Journal of Oceanography, Vol. 64 (No. 6), pp. 831-845, 2008
Fabien Durand1,2*, Doraiswamy Shankar2, Florence Birol3 and S. Satheesh Chandra Shenoi2
1IRD, LEGOS, UMR5566 CNRS-CNES-IRD-UPS, 14 Avenue Edouard Belin, 31400 Toulouse, France
2Physical Oceanography Division, National Institute of Oceanography, Dona Paula, Goa 403004, India
3Center for Topography of Oceans and Hydrosphere, LEGOS, UMR5566 CNRS-CNES-IRD-UPS, 14 Avenue Edouard Belin, 31400 Toulouse, France
(Received 20 July 2007; in revised form 28 April 2008; accepted 28 April 2008)
Abstract: We present a methodology to derive surface geostrophic current from a newly released altimetric sea-level data set. TOPEX/Poseidon data were first completely reprocessed from Geophysical Data Records using new algorithms accommodating marginal seas and coastal conditions. The methodology applied to the reprocessed data essentially consists of a smoothing of the raw along-track coastal altimetric data at scales at which the geostrophic equilibrium holds. This was reduced to a computational procedure using a set of objective criteria. We have applied the method to the East India Coastal Current (EICC) at the western boundary of the Bay of Bengal. This paper first examines the quality of the new data set, which compares well with tide-gauge data; the current we derived is consistent with independent estimates. Our methodology reveals the full spectrum of the along-shore current, ranging from intra-seasonal to inter-annual time scales, from the deep ocean to the shelf-break area where the EICC exists. The algorithm can be applied to any coastal region where an order of the Rossby radius can be defined, and it therefore opens up bright prospects for mapping the variability of other boundary-current systems in the world ocean from altimetry.