Heini Wernli

Research interests

My research started with extratropical cyclones, and I am still fascinated by them. They make our daily weather, they are so variable in terms of their evolution and impact, they are still associated with large forecast uncertainty, and they are key flow features in the climate system. A large part of the work of my research group has been focusing on understanding the processes involved in extratropical cyclones and on why, in some cases, they cause extreme weather. On this route, we’ve learned a lot about the importance of coherent airstreams in extratropical cyclones and about how the atmospheric water cycle, via phase changes and latent heating, affects the dynamics of cyclones and of the larger-scale embedding flow.

In INTEXseas, I would like to use this physical processes understanding of extratropical weather systems to a different set of questions. What determines whether a particular winter is unusually wet or dry? Why does the year-to-year variability of, e.g., winter temperature vary so strongly between different regions on the globe? And how will this variability, in particular the extremes, i.e., the wettest and driest season, change in the future climate? I expect that answering these questions will bring us, in many cases, back to cyclone dynamics: Why do several of them travel across the same region within a few weeks, leading to extended wet spells? Or why are they sometimes blocked from certain regions over weeks, leading to long-lasting dry periods? I am very grateful for the extremely generous support of this project from the EU, and to the excellent team of colleagues who like to investigate together many facets of extreme seasons. Seemingly simple questions. But most likely in the end complex and fascinating dynamics.