Diffusion Coefficients for Coastal Water Determined from Aerial Photographs

摘要

The horizontal coefficient of mixing (diffusion coefficient) in the ocean is necessary for a large variety of coastal and marine environmental studies. Two coastal embayments along the southeastern coast of Brazil were studied. Rhodamine-B dye was dissolved in methanol and the solution was separated into three aliquots, each containing about 100 gm. of dye. During the experiment, an aircraft flew over the area and took a number of photographs with an RC-10 metric camera. From the film images it was possible to extract information on the areal changes of each dye patch. The data were used to construct dispersion diagrams. Using a least squares method, the diffusion coefficients for three dispersals were determined. The largest value corresponded to a bay more exposed to the sea, than the other two locations. The values, derived from aerial photographs, compared very well with previous determinations of K, based on conventional fluorometric methodology in a nearby area. It is suggested that it is possible to obtain reasonable estimates of diffusion from aerial photographs.