Upper Tropospheric Tropical Ozone Variations and Trends: Satellite and Model Results

There are large uncertainties and variability in tropospheric ozone (O3) trends. We investigate ozone variations in the upper troposphere (UT) based on 14 years of high quality daily measurements by the Microwave Limb Sounder (MLS) aboard the Aura satellite, launched in 2004. More specifically, we compare spatio-temporal variations and trends in tropical UT O3 from MLS to model results from the Whole Atmosphere Community Climate Model (WACCM). We apply the same multiple linear regression to monthly mean time series of observed and modeled upper tropospheric ozone abundances, binned in latitude/longitude. We present the resulting large-scale regional O3 trends and related spatial patterns, as well as correlations between the observed and modeled UT O3 time series. Lower stratospheric ozone trends are also briefly covered. We discuss our results in the context of other recent work on upper tropospheric and lower stratospheric (UTLS) ozone.