The problem of calculation of brightness coefficient of the solar light reflected by the atmosphere in regions with spatially-local horizontal inhomogeneities (surface of medium discontinuity) is considered in case when usual one-dimensional one-layer model is not applicable. Two-dimensional model allowing a detailed spatial distribution of brightness coefficient in the vicinity of the inhomogeneity is suggested. Typical distributions are obtained via this model. Quasi-one-dimensional model is suggested for operative estimation of a subregion size, where multi-dimensional effects in brightness are essential. Numerical testing of this model is carried out.
boundary effects; cloud; mathematical model