Seasonal characteristics of hydrography, turbulence and dispersion near Ilha Grande (RJ), Brazil, based on R/V "Prof. W. Besnard" data

Abstract

Seasonal differences in sigma-t (1.8), temperature (4.0 0 C) and salinity (0.9% 0) were observed during February/June 1976 in the vicinity of Ilha Grande off the coast of Brazi~. Estimates of static and dynamic stability were made through the calcu-Zation of Brunt-Vàisala frequencies and Richardson numbers, respectively. Both static and dynamic stability values were larger in February than in June for the same location and suggest a greater column stability in February than in June. Stations located in the northern and western channels of Ilha Grande, however, contained greater density reversals than to the east of the Island. SrraU scale dispersion studies were made using Rhomamine B dye to determine horizontal diffusion coefficients (K) east of the IsZand and in an embayment of the Island. The estimate for K was 9X10 3 cm 2 S-l east of the Island, about 2.6 times greater than the value estirrated for the protected embayment.