TROPHOSPHERIC OZONE TRENDS OVER CANADA - 1980-1993

An analysis of ozone in the troposphere at five sites in Canada is pre sented, using ECC sonde data from 1980-1993. The entire data record ha s been carefully reexamined for quality, and where necessary reevaluat ed from the raw telemetry. Trend analysis is performed on both the raw and the corrected (normalized to the total ozone measurement) profile s. The correction factors are also examined for trends. Where required , the data are adjusted for diurnal variation introduced by changes in time of launch. We find statistically significant (2sigma) decreases in concentration at all stations except Alert, and in most cases, at a ll levels, including the surface. The tropospheric trends we derive he re are compared with corresponding lower stratospheric trends. Althoug h the long-term trends are similar, stratospheric variations on shorte r time scales are not well-correlated with those in the troposphere.