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The Determination of the Large-Scale Circulation of the Pacific Ocean from Satellite Altimetry using Model Green's FunctionsA Green's function method for obtaining an estimate of the ocean circulation using both a general circulation model and altimetric data is demonstrated. The fundamental assumption is that the model is so accurate that the differences between the observations and the model-estimated fields obey a linear dynamics. In the present case, the calculations are demonstrated for model/data differences occurring on very a large scale, where the linearization hypothesis appears to be a good one. A semi-automatic linearization of the Bryan/Cox general circulation model is effected by calculating the model response to a series of isolated (in both space and time) geostrophically balanced vortices. These resulting impulse responses or 'Green's functions' then provide the kernels for a linear inverse problem. The method is first demonstrated with a set of 'twin experiments' and then with real data spanning the entire model domain and a year of TOPEX/POSEIDON observations. Our present focus is on the estimate of the time-mean and annual cycle of the model. Residuals of the inversion/assimilation are largest in the western tropical Pacific, and are believed to reflect primarily geoid error. Vertical resolution diminishes with depth with 1 year of data. The model mean is modified such that the subtropical gyre is weakened by about 1 cm/s and the center of the gyre shifted southward by about 10 deg. Corrections to the flow field at the annual cycle suggest that the dynamical response is weak except in the tropics, where the estimated seasonal cycle of the low-latitude current system is of the order of 2 cm/s. The underestimation of observed fluctuations can be related to the inversion on the coarse spatial grid, which does not permit full resolution of the tropical physics. The methodology is easily extended to higher resolution, to use of spatially correlated errors, and to other data types.
Document ID
19970032012
Acquisition Source
Jet Propulsion Laboratory
Document Type
Reprint (Version printed in journal)
External Source(s)
Authors
Stammer, Detlef
(Massachusetts Inst. of Tech. Cambridge, MA United States)
Wunsch, Carl
(Massachusetts Inst. of Tech. Cambridge, MA United States)
Date Acquired
September 6, 2013
Publication Date
August 15, 1996
Publication Information
Publication: Journal of Geophysical Research
Publisher: American Geophysical Union
Volume: 101
Issue: C8
ISSN: 0148-0227
Subject Category
Oceanography
Report/Patent Number
Paper-96JC01150
NASA-CR-205310
NAS 1.26:205310
Accession Number
97N29070
Funding Number(s)
CONTRACT_GRANT: JPL-958125
CONTRACT_GRANT: NSF OCE-92-05942
CONTRACT_GRANT: NAGw-1048
Distribution Limits
Public
Copyright
Public Use Permitted.
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