Effect of odd hydrogen on ozone depletion by chlorine reactions

The odd hydrogen species, especially OH and HO 2 are important in the chemistry of the natural stratosphere because of their direct reactions with O and O 3 and their role in nitrogen oxide (NO x ) cycles. When chlorine is added to the stratosphere the interaction of NO x , HO x and ClX species yields several potential feedback effects for O 3 perturbations, some stabilizing and some destabilizing. Here we focus on the effects of HO x on O 3 changes due to ClX injections. As ClX selectively attacks the ozone layer above 28 km the layer below tends to be thickened by the increased incidence of solarUV. If HO x densities are high they dampen this radiative feedback and prevent the healing at low altitudes. We demonstrate how the ozone‐layer shape changes under the influence of injected ClX for several choices of key HO x reaction rates. These same reaction rates exert partial control over the apportioning of Cl atoms among HCl, ClO and Cl, over the total amount of HO x , the ratios of OH to HO 2 and H 2 O 2 and the ratio of [NO + NO 2 ] to [HNO 3 ]. The uncertainty in these rates leads to at least a factor of three uncertainty in predicted ozone reductions due to ClX injections.