Extreme low ozone episodes called ozone mini-holes are characterized by a quick and small-scale decrease in total ozone amount followed by an equally rapid recovery after a few days. These anomalous events have been observed in both hemispheres in winter or early spring. In mid-latitudes, these episodes can be explained by different dynamic processes such as the displacement of the polar vortex, the influence of planetary waves, the advection from the tropics of air patches with low total ozone content and vertical uplift of isentropic air-mass in the lower and middle stratosphere.
The following article analyses the main characteristic of these anomalous events: