EFFECTS OF STRATOSPHERIC OZONE DEPLETION AND TROPOSPHERIC POLLUTION ON UVB RADIATION IN THE TROPOSPHERE

摘要

A radiative transfer model is used to study the effect of stratospheric ozone depletion and tropospheric pollution on UVB (280-315 nm) radiation in the troposphere at midlatitudes of the Northern Hemisphere. The difference in the vertical distribution of UVB radiation for a range of pollution conditions typical for remote clean and more polluted sites on cloudless summer days is shown. The changes in downward UVB irradiance, WE actinic flux, DNA-weighted UV radiation and photodissociation frequency of ozone at the earth's surface are quantified in relation to stratospheric ozone depletion and typical ranges of tropospheric: pollutants (ozone [O-3], sulfur dioxide [SO2] and aerosols) in nonurban polluted regions. The results show that near the earth's surface, in nonurban polluted regions, an increase of tropospheric pollution, which occurred over the last 50-100 years, has cancelled the effect of an increase of UVB radiation due to stratospheric ozone depletion that has occurred since the late 1970s. The results hold for summer conditions and the decrease of UVB radiation is most pronounced in the polluted boundary layer. At higher altitudes the effect of tropospheric pollution on UVB radiation is far less, Prior to 1970 it was mainly tropospheric pollution that altered UVB radiation at the surface of the earth. In addition, since the late 1970s enhanced UVB radiation reaching the tap of the troposphere, due to stratospheric ozone depletion, also had an impact on WE levels in the troposphere. [References: 63]