FUNCTION OF STRATOSPHERIC AEROSOL IN TRAN SFORMATION OF ULTRAVIOLET-RADIATION FLOW AT LOW SUN

Spectral and integral peculiarities of intensification of the solar UV radiation at the Earth's surface at large solar zenith angles (''twil ight effect'' (TE)) are calculated. The duplication method was used in the plane-parallel approximation, the strongly absorbing atmosphere w ith a scattering layer being considered. The results of calculations s ignificantly improve the previous estimations of this important effect , since the method takes into account the molecular scattering and the level of the aerosol layer location. The influence of distribution of ozone with height on TE is picked out. The spectral distributions of TE are analyzed, the maximum of TE being obtained at 300-315 nm, i.e., in the range known as ''window of transparency'' of ozone.