On the disproportionate role of tropospheric ozone as a filter against solar UV‐B radiation

Abstract

Increases in tropospheric ozone due to photochemical production, mostly due to growing industrial and technological NOx‐ emissions, in the industrialized northern hemisphere can overcompensate for increased UV‐B radiation resulting from ozone depletions due to chlorine‐catalyzed reactions in the stratosphere. This is especially the case in the summer months, because during this period a large fraction of the UV, which reaches the surface as diffuse radiation, is scattered by air molecules, droplets and aerosol particles in the troposphere. This causes a relatively longer path through tropospheric than through stratospheric ozone. Analyses using calculated, as well as observed ozone profiles at the station Hohenpeißenberg in Bavaria, FRG, show, that decreases of UV‐B radiation at the earth's surface are possible even when total ozone declines.