Scientists observed a connection between volcanic aerosols and ozone levels in the lower stratosphere during the EASOE campaign. They found that after volcanic eruptions, aerosols negatively impacted ozone concentrations. This study in Greenland during the winter of 1991-92 aimed to understand how aerosols and ozone interact in the stratosphere. The researchers used a lidar system to measure aerosol levels and launched ozonesondes to measure ozone. Despite not detecting PSC formation, the simultaneous measurements allowed them to study the interactions between aerosols and ozone in the stratosphere.