To help understand the role of ozone in protecting life on earth, a br
ief review is presented of the processes which determine the 'normal'
distribution of ozone in the stratosphere and its variations with lati
tude, with elevation and with time of year, Next, the absorption of UV
radiation by ozone is discussed, including the dependence of the surf
ace exposure to UV radiation on solar elevation, ozone amount and clou
d amount.