Downward Influence from the Stratosphere in the Extratropics
Evidence from models and observations that the stratosphere imparts a significant downward influence on near-surface weather and climate has grown steadily since landmark papers in the early 2000s. It is now clear that the large-scale circulation in the stratosphere can be usefully exploited by seasonal forecasts, and that changes in this circulation are highly relevant both for understanding regional climate change in the past and projecting such changes into the coming century. Understanding the mechanisms behind this influence has proven to be quite challenging, but a number of recent studies have made significant progress in clarifying the relevant processes. This talk will summarize some of the established results in this area, argue for some points where real progress has recently been achieved, and speculate on some ongoing challenges and open questions.