Connections between the stratosphere and synoptic variability

While US CLIVAR has traditionally focused on ocean-atmosphere coupling and its role on climate variability, in this edition of Variations we examine the coupling between the two lowest layers of the atmosphere, the troposphere and the stratosphere. The stratosphere, the region 10-50 km above the earth’s surface, exhibits variability driven by radiation, ozone chemistry, and momentum transport by a broad spectrum of waves propagating up from the troposphere. In the tropics, the stratospheric circulation is dominated by the verticallyoscillating pattern of downward propagating zonal winds known as the Quasi-Biennial Oscillation (QBO). In the extratropics of both hemispheres, the stratospheric polar vortex is a region of strong westerly circumpolar winds that persists through the fall and winter seasons. Increasingly, it has been recognized that variability in both the tropical and extratropical stratosphere can exert influence on surface climate.