Trends in the Vertical Distribution of Ozone

Analyses of satellite, ground-based, and balloon measurements allow updated estimates of trends in the vertical profile of ozone since 1979. The results show overall consistency among several independent measurement systems, particularly for northern hemisphere midlatitudes where most balloon and ground-based measurements are made. Combined trend estimates over these latitudes for the period 1979-96 show statistically significant negative trends at all altitudes between 10 and 45 km, with two local extremes: -7.4 plus or minus 2.0% per decade at 40 km and -7.3 plus or minus -4.6% per decade at 15 km altitude. There is a strong seasonal variation in trends over northern midlatitudes in the attitude range of 10 to 18 km, with the largest ozone loss during winter and spring. The profile trends are in quantitative agreement with independently measured trends in column ozone, the amount of ozone in a column above the surface. The vertical profiles of ozone trends provide a fingerprint for the mechanisms of ozone depletion over the last two decades.