Rossby Wave Breaking Archetypal Patterns, Processes and Projected Changes from the 20th (twentieth) to the 21st (twenty-first) Century

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The weather that typically occurs in the middle latitudes is driven in part by the jet stream - a corridor of strong winds found 8-13 km above ground - and atmospheric undulations associated with Rossby waves that propagate with it. These waves typically have a pattern that resembles a swell in the ocean, in that they are relatively broad and rolling. However, in certain circumstances, they can break, resembling closely the appearance of a wave breaking on a shoreline. When Rossby waves break in the atmosphere, they are frequently associated with high-impact weather phenomena like extended heat and cold waves, extreme precipitation, and atmospheric blocking that can significantly alter the path of the jet stream. These Rossby wave breaks can take on a variety of different shapes and sizes (i.e., flavors) which may determine where and how they modulate mid-latitude extreme weather. To date, a comprehensive analysis of the different wave breaking flavors has yet to be undertaken. The goal of this research is to understand the common flavors of Rossby wave breaking in the Northern Hemisphere in the present and future climate using machine learning. The investigators will assess the flavors of Rossby wave breaking in past observations and seek to identify how well climate models can represent such patterns and their associated impacts on the jet stream and weather. The proposed work will also explore how these Rossby wave break flavors, frequencies, and impacts may change over the 21st Century. Given the close linkage between Rossby wave breaking, the jet stream, and high-impact weather, a better understanding of these events in the present and future is societally important. The exploration of how Rossby wave break patterns change over the next century should shed light on a critical area of interest to both the science community and the broader public. As part of proposed activities, the investigators will mentor a graduate student as well as two undergraduate students. One undergraduate researcher will help to develop a real-time Rossby wave break tracking tool for operational forecasters, while the second will explore the impacts of changes in Rossby wave breaking over the climate-sensitive Mediterranean region. This research will thus serve to improve our fundamental understanding of these high impact events, train the next generation of scientists in the intersectional study of weather and climate, and provide information that is of interest to members of the research community, operational forecasters, and policy/adaptation decision makers.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.