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Surface area (cm2/cm3)

FIGURE 12.43 Model-predicted removal rates of odd oxygen as a function of particle surface area for 1990 levels of total chlorine and bromine at 20-km altitude and 43.5°N (adapted from Solomon et al., 1996).

Surface area (cm2/cm3)

FIGURE 12.43 Model-predicted removal rates of odd oxygen as a function of particle surface area for 1990 levels of total chlorine and bromine at 20-km altitude and 43.5°N (adapted from Solomon et al., 1996).

Antarctic ozone hole formation. Outflow to lower latitudes then provides a source of air that has been processed by the polar vortex and PSCs (e.g., see Prof-fitt et ai, 1990, 1993; Randel and Wu, 1995).

A second mechanism for the polar vortex to influence midlatitudes is during the breakup of the polar vortex in the spring when the vortex air becomes mixed with air at lower latitudes (e.g., see Manney et al., 1994a or 1994b). Similarly, Atkinson and Plumb (1997) suggest that on some occasions, ozone depletion observed at midlatitudes may be due to transport of ozone-depleted air from the Antarctic ozone hole. Finally, chemistry occurring on PSCs and aerosols in the region outside the edges of the vortex followed by transport to lower latitudes may influence midlatitude chemistry.

Evidence for each of these mechanisms of influence of the polar regions on midlatitudes is discussed in Chapter 4 of the WMO (1995, 1999) document.

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