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

Abstract

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 Niño–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.