ATMOSPHERIC CORRECTION OVER CASE-2 WATERS WITH AN ITERATIVE FITTING ALGORITHM - RELATIVE-HUMIDITY EFFECTS

In algorithms for the atmospheric correction of visible and near-IR sa tellite observations of the Earth's surface, it is generally assumed t hat the spectral variation of aerosol optical depth is characterized b y an Angstrom power law or similar dependence. In an iterative fitting algorithm for atmospheric correction of ocean color imagery over case 2 waters, this assumption leads to an inability to retrieve the aeros ol type and to the attribution to aerosol spectral variations of spect ral effects actually caused by the water contents. An improvement to t his algorithm is described in which the spectral variation of optical depth is calculated as a function of aerosol type and relative humidit y, and an attempt is made to retrieve the relative humidity in additio n to aerosol type. The aerosol is treated as a mixture of aerosol comp onents (e.g., soot), rather than of aerosol types (e.g., urban). We de monstrate the improvement over the previous method by using simulated case 1 and case 2 sea-viewing wide field-of-view sensor data, although the retrieval of relative humidity was not successful. (C) 1997 Optic al Society of America.