Four main scientific topics (ST) were identified. These are linked to dynamics (DYN) and chemistry (CHEM) of the Southern Hemisphere:
- ST-DYN1: Transport and mixing processes in the SH-UTLS
- ST-DYN2: Gravity waves in the SH-UTLS
- ST-CHEM1: Impact of the Antarctic vortex on the SH-UTLS
- ST-CHEM2: Influence of biomass burning and biogenic emissions on the SH-UTLS
At the time of writing of this proposal, the SouthTRAC campaign was just completed, so only some preliminary results can be shown here. One exceptionally clear result was that also at flight altitudes of the HALO aircraft significant ozone loss was observed. This ozone loss was also visible in aged air masses from the polar vortex, which had been transported to the mid-latitudes of the Southern Hemisphere. Figure 3.20 shows measurements of long lived gases and ozone in a filament of vortex air, which was peeled of the polar vortex. This filament was projected by the Lagrangian CLaMS model, but was not visible in ECMWF analysis data. The very sharp filament is observed in long-lived tracers (red and blue lines) but not in ozone (green line) indicating that ozone depleted air is transported to the mid-latitudes. The chemical depletion of ozone has also been observed in correlations between N2O as a long lived-tracer and ozone (Figure 3.21). The data in the upper right part of the diagram (red data points) show what is expected under unperturbed conditions (increasing ozone with decreasing N2O).