OZONE DEPLETION AT MIDLATITUDES - COUPLING OF VOLCANIC AEROSOLS AND TEMPERATURE VARIABILITY TO ANTHROPOGENIC CHLORINE

Satellite observations of total ozone at 40-60 degrees N are presented from a variety of instruments over the time period 1979-1997. These r eveal record low values in 1992-3 (after Pinatubo) followed by partial but incomplete recovery. The largest post-Pinatubo reductions and lon ger-term trends occur in spring, providing a critical test for chemica l theories of ozone depletion. The observations are shown to be consis tent with current understanding of the chemistry of ozone depletion wh en changes in reactive chlorine and stratospheric aerosol abundances a re considered along with estimates of wave-driven fluctuations in stra tospheric temperatures derived from global temperature analyses. Tempe rature fluctuations are shown to make significant contributions to mod el calculated northern mid-latitude ozone depletion due to heterogeneo us chlorine activation on liquid sulfate aerosols at temperatures near 200-210K (depending upon water vapor pressure), particularly after ma jor volcanic eruptions. Future mid-latitude ozone recovery will hence depend not only on chlorine recovery but also on temperature trends an d/or variability, volcanic activity, and any trends in stratospheric s ulfate aerosol.