Advective Surface Velocities Derived from Sequential Infrared Images in the Southwestern Atlantic Ocean

Abstract

Sequential infrared satellitebeen usedbetween November images 1995 and August 1996 have to derive sea sur- face advective velocities in the southwestern Atlantic Ocean using the Maximum Cross-Correlation (MCC) technique. The infrared images, geometrically corrected and accurately registered to a map grid, are masked for land and cloud cover. The linear displacements of the sea surface thermal features are determined by locating the maximum cross-correlation in windowed portions of suc- cessive images. The advective velocities are estimated for each pair of images based on regular grids. Incoherent vectors are eliminated from these fields using a statistical method. After this, a visual inspection by the operator is completed to remove the remaining fictitious vectors. The region studied includes the southern Brazilian, Uru- guayan, and northern Argentinian shelves and the neigh- boring oceanic area known as the Brazil-Malvinas Con- fluence. Despite the rather complex circulation of this region, the advective surface currents calculated by the MCC method are consistent with the shapes of the sea surface temperature features. The general patterns of the surface circulation estimated by the MCC agree well with previous studies that used direct measurements, hydro- graphic data, and/or modeling efforts. In the shallower areas of the study region, the MCC technique is less ap- plicable due to the predominance, in violation of the as- sumptions of the method, of nonadvective processes.