Large-scale drivers of extratropical storm track biases in CMIP6 historical simulations

Abstract:

Extratropical cyclones are the leading driver of the day-to-day weather variability and wintertime losses for Europe. In the latest generation of coupled climate models, CMIP6, it is hoped that with improved modelling capabilities come improvements in the structure of the storm track and the associated cyclones. Using an objective cyclone identification and tracking algorithm the mean state of the storm tracks in the CMIP6 models is evaluated. Focus will be on both the Northern and Southern Hemispheres for both winter and summer seasons. Any developments and improvements since the previous generation of models in CMIP5 are discussed, with focus on the impact of model resolution on storm track representation. Furthermore, large-scale drivers of any biases are investigated, with particular focus on the role of atmosphere-ocean coupling via associated AMIP simulations, and also the influence of large-scale dynamical and thermodynamical features. Several of the persistent and robust biases evident in CMIP5 are improved in CMIP6, with further improvements in AMIP models.