The signature of the main modes of climatic variability as revealed by the Jenkinson-Collison classification over Europe

Abstract

The Jenkinson-Collison Weather Typing (JC-WT) method uses sea-level pressure gradients to create 27 types based on the geostrophic flow and vorticity around any extratropical target location. Typically, JC-WTs are applied over specific locations or limited domains, thus hampering the understanding of the impact of large-scale mechanisms on regional climate. This study explores the links between regional climate variability, as represented by the JC-WTs, and large-scale phenomena, to describe the synoptic-scale variability in the North Atlantic-European region and evaluate the JC-WT methodology. Large-scale circulation is here characterized by major atmospheric low-frequency modes, namely the North Atlantic Oscillation, the East Atlantic and the Scandinavian teleconnection indices, and by atmospheric blockings. Results show that JC-WTs coherently capture the spatial and temporal variability of the large-scale modes and yields a characteristic response to blocking events. Overall, our results underpin the exploratory potential of this method for the analysis of the near-surface circulation. These findings endorse the use of JC-WTs and support the reliability and utility of the JC-WT classification for process-based model assessments and model selection, a crucial task for climate impact studies.