Ozone depletion in the high latitude lower stratosphere: 1979–1990

Abstract

Archived Stratospheric Aerosol and Gas Experiment (SAGE, SAGE II) and Solar and Backscattered Ultraviolet (SBUV) data are used to examine lower stratospheric O 3 variations at 50° latitude in both hemispheres. These data indicate that from 1979 to 1985, 73–90% of the total O 3 changes have occurred below approximately 25 km in altitude. Significant O 3 depletions (up to 15%) have occurred in the partial column (127–15.8 mbar) in both hemispheres with indications of a recovery after 1985. Both the SAGE/SAGE II and SBUV observations show essentially the same changes for this partial column. Below 20 km and between 1979 and 1985, larger local O 3 depletions are suggested by the SAGE/SAGE II data sets. Temporally, the largest 365‐day running mean O 3 changes occur in 1982–1983 in the northern hemisphere and in late 1984 and early 1985 in both hemispheres. Possible explanations are discussed. Two‐dimensional model simulations of O 3 changes from 1979 to 1990 have been carried out. Comparisons with O 3 data are presented. Model results suggest that by 1985, significant declines in global O 3 were caused by destruction by odd nitrogen associated with long‐term variations in the flux of precipitating relativistic electrons (2.6%); solar UV flux changes (1.8%); the dilution effect associated with the Antarctic O 3 hole (1.2%); and atmospheric increases in CH 4 , N 2 O, and chlorofluorocarbons (0.4%). Analyses of drift‐corrected SBUV and Total Ozone Mapping Spectrometer (TOMS) data and model calculations indicate that between 1979 and 1985, reductions of 4.3 to 4.8% in total column O 3 averaged between 65°S and 65°N have occurred. Calculations indicate a full global O 3 decline of 5.2% (peak‐to‐peak) or 6% (annual average) between 1979 and 1985 with a partial recovery between 1985 and 1989.