Variations in tropical total ozone as measured by TOMS

Abstract

The Total Ozone Mapping Spectrometer (TOMS) instrument on Nimbus 7 has been measuring the total column amount of ozone over the globe for more than 11 years. Recent improvements in the data analysis have led to a technique for determining drift in the calibration to nearly one percent over this time period. The TOMS calibration is now determined well enough to act as an absolute measure of ozone change. TOMS tropical data shows the clear signal of the quasi-biennial oscillation which is mixed with a seasonal signal of about the same magnitude. The data show a slight downward trend of less than 1% per decade, which is not statistically significant, for the 11 1/2 year period.