The vertical distribution of ozone at Pretoria from July 1990 to June 1991 and its changes

Total ozone and the vertical distribution of ozone were measured at Pretoria between 1965 and 1968. Total ozone measurements recommenced in Pretoria in August 1989, and measurements of the vertical distribution of ozone near Pretoria recommenced in July 1990. Relative to the earlier data, mean monthly total ozone values are significantly higher in all months, with a mean annual relative increase of 12 percent. The recent profiles show a significant increase in the mean monthly concentration of ozone in the lowest 12 km. Concurrent to this increase a relative decrease in ozone concentration is shown between 12 and 42 km. The increased ozone concentration in the lower troposphere may be related to urbanization and the increase in ozone-forming nitrogen oxides over the last two decades. It is suggested that the decreased ozone concentration in the stratosphere and upper troposphere is evidence of the global decrease in the mid-latitudes of the Southern Hemisphere.