Ozone calculations with large nitrous oxide and chlorine changes

The purpose of this study is broadly to reinvestigate NO x ‐Cl x interactions relative to ozone control in the stratosphere, using the long‐established Lawrence Livermore National Laboratory one‐dimensional model. To obtain perspective on reasonably expected atmospheric perturbations, this study includes unrealistic conditions in the calculations, and several interesting or unexpected features are found. (1) By varying both NO x and Cl x over wide ranges, regions are found where ozone column reduction is linear and nonlinear in added chlorine or in added nitrogen oxides. (2) If the stratosphere had much less NO x than the natural amount, small chlorine increases would cause large reductions of ozone. (3) At high Cl x , a region of NO x ‐Cl x space is found where added NO x (at constant Cl x ) increases the ozone column, but no region was found where added chlorine (at constant nitrous oxide boundary condition) increases the ozone column. (4) The solar self‐healing effect in response to ozone reduction by increasing Cl x is much greater than that associated with ozone reduction by increasing nitrous oxide. (5) For any fixed amount of Cl x , the amount of chlorine nitrate in the stratosphere is decreased by added NO x , and an explanation for this effect is presented. (6) Any increase of stratospheric Cl x shrinks the rate profile of ozone destruction by NO x , and any increase of nitrous oxide shrinks the rate profile of ozone destruction by Cl x . (7) Total ozone changes linearly with Cl x until the rate of ClO + O exceeds that of NO 2 + O below about 30 km, and then it becomes nonlinear with downward curvature. (8) Removal of all Cl x and all HO x from the stratosphere has only a slight effect on the magnitude and shape of the altitude profile of the rate of ozone destruction by NO x . (9) The NO x and HO x families almost completely suppress the effect of 1 parts per billion by volume (ppbv) chlorine on ozone; but in the absence of NO x and HO x , even 1 ppbv chlorine is a powerful ozone‐destroying catalyst from the bottom to the top of the stratosphere. (10) In its altitude flexibility, Cl x destruction of ozone is qualitatively different from NO x and HO x destruction of ozone.