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Annales Geophysicae An interactive open-access journal of the European Geosciences Union
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Volume 16, issue 5
Ann. Geophys., 16, 638–650, 1998
https://doi.org/10.1007/s00585-998-0638-0
© European Geosciences Union 1998
Ann. Geophys., 16, 638–650, 1998
https://doi.org/10.1007/s00585-998-0638-0
© European Geosciences Union 1998

  31 May 1998

31 May 1998

Combining T/P altimetric data with hydrographic data to estimate the mean dynamic topography of the North Atlantic and improve the geoid

P. LeGrand1, H. Mercier1, and T. Reynaud2,1 P. LeGrand et al.
  • 1Laboratoire de Physique des Océans, Unité mixte CNRS-IFREMER-Université de Bretagne Occidentale, IFREMER centre de Brest, B.P. 70, F-29280 Plouzané , France
  • 2Now at LEG1/MEOM, Institut de Mécanique de Grenoble, B.P. 53, F-38041 Grenoble CEDEX, France

Abstract. The mean dynamic topography of the surface of the North Atlantic is estimated using an inverse model of the ocean circulation constrained by hydrographic and altimetric observations. In the North Atlantic, altimetric observations have no significant impact on the topography estimate because of the limited precision of available geoid height models. They have a significant impact, however, when uncertainties in the density field are increased to simulate interpolation errors in regions where hydrographic data are scarce. This result, which moderates the conclusion drawn by Ganachaud and co-workers of no significant contribution of altimetric observations to the determination of the large-scale steady circulation, reflects the simple idea that altimetric data are most useful near the surface of the ocean and in areas where the hydrography is poorly determined. One application of the present inverse estimate of the mean dynamic topography is to compute a geoid height correction over the North Atlantic which reduces the uncertainty in the geoid height expanded to spherical harmonic 40 down to a level of about 5 cm.

Key words. Oceanography: general (climate and interannual variability) · Oceanography: physical (general circulation; remote sensing)

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