Ozone destruction and production rates between spring and autumn in the Arctic stratosphere

In situ measurements of radical and long-lived species were made in the lower Arctic stratosphere (18 to 20 km) between spring and early autumn in 1997. The measurements include O_3, ClO, OH, HO_2, NO, NO_2, N_(2)O, CO, and overhead O_3. A photochemical box model constrained by these and other observations is used to compute the diurnally averaged destruction and production rates of O3 in this region. The rates show a strong dependence on solar exposure and ambient O_3. Total destruction rates, which reach 19%/month in summer, reveal the predominant role of NO_x and HO_x catalytic cycles throughout the period. Production of O_3 is significant only in midsummer air parcels. A comparison of observed O_3 changes with destruction rates and transport effects indicates the predominant role of destruction in spring and an increased role of transport by early autumn