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Abstract

This chapter provides a comprehensive overview of stratosphere–troposphere interactions, with emphasis on the Southern Hemisphere. We introduce key concepts such as wave activity (Eliassen–Palm fluxes), the Charney–Drazin criterion for wave propagation, downward control, and radiative coupling. The chapter then explores the stratosphere’s influence on tropospheric timescales and the surface impacts of dynamical perturbations originating in the stratosphere. It delves into subseasonal to seasonal prediction, highlighting the enhanced forecasting skill derived from stratospheric dynamics. The discussion also addresses the impact of stationary waves and model biases on stratosphere–troposphere coupling. Furthermore, the chapter examines the stratosphere’s role in shaping tropospheric circulation over longer timescales, including the effects of climate change and the potential influence of the ozone hole. Finally, it investigates the interactions between the Quasi-Biennial Oscillation and the Madden–Julian Oscillation, providing a holistic view of the complex interplay between these atmospheric layers.