Increases in global tropospheric ozone following an El Nino event: examining stratospheric ozone variability as a potential driver

The stratosphere can strongly influence the interannual variability of tropospheric ozone. It has been discussed previously that tropospheric ozone can increase following an El Nino event, due to enhanced stratosphere/troposphere exchange (STE) of ozone. Here, we run a chemical-transport model for 5 years, covering a period including a strong El Nino event (1997-1998), and find that variability of ozone in the stratosphere is an almost negligible driver of modelled post-El Nino increases of ozone STE and tropospheric ozone abundances. Changes in the dynamics, affecting the cross-tropopause air-mass flux, may be far more important in driving these anomalies. Copyright. (C) 2011 Royal Meteorological Society