Empirical nonlinear determination of the diffuse attenuation coefficient Kd(490) in coastal waters from ocean color images

The fine-scale study of the diffuse attenuation coefficient, K d (O ), of the spectral solar downward irradiance is only feasible by ocean color remote sensing. Several empirical and semi-analytical methods exist. However, most of tthese models are generally applicable for clear open ocean waters . They show limitations when applied to coastal waters. A new empirical method based on neural networks has been developed using a relationship between the remote-sensing reflectances between 412 and 670 nm and K d (490), for the SeaWiFS ocean color re mote sensor. The architecture of the neural network has been defined using synthetical and in situ dataset and the optimal design is a tow hidden layer neural network with 4 neurons of the first layer and three on the second layer. The comparis on with the SeaWiFS empirical algorithms shows similar retrievals accuracies for low values of K d (490) (i.e.