Semi-empirical models for chlorine activation and ozone depletion in the Antarctic stratosphere: proof of concept

Abstract. Two semi-empirical models were developed for the Antarctic stratosphere to relate the shift of species within total chlorine (Cl_y = HCl + ClONO₂ + HOCl + 2 × Cl₂ + 2×Cl₂O₂ + ClO + Cl) into the active forms (here: ClO_x = 2×Cl₂O₂ + ClO), and to relate the rate of ozone destruction to ClO_x. These two models provide a fast and computationally inexpensive way to describe the inter- and intra-annual evolution of ClO_x and ozone mass deficit (OMD) in the Antarctic spring. The models are based on the underlying physics/chemistry of the system and capture the key chemical and physical processes in the Antarctic stratosphere that determine the interaction between climate change and Antarctic ozone depletion. They were developed considering bulk effects of chemical mechanisms for the duration of the Antarctic vortex period and quantities averaged over the vortex area. The model equations were regressed against observations of daytime ClO and OMD providing a set of empirical fit coefficients. Both semi-empirical models are able to explain much of the intra- and inter-annual variability observed in daily ClO_x and OMD time series. This proof-of-concept paper outlines the semi-empirical approach to describing the evolution of Antarctic chlorine activation and ozone depletion.