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AN ANALYSIS OF THERMAL AVHRR IMAGES OF COLD EDDIES IN THE 
CABO FRIO REGION (RJ) 
C.L. Silva Jr., J. A. Lorenzzetti, S. Maluf, J.L. Stech e C.E.S. Araujo 
Divisäo de Sensoriamento Remoto (DSM) 
Instituto Nacional de Pesquisas Espaciais (INPE) 
Commission VII, Working Group 8 
KEYWORDS: Oceanic Eddies, AVHRR Images, Oceanography from Space, Brazil Current, 
Upwelling, SST 
ABSTRACT 
A set of AVHRR data (5 channels) were processed for the generation of atmospherically 
corrected SST (Sea Surface Temperature) images. A total of 10 images of the winter seasons 
(June/July) of 1992 and 1993 were geometrically corrected and changed to the same scale and 
projection (Mercator). A linear stretching algorithm was also applied to all SST images in 
order to enhance the oceanographic features present. Use of sequences of images made it 
possible to analyse the formation and the movement of cold eddies present in these images. 
Two characteristic sizes of cold eddies were noticed: the larger ones having a diameter of 100 
km, and the smaller ones with a diameter of 50 km. The images analyzed suggests that larger 
cold eddies are formed by an amplification of the meandering of the west wall of Brazil 
Current after it passes Cabo Frio making a cyclonic turning and trapping cold upwelled water 
present over the shelf. The smaller eddies seem to be formed by an eastward propagation of 
cold pools of upwelled water near the coast. These cells of cold water are then found near west 
all of the Brazil Current, being advected to SW. The typical advection velocities of such 
features were 18 cm.s *, ranging in the analysed data set from 7 cm.s ! to 30 cm.s .. 
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