How Water Enters the Stratosphere

Earth9s stratosphere (from ~11 to ~50 km) contains much less water than would be expected based on the water vapor content at the boundary between the stratophere and the underlying troposphere. In her Perspective, Rosenlof discusses how this extreme aridity may arise. She highlights the report by Webster and Heymsfield, whose isotope data show that small-scale processes play an important role in the transport of water through the troposphere and into the stratosphere. These processes are not captured correctly by today9s models.