AMS NYC/Long Island Chapter Seminar with Heini Wernli

American Meteorological Society's NYC/Long Island Chapter Seminars
at Columbia University, Sponsored by Columbia University's Fu Foundation
School of Engineering and Applied Science presents:

Heini Wernli
ETH Zurich, Switzerland

Thursday, November 13, 2014, 6:30 PM, Davis Auditorium, 412 Schapiro Center

"How well do we understand and can we predict extreme weather associated with extratropical cyclones?"

Abstract: In large parts of the extratropics, severe weather in the form of very intense rainfall, snowstorms and strong surface winds is associated with the passage of cyclones and their attendant fronts. These extratropical cyclones are everyday features on surface weather charts, but their detailed structure and evolution, and the involved physical processes all reveal a fascinating degree of case-to-case variability. As an effect, there is also a huge variability in the effects of cyclones with only a few of them causing extreme weather and high socioeconomic impact. In this seminar I will present first a selection of North American case studies to illustrate the linkage between cyclone lifecycles and extreme weather, and then discuss a selection of studies that tried to identify the physical ingredients that distinguish high impact cyclones from normal ones. The main conclusions will be that (i) variability is huge - there is not a single type of cyclone that can produce extreme weather, (ii) scale interactions are very important, in particular linkages between atmospheric water vapor transport, cloud formation, latent heating and atmospheric dynamics, and (iii) there are prediction issues on all scales, ranging from Rossby wave dynamics to cloud microphysics. In the outlook, I will emphasize the need for fundamental research to further improve the process understanding of atmospheric flow systems, and the key role in this undertaking of international field experiments and other forms of collaboration.

Hosts: Lorenzo Polvani and Jimmy Booth


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