In this collaborative project, the principal investigators will address some key questions relating to the dynamical interaction between the stratosphere and the troposphere on both, climate and weather forecasting timescales. In particular, the PIs will study how perturbations in the stratosphere may be able to exert an influence on the tropospheric circulation. In a three-pronged approach, reanalyses will be examined, simulations with idealized three-dimensional dynamical models, and simulations with a comprehensive troposphere-stratosphere model will be performed. Graduate students will participate in this research.