INCREASED TRANSMISSION OF ULTRAVIOLET-RADIATION TO THE SURFACE DUE TO STRATOSPHERIC SCATTERING

The relative enhancement of ultraviolet radiation reaching the surface due to scattering by stratospheric aerosols is shown to be consistent with single-scattering theory, rather than the photon-trapping effect described by some recent studies. The enhancement is greatest for large solar zenith angles when there is a significant absorbing layer below the stratospheric aerosol. Under appropriate conditions of ozone depletion and the presence of volcanic aerosol this enhancement makes it possible for the UV flux reaching the surface at high southern latitudes to exceed the peak flux at the equator, but only for wavelengths shorter than about 290 nm.