Stratosphere-Troposphere Coupling Studies

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Over the past several decades, the composition and circulation of the stratosphere have changed, as the ozone layer has thinned and concentrations of greenhouse gases have increased. In the coming decades, the ozone layer is expected to recover against a background of continued increases in greenhouse gas concentrations. These stratospheric changes are important, because they can affect tropospheric weather and climate, especially at high latitudes. Our poor understanding, however, of the role of the stratosphere introduces uncertainty in climate projections, especially because we do not understand what is required of climate models to simulate realistic effects of stratospheric changes on surface climate.A wide variety of model results, together with observations, will be used to improve understanding of stratosphere-troposphere coupling and of how weather and climate are affected by stratospheric variability. A specific goal of this project is to gain an understanding of what is required in climate models to obtain realistic simulations of the effects of stratospheric changes, as well as effects of the quasi-biennial oscillation (QBO), on surface climate and weather. The QBO is fairly regular, and is generally predictable many months in advance, so relationships with the troposphere have the potential to improve long-range weather and climate forecasts. This work will contribute to our understanding of how stratospheric change will affect tropospheric climate, and through involvement in international efforts, contribute to scientific assessments of climate change and changes in atmospheric composition.Activities with broader impacts include: teaching middle school classes on climate change; supporting and training a postdoc; making data publicly available for download (e.g., annular mode indices); involving undergraduate students in the research project; organizing international conferences; and preparing a review of stratosphere-troposphere coupling, to be published in Reviews of Geophysics. This project will contribute to the World Climate Research Programme's Stratospheric Processes and their Role in Climate (SPARC) project.