In a warming climate, the frequency and intensity of heat waves are generally expected to increase, but it is not clear yet to which extent these changes arise from thermodynamical or dynamical contributions. The main objective of this project is therefore to gain further insights into the possible role of atmospheric dynamics in modulating the statistical properties of future heat extremes.

For that purpose, the dynamical state of the atmosphere is characterized with mid-troposphere Euro-Atlantic weather regimes, which are long lasting and slowly evolving weather patterns (Hannachi et al., 2017; Grams et al., 2017). Furthermore, the dynamical systems theory is used to quantify the persistence, local dimension and co-recurrence of an atmospheric state (Faranda et al., 2017; Faranda et al., 2020). The local dimension and persistence provide information on the evolution of the atmospheric circulation, while the co-recurrence ratio is used to quantify the co-occurrence of dynamical configurations with temperature patterns related to heat waves. This approach is applied to characterize both heat waves and weather regimes.

These methodologies are used to quantify dynamic and thermodynamic contributions to heat waves and investigate the extent to which changes in heat extremes depend on weather regimes and thus on changes in the atmospheric circulation. In particular, possible changes in transition probabilities between different atmospheric states, their predictability and persistence, and their influence on heat waves are assessed. Finally, a qualitative approach is developed to select suitable CMIP6 members for robust projections of future heat waves, their predictability and associated uncertainties.

Institutions: Institute for Meteorology and Climate Research, Karlsruhe Institute of Technology (KIT)¹; Institute of Geosciences, University of Bonn²

Contact: Prof. Dr. Joaquim G. Pinto¹, Christian M. Grams¹, Ines Dillerup¹, Dr. Sebastian Buschow²