
Gravity data
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Gravity coverage is not complete in our test area … fill with gravity data from altimetry
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Both models give a lot of features
Combined model (MSSH and g)
Direct model(MSSH and N)
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Geodetic model has smaller features than oceanographic model
Geodetic model (MSSH-N)Oceanographic model (OCCAM)
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Synthetic model fits drifter data better
Average: 10.5 cm/s
Standard deviation: 9.3 cm/s
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Combination model and drifter data
Average: 11.2 cm/s
Standard deviation: 9.8 cm/s
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OCCAM fits better with drifter data
Model Mean Stdsubtracted (cm/s) (cm/s)
MDT_octas06 11.1 9.8
MDT_dnsc08 11.2 9.8
SMDT_octas06 11.3 16.9
SMDT_dnsc08 10.5 9.3
OCCAM 8.5 8.0
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Mooring data
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Drifter data fits as good/bad with mooring data as combination model
Model Mean Stdsubtracted (cm/s) (cm/s)
MDT_octas06 8,6 5,3
MDT_kms04 7,7 5,5
MDT_dnsc08 5,4 2,7
SMDT_octas06 10,1 5,2
SMDT_kms04 14,4 8
OCCAM 7,3 4,4
drifter 7,9 6,7
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• Using geodetic data reveals smaller features than oceanographic models
• Redistribution of water is due to change in climate
– Gravity observations may contribute to monitor this change
Conclusions