Wednesday, 12 February 2003
Sverdrup transport calculation using Satellite scatterometer wind products in the North Pacific
Satellite scatterometer data (ERS-1/2, NSCAT, QSCAT) are used to construct gridded products of surface wind/wind-stress vectors over the Pacific and Indian Oceans. In the tropical Pacific region, these products have a good relationship with TAO buoy data, meaning sufficiently reliability. However, in the mid- and high-latitude regions, it is difficult to clarify the reliability of these gridded data products, because there are few in-situ measurement data in such regions except near-shore areas. Instead, we make inter-comparisons with objectively analyzed wind products (ECMWF and NCEP). In the averaged (1992-1999) wind-stress and wind-stress curl fields, significant differences are recognized among these product with maximum difference of about 0.02 N m-2 around 45N and about 7 x 10-8 N m-3 around 30N. Based on the Sverdrup theory, we calculate zonally-integrated Sverdrup transport in the zonal band between 20N and 30N from the respective wind products, and compare them with each other. The integrated Sverdrup transport along 27.5N calculated from the ERS product (30Sv) is smaller than one from the NCEP's(40Sv) and larger than the ECMWF's(25Sv). This suggests that estimation of the wind-driven oceanic transport is highly sensitive to selected wind products. The Sverdrup transport minus meridional Ekman transport, namely meridional geostrophic transport are estimated by these wind product, and compared with the zonal gradient of the dynamic height field calculated from historical hydrographic data (WOA98) in these zonal bands.
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