Rachel White, Climate Prediction Group, Barcelona, Spain


Heatwaves and Atmospheric Dynamics: A Role for Atmospheric Waveguides?


Recent heat extremes in the Northern hemisphere, including the 2003, 2018, and 2019 European heatwaves, were associated with planetary-scale atmospheric waves with near-zero phase speed; i.e., they remained in approximately in one place for days to weeks; these events are sometimes associated with multiple Rossby waves packets re-occurring in the same region with very similar phase, and have been named ‘Quasi-stationary waves’ (QSWs). What causes these waves to behave in this quasi-stationary way remains a topic of on-going research. In this talk I will review the role of atmospheric waves on European heat extremes, and present work showing the potential role of atmosphere waveguides on the occurrence of QSWs.
Previous work has shown links between waveguides in the zonal mean flow with extreme events and high amplitude Rossby waves. Here I present results studying atmospheric waveguides as a function of both time and longitude. I connect anomalously high amplitude QSWs in ERA-interim data to the presence of an upstream atmospheric waveguide in the preceding days. Upstream waveguides are up to twice as likely to be present when there is anomalously high QSW activity in Europe relative to times of anomalously low QSW activity.

I will show early results from analysis of a subset of CMIP6 model simulations, showing that historical simulations are capable of simulating observed waveguide statistics as a function of longitude. Under SSP585 there is some evidence that the frequency of waveguides may increase in the future, with potential implications for heatwave frequency.


Tuesday February 11, 11:15


Rossbysalen C609, Arrhenius laboratory, Svante Arrhenius väg 16C, 6th floor