Global Transport of Ozone

The three principal ~chanisD8 for large scale atmospheric transport of tropospheric ozone [injection from the stratosphere, transport from regions of net production in the boundary layer and distribution of °3 precursors resulting from either stratospheric injection or surface emissions] are examined in the light of current observations. While the actual °3 climatology may be much more complex than it currently appears, the limited data suggests that ozone in the Southern Hemisphere and the northern tropics and subtropics is strongly influenced by transport from the stratosphere. At this time, the major questions are in the southern tropics and the northern mid-latitudes. The high levels of ozone observed over South America appear to be either the result of local chemical production or transport from higher latitudes. Both the latitude gradient and the seasonal cycle in the northern mid-latitudes suggest a significant, if not dominant, role for the transport of both °3 and its precursors from source regions in the boundary layer, though transport from the upper troposphere also pays a role.