An Update through 1985 of the Variations in Global Total Ozone and North Temperate Layer-Mean Ozone

Abstract

Total-ozone variations in five climatic zones and the world as a whole, as well as ozone variations in tropospheric and stratospheric layers of the north temperate zone, have been updated through 1985 by means of Dobson, ozonesonde and Umkehr observations. In the north temperate zone the total-ozone minimum in early 1985 was as pronounced as the total-ozone minimum in early 1983 (both a record 3% below the long-term average), but without the potential explanation afforded by the El Chichón eruption and/or strong El Niño of 1982. Based on linear regression, between 1980 and 1985 the year-average total ozone decreased by 2?3% in north polar, north and south temperate, and tropical zones, but by almost 6% in the south polar zone (Antarctic ?ozone hole? phenomenon). For the world as a whole, the decrease in year-average total ozone between 1980 and 1985 is estimated to be 2.7 ± 0.9% (95% confidence interval), with the decrease greatest in the northern autumn (3.3%) and winter (3.1%) and least in the northern summer (1.6%). Ozonesonde and Umkehr observations for 16?24 and 24?32 km layers of the north temperate zone also show record low (since 1970) ozone values in both 1983 and 1985. Based on linear regression, between 1980 and 1985 the year-average ozone in the north temperate zone decreased by about 6% in the 16?24 km layer, nearly 2% in the 24?32 km layer, and nearly 6% in the 32?48 km layer, though the latter decrease is presumably exaggerated because of the bias introduced into the Umkehr measurements by the El Chichón eruption in 1982. There is little evidence of appreciable changes in tropospheric ozone during 1980?85.