Effect of the observation length on the two-dimensional shadowing functionof the sea surface: application on infrared 3-13-mu m emissivity

An analytical approach of the two-dimensional emissivity of a rough sea sur face in the infrared band is presented. The emissivity characterizes the in trinsic radiation of the sea surface. Because the temperature measured by t he infrared camera depends on the emissivity, the emissivity is a relevant parameter for retrieving the sea-surface temperature from remotely sensed r adiometric measurements, such as from satellites. This theory is developed from the first-order geometrical-optics approximation and is based on recen t research. The typical approach assumes that the slope in the upwind direc tion is greater than the slope in the crosswind direction, involving the us e of a one-dimensional shadowing function with the observed surface assumed to be infinite. We introduce the two-dimensional shadowing function and th e surface observation length parameters that are included in the modeling o f the two-dimensional emissivity. (C) 2000 Optical Society of America. OCIS codes: 010.4450, 030.6600, 080.2720, 000.5490.