The impact of extreme stratospheric eddy heat flux events on tropospheric weather and its representation in CMIP5 models

Planetary waves represent an important source of dynamical coupling between the stratosphere and troposphere. The coupling can be characterized by the eddy heat flux, which is proportional to the vertical group velocity according to linear theory. Extreme eddy heat flux events in the stratosphere are directly coupled to the troposphere via high-latitude stationary wave anomalies, which strongly impact tropospheric winds and temperatures in the Atlantic basin.

An analysis of models participating in the Coupled Model Intercomparison Project Phase 5 suggests that low-top models systematically underrepresent extreme eddy heat flux events in the stratosphere. In the case of extreme negative events this underrepresentation leads to biased high-latitude variability in the troposphere.