Adjacency effects on water surfaces: primary scattering approximation and sensitivity study

The making of atmospheric corrections is a critical task in the interpretat ion of ocean color imagery. In coastal areas, a fraction of the light refle cted by the land reaches a sensor. Modeling the reduction of image contrast when the atmospheric turbidity increases, the so-called adjacency effect, requires large amounts of computing time. To model this effect we developed a simple approach based on the primary scattering approximation for both n adir and off-nadir views. A sensitivity study indicates that the decisive c riterion for measurement accuracy for aerosols is their vertical distributi on. As this distribution cannot generally be determined from space, it is n ot possible to include a suitable correction of the adjacency effects on sa tellite imagery. Conversely, we propose a simple correction for molecular s cattering based on the isotropic approximation. We also address the problem of reduction of the coupling between the Fresnel reflection and the atmosp here for observations of coastal water. We study the influence of the adjac ency effects on determination of the abundance of chlorophyll in water by c ombining use of the red and the infrared bands for aerosol remote sensing a nd the blue/green-ratio technique for retrieval of these data. (C) 2000 Opt ical Society of America OCIS codes: 010.0010, 010.1310, 010.4450.