Interannual variability and trends in tropical ozone derived from SAGE II satellite data and SHADOZ ozonesondes

Long-term observations of stratospheric ozone from the Stratospheric Aerosol and Gas Experiment II (SAGE II) satellite (1984-2005) are combined with ozonesonde measurements from the Southern Hemisphere Additional Ozonesondes (SHADOZ) network (1998-2009) to study interannual variability and trends in tropical ozone. Excellent agreement is found comparing the two data sets for the overlap period 1998-2005, and the data are combined to form a continuous time series covering 1984-2009. SHADOZ measurements also provide temperature profiles, and interannual changes in ozone and temperature are highly correlated throughout the tropical lower stratosphere (16-27 km). Interannual variability in stratospheric ozone is dominated by effects of the quasi-biennial oscillation and El Nio-Southern Oscillation, and there are also significant negative trends (-2 to -4% per decade) in the tropical lower stratosphere (over 17-21 km). These tropical ozone trends are consistent with results from chemistry-climate model simulations, wherein the trends result from increases in upwelling circulation in the tropical lower stratosphere.