Rossby Wave Packets in a Changing Climate and Implications for Weather Extremes in Europe

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As the concentration of greenhouse gases in the atmosphere increases, climate model projections agree on global thermodynamic responses such as the rise of the mean surface temperature or the increase in water vapor. However, the warming is not distributed uniformly, which induces large uncertainties in the response of the atmospheric circulation at both the global and the regional scale. These uncertainties prevent one from making robust statements about the future characteristics of weather extremes in specific regions. The proposed work will apply recently developed diagnostics for Rossby wave packets to a multi-member climate model ensemble in order to investigate changes in their characteristic properties and distinguish these changes from internal climate variability. The key novelty of these diagnostics is that they are local in space and time and, therefore, well suited to explore the interplay between Rossby wave packets and smaller-scale flow features like cyclones and blocks. In addition, the project will define and investigate an eddy-free background state that is truly independent of the waves, helping to disentangle trends in wave properties from trends in the zonal mean flow. Finally, these analyses will be used in order to investigate how changes in atmospheric circulation affect temperature and precipitation extremes in specific regions and, especially, in Europe.