Systematic analysis of tropospheric NO₂ long-range transport events detected in GOME-2 satellite data

Abstract. Intercontinental long-range transport (LRT) events of NO₂ relocate the effects of air pollution from emission regions to remote, pristine regions. We detect transported plumes in tropospheric NO₂ columns measured by the GOME-2/MetOp-A instrument with a specialized algorithm and trace the plumes to their sources using the HYSPLIT Lagrangian transport model. With this algorithm we find 3808 LRT events over the ocean for the period 2007 to 2011. LRT events occur frequently in the mid-latitudes, emerging usually from coastal high-emission regions. In the free troposphere, plumes of NO₂ can travel for several days to the polar oceanic atmosphere or to other continents. They travel along characteristic routes and originate from both continuous anthropogenic emission and emission events such as bush fires. Most NO₂ LRT events occur during autumn and winter months, when meteorological conditions and emissions are most favorable. The evaluation of meteorological data shows that the observed NO₂ LRT is often linked to cyclones passing over an emission region.