Observational constraints on the kinetics of the ClO-BrO and ClO-ClO ozone loss cycles in the Arctic winter stratosphere

Abstract

Observations of the balloon-borne LPMA/DOAS remote sensing instruments performed in the Arctic stratosphere in February 1999 are used to constrain a photochemical model. Measurements of all relevant nitrogen, chlorine, and bromine species indicate that moderate heterogeneous chlorine activation occurred in a filament of the Arctic vortex. Model-measurement comparisons for OCIO serve as an indicator of how well various scenarios of the involved reaction kinetics, in particular of the CIO-BrO and the CIO-CIO cycles, reproduce the observations. Recent suggestions for the photolysis rate of the CIO dimer, the equilibrium constant between CIO dimer and monomer, the rate of the CIO-CIO association reaction, and the branching ratio of the CIO-BrO reaction are consistent with the observations. Formation of an unstable isomer of CIONO2 cannot be reconciled with the observations. Modeled odd oxygen loss rates can be larger by 10% to 20% for the updated reaction kinetics compared to standard recommendations. Copyright 2007 by the American Geophysical Union.