Investigating changes in atmospheric circulations over Central Europe

Author: Pedro Herrera Lormendez

Organisation: Interdisciplinary Environmental Research Centre

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Abstract

As circulation patterns start responding dynamically to anthropogenic global warming, related changes may strengthen or reduce regional/local frequencies and intensities of extreme weather events. The use of an automated classification is used to derive daily circulation patterns and to evaluate past and future changes in their temporal frequencies over central Europe, focusing on Germany for the 1900–2100 period. Three reanalyses and eight global climate models from the coupled model intercomparison project, phase 6, were used, based on daily mean sea-level pressure data. Best agreement in deriving relative frequencies of the synoptic types was found between the reanalyses. Global models are generally able to capture the interannual variability of circulation patterns and their climatological state, especially for the less frequent synoptic types. Based on historical data and the shared socioeconomic pathway 5 scenario, the evaluated trends show more robust signals during April-September, given their lesser internal variability. Increasing frequencies were found for circulation types characterised by weak pressure gradients, mainly at the expense of decreasing frequencies of westerlies. Our findings indicate that, given a high-emission sce- nario, these signals likely emerge from past climate variability towards the mid 21st century for most altered circulation patterns.