Linking Synoptic Circulation Regimes to Atmospheric Blocking: A Weather Type-Based Approach

Atmospheric blocking is a prominent large-scale circulation feature characterized by quasi-stationary high-pressure systems that interrupt the typical zonal flow in the mid-latitudes, often leading to persistent and extreme weather phenomena. Despite its significance in shaping regional climate variability, the identification and characterization of blocking remain challenging due to its diverse spatial structures and temporal evolution. In this study, we investigate the potential of weather type (WT) circulation classification as a diagnostic metric for atmospheric blocking detection.

The study applies a weather type (WT) classification method specifically to days with atmospheric blocking events, aiming to determine if certain circulation patterns are consistently linked to blocking. Using a 500 mb pressure-based classification and a blocking index derived from geopotential height, the research investigates whether WT classification can effectively represent the flow patterns during these blocked states.

Our analysis demonstrates that clustering weather type (WT) indices around the onset of blocking events yields a small number of robust and physically meaningful circulation clusters. These WT clusters consistently capture distinct atmospheric configurations that commonly accompany the development of blocking, especially over the North Atlantic and Western Europe. Each cluster exhibits characteristic climatic signatures across multiple atmospheric pressure levels, including variations in geopotential height, temperature, and wind fields. The persistence and structure of these circulation patterns align closely with the dynamical features of blocking, indicating that WT-based classifications can effectively reflect the onset and potential evolution of blocked flow regimes.

By linking WT circulation regimes with blocking events, this study highlights the potential of synoptic classification methods as complementary diagnostics for blocking detection. This integrated approach supports improved understanding and representation of blocking in weather and climate models.

Acknowledgments
The work was supported by PREVENT project. This project has received funding from Horizon Europe programme under Grant Agreement No: 101081276.