Contribution to the ozone trend of heterogeneous reactions of ClONO2 on the sulfate aerosol layer

Abstract

A photochemical two‐dimensional model including a grid‐point temperature distribution calculated from long‐term circulation statistics has been used to assess the relative role of heterogeneous reactions of chlorine nitrate on background sulfate aerosols. The sulfuric acid weight percentage is calculated explicitly as a function of temperature and water vapor content. It is shown that the contribution of these reactions to the ozone trend in the 1980‧s accounts for about only 10% the ozone loss due to N2O5 + H2O during the Northern Hemisphere winter months at mid‐latitude and between 50–200 mb. The weight of these reactions, however, may substantially increase in the presence of larger aerosol loading. The reaction ClONO2 + HCl on sulfate aerosols is found to be of comparable importance with respect to ClONO2 + H2O, and it is found to represent a significant source of active chlorine in the Antarctic spring.