Exploring the driving forces of long-term total ozone change: based on data from a ground based station at the northern mid-latitude over 1958–2018.

The driving forces controlling the long-term total ozone change are investigated using the total ozone data from Edmonton (53.55°N, 114.0°W), Canada, over 1958–2018. By using the slow feature analysis method, the driving force signal for monthly mean total ozone time series is extracted. It is found that the driving force has fluctuated at higher values since the mid-1980s, and the corresponding total ozone has varied at lower values. These variation patterns indicate that the ozone loss since the mid-1980s is correlated with the higher values of the driving force. It is also found that the driving force exhibits sharp values following some explosive volcanic events, indicating that explosive volcanic eruptions act as a driving factor for ozone depletion. In order to analyze the scale structure of the driving force, the wavelet analysis method is applied. The results show that the spectral scales of the driving force peak at 2.4, 7.0, 21.4, 28.5, and 42.8 years. Among them, the 21.4 year periodicity, which corresponds to the 22-year solar magnetic cycle, is the basic one, and it modulates other mode of oscillations. More importantly, the 21.4 year cycle is modulated in amplitude by a signal with a much longer time scale. This long-scale modulating signal represents the impacts of the ozone depleting substances (ODSs) in the stratosphere, and it controls the long-term evolution of total ozone. Since the turn of the century, as the ODSs decline, a slow recovery of total ozone is expected. [ABSTRACT FROM AUTHOR]