The study looked at how changes in the stratosphere's temperature and ozone levels can affect weather patterns in the troposphere. They found that when the stratosphere gets very cold above a warm air mass in the troposphere, ozone levels can drop significantly. This happens when the tropopause (boundary between troposphere and stratosphere) is high and the middle stratosphere is cold. The researchers also discovered that extreme ozone depletion occurs when vertical air movements in both layers are in the same direction. This correlation was observed during specific weather events in Europe over several years. Overall, the study shows how interactions between different layers of the atmosphere can impact ozone levels and weather systems.