Universal Mechanism for Quantitative Understanding of Global Ozone Depletion

Abstract: This paper formulates the cosmic-ray(CR)-driven electron-induced reaction (CRE) mechanism to provide a quantitative understanding of global ozone depletion. Based on a proposed electrostatic bonding mechanism for charged-induced adsorption of molecules on surfaces and on the measured dissociative electron transfer (DET) cross sections of ozone depletion substances (ODSs) adsorbed on ice, an analytical equation is derived to give atmospheric chlorine atom concentration: $$[Cl] = \sum_i k^i \theta_{ODS}^i \Phi_e^2,$$ where $\Phi_e$ is the CR-produced prehydrated electron ($e_{pre}^-$) flux on atmospheric particle surfaces, $\theta_{ODS}^i$ is the surface coverage of an ODS, and $k^i$ is the ODS's effective DET coefficient comprising the DET cross section, lifetimes of surface-trapped $e_{pre}^-$ and Cl$^-$, and particle surface area density. With concentrations of ODSs as the sole variable, our calculated results of time-series ozone depletion rates in global regions in the 1960s, 1980s and 2000s show generally good agreement with observations, particularly with ground-based ozonesonde data and satellite-measured data over Antarctica and with satellite data in the tropics in a narrow altitude band at 13-20 km. Good agreements with satellite data in the Arctic and midlatitudes are also found. A new insight into the denitrification effect on ozone loss is given quantitatively. But this equation overestimates tropospheric ozone loss at northern midlatitudes and the Arctic, likely due to increased ozone production by the halogen chemistry in polluted regions. Finally, ozone maps from ozonesonde data clearly reveal the scope of the tropical ozone hole. The results render confidence in applying the CRE equation to achieve a quantitative understanding of global ozone depletion.