Wintertime Polar Ozone Evolution during Stratospheric Vortex Break-Down

Abstract

This winter, a record ozone loss was observed over the Arctic resulting in an unprecedented ozone hole that earned a large social attention. As chlorofluorocarbons continue to decline due to the Montreal protocol, random ozone destructions still occur in the polar region when the circumpolar flow above 20 km (“stratospheric polar vortex”) suddenly warms up and weakens. This unusual vortex event enhances downward intrusion of ozone-destroying chemical species from the upper atmosphere to the stratosphere. In this study, the behavior of polar ozone related to major sudden stratospheric warming events (SSW) was investigated. Specifically, air circulation and chemistry of ozone destroying species (NOx and CO) are examined during three realistic major SSWs and compared with a non- SSW winter. The simulated ozone during SSW showed anomalies in several regions. A “primary” ozone layer (near 40 km) experiences strong perturbation due to horizontal mixing. The “tertiary” maximum at 72 km displaces 5 km upward by intensified air movement above weakened vortex. The concentration of the “secondary” maximum (90- 110 km) increases by ~34% that appears to be related to the enhanced descent of nitrogen oxides and carbon monoxide. Unusual downwelling of ozone destroying species extends to the “primary” maximum and potentially can greatly contribute to the spring time ozone destruction. The observed anomalies demonstrate significant natural impact on ozone chemistry and dynamics that occur in conjunction with anthropogenic influence. This information can be used to predict the occurrence of ozone loss in the future and to validate NCAR (National Center for Atmospheric Research) model, widely used for atmospheric studies.