Factors Affecting Global Tropospheric Ozone: Constraining Recent Model Developments with Observations from Ozonesonde, Aircraft, and Satellite

Here we use the GEOS-Chem chemical transport model as a platform to test our current knowledge of key factors controlling tropospheric ozone. We provide a comprehensive evaluation of the most recent version of GEOS-Chem model for global tropospheric ozone with an ensemble of observations, including 1) the worldwide ozonesonde observations from WOUDC and NOAA GMD, 2) MOZAIC-IAGOS observations of upper tropospheric ozone from commercial aircraft, and 3) OMI satellite observations of mid-tropospheric ozone. We demonstrate that OMI spatial and seasonal patterns are consistent with ozonesonde data for the recent years (2012-2013), suggesting the OMI instrument is stable over more than 10 years of operation since 2004. Such consistency between OMI and ozonesonde data allows us to apply OMI data to test the tropospheric ozone simulation at global scale particularly in the tropics and the southern hemisphere where in-situ observations are limited and sparse. Compared to OMI 700-400 hPa ozone observations, the current standard GEOS-Chem simulation shows no global bias but distinct regional and seasonal patterns. The improved ability to model ozone compared to early model versions reflects the advancing scientific knowledge of atmospheric processes controlling global tropospheric ozone. We discuss its implications with a particular focus on recent model developments in meteorological input, lightning, isoprene chemistry, and tropospheric bromine chemistry.