Factors controlling global tropospheric ozone: roles of isoprene chemistry, tropospheric halogen chemistry, convection, and lightning NOx sources

Abstract:

Ozone is central to our understanding of tropospheric oxidant chemistry through its driving of radical cycles. Yet our understanding of factors determining its spatial distribution and long-term trend is still poor. In this work, we use the GEOS-Chem chemical transport model as a platform to test our current knowledge of key factors controlling tropospheric ozone. We evaluate the most recent GEOS-Chem simulation against in-situ data using ozonesonde networks from WOUDC and NOAA-GMD and using aircraft observations from MOZAIC/IAGOS, to examine the vertical distribution of modeled tropospheric ozone. Satellite observed ozone data from OMI (Ozone Monitoring Instrument) are used to assess the spatial distribution of the predicted ozone concentrations. We also examine different versions of GEOS-Chem outputs from historical benchmarks and from sensitivity runs (such as changing in chemistry and meteorological fields) for their capabilities to reproduce observed tropospheric ozone patterns. In this presentation, we interpret these analyses in terms of present understanding in isoprene chemistry, tropospheric bromine chemistry, lightning NO_x sources and deep convection, and examine their implications for key model processes controlling the abundance and variability of global tropospheric ozone.