Atmospheric correction for the satellite visible data over heterogeneous surfaces

摘要

An atmospheric correction algorithm over the heterogeneous surface on the emergent radiation from the top of the atmosphere is proposed. The surface is simulated by checkerboard type terrain composed of land or ocean pixels. The look-up-table method is used for the atmospheric correction. To investigate the contribution of adjacent pixels, two additional parameters based on the diffuse transmission and reflection function of the atmosphere are introduced. These parameters are independent of the surface reflection properties. At present, the ocean surface is in accordance with the Cox and Munk model surface, whereas that of land is assumed to be Lambertian. The upwelling radiation emerging from the top of the atmosphere is expressed by a sum of radiative interactions between the surface and the atmosphere, and it is simulated using these parameters and combinations until convergence. The present method was developed with reference to currently existing numerical results based on the one-dimensional radiative transfer code.An example of numerical simulation is shown at a wavelength of 0.56 μm, which corresponds to the representative wavelength of the visible region of spectrum. The dust-like model is used for the aerosols, and the land surface albedo is 0.2 or 0.4. The isotropic ocean wind is 5m/s, and the refractive index is 1.333. The effect of the land surface on the radiance over the ocean is stronger just off the coastal zone and decreases exponentially with increasing distance from the land. It depends upon the solar zenith angle and atmospheric condition as well. The present new version enables us to quantitatively discuss radiative transfer over the heterogeneous surface including the coastal zone. A typical numerical simulation is performed over the Tsukuba lake area in Japan.