Aerosol Analysis with the Coastal Zone Color Scanner: A Simple Method for Including Multiple Scattering Effects

For measurement of aerosols over the ocean, the total radiance L _t backscattered from the top of a stratified atmosphere which contains both stratospheric and tropospheric aerosols of various types has been computed. A similar computation is carried out for an aerosol-free atmosphere yielding the Rayleigh scattered radiance L _r . The difference L _t − L _r is shown to be linearly related to the radiance L _as , which the aerosol would produce in the single scattering approximation. This greatly simplifies the application of aerosol models to aerosol analysis by satellite since adding to, or in some way changing, the aerosol model requires no additional multiple scattering computations. In fact, the only multiple computations required for aerosol analysis are those for determining L _r , which can be performed once and for all. The computations are explicitly applied to Band 4 of the CZCS, which, because of its high radiometric sensitivity and excellent calibration, is ideal for studying aerosols over the ocean. Specifically, the constant A in the relationship L _as = A ⁻¹ ( L _t − L _r ) is given as a function of position along the scan for four typical orbital–solar position scenarios. The computations show that L _as can be retrieved from L _t − L _r with an average error of no more than 5–7% except at the very edges of the scan.