THE EULER VECTOR - A POLARIMETRIC DESCRIPTOR OF THE OCEAN SURFACE

The mean polarimetric behavior of the sea surface, on a time-averaged measurement, can be described by its averaged Mueller matrix. A method for the calculation of this matrix has already been proposed: it cons ists of an extension of the small perturbations technique to the vecto rial case, from a two-scale sea surface model. In this article a backs cattering model is shown, which is representative of a single instanta neous measurement instead of a time-average of measurements. For this purpose, the polarimetric response is characterized by the sea surface ''polarization fork,'' described by the five Euler parameters. A mini mal polarimetric descriptor is defined, the Euler vector, characterizi ng a ''frozen'' sea state, and whose components are the averaged value s of the Euler parameters. The main interest of such a polarimetric si gnature of the sea surface is that the component of this new descripto r can be linked with the observation parameters (incidence of the illu mination, azimuthal direction of the observation with respect to the w ind direction, speed of the wind), in other words with the physical ch aracteristics of the ocean surface.