Linking solar and atmospheric cycles
In 1987, Harry van Loon and Karin Labitzke (Free University of Berlin) embarked on more than a decade of collaboration, studying solar-atmosphere connections. They discovered a statistical link between the 11-year solar cycle and conditions in the Arctic stratosphere. This link appears when the quasi-biennial oscillation (QBO) of tropical stratospheric winds is in a particular mode. In the 1990s, van Loon and Labitzke extended the correlations to the Southern Hemisphere and (independently of the QBO) to parts of the summer tropopause.