Causes of interannual variability over the southern hemispheric tropospheric ozone maximum

摘要

We examine the relative contribution of processes controllingthe interannual variability (IAV) of tropospheric ozone over four sub-regionsof the southern hemispheric tropospheric ozone maximum (SHTOM) over a 20-yearperiod. Our study is based on hindcast simulations from the NationalAeronautics and Space Administration Global Modeling Initiative chemistrytransport model (NASA GMI-CTM) of tropospheric and stratospheric chemistry,driven by assimilated Modern Era Retrospective Analysis for Research andApplications (MERRA) meteorological fields. Our analysis shows that overSHTOM region, the IAV of the stratospheric contribution is the most importantfactor driving the IAV of upper tropospheric ozone (270 hPa), where ozonehas a strong radiative effect. Over the South Atlantic region, thecontribution from surface emissions to the IAV of ozone exceeds that fromstratospheric input at and below 430 hPa. Over the South Indian Ocean, theIAV of stratospheric ozone makes the largest contribution to the IAV of ozonewith little or no influence from surface emissions at 270 and 430 hPa inaustral winter. Over the tropical South Atlantic region, the contributionfrom IAV of stratospheric input dominates in austral winter at 270 hPa anddrops to less than half but is still significant at 430 hPa. Emissioncontributions are not significant at these two levels. The IAV of lightningover this region also contributes to the IAV of ozone in September andDecember. Over the tropical southeastern Pacific, the contribution of the IAVof stratospheric input is significant at 270 and 430 hPa in austral winter,and emissions have little influence.