PSCs and the Ozone Hole

The reaction between C10N02 and H20(s), which is very slow in the gas phase, also can occur  

The gaseous HOC1 rapidly photolyzes to yield a free chlorine atom. HOC1 itself can undergo a subsequent heterogeneous reaction (Abbatt and Molina 1992) 

FIGURE 5.19 Catalytic cycles in 03 depletion involving polar stratospheric clouds (PSCs). 

FIGURE 5.20 Schematic of photochemical and dynamical features of polar ozone depletion [WMO (1994), as adapted from Webster et al. (1993)]. Upper panel shows the conversion of chlorine from inactive reservoir forms, CIONO2 and HC1, to active forms, Cl and CIO, in the winter in the lower stratosphere, followed by reestablishment of the inactive forms in spring. Corresponding stages of the polar vortex are indicated in the lower panel, where the temperature scale represents changes in the minimum temperatures in the lower polar stratosphere. 

In the Antarctic winter vortex, vertical transport within the vortex as well as horizontal transport across the boundaries of the vortex is slower than the characteristic time for the ozone-depleting reactions. The local rate of loss of ozone can be approximated as that of the rate-determining step  

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