Dynamic drivers of an extreme heatwave over the UK in July 2022

Abstract

Abstract Slow‑moving synoptic structures have been hypothesized to be a part of severe heatwave events over extended continental regions in summer, highlighting the potential impacts of the growing climate emergency associated with rising background temperatures. In this context, a slow‑moving synoptic structure from 16 to 19 July 2022 is investigated using a potential vorticity (PV) framework and Q‑vector analysis. The analyses reveal the development and maintenance of a temporally evolving three‑dimensional, self‑sustained structure associated with the extreme heatwave that affected Western and Northern Europe, centred over the United Kingdom (UK). PV anomalies at upper levels and the surface were semi-stationary and in lock-phase during this heatwave period, due to an environment in which a local circulation cell develops related to the sea surface temperature (SST) anomalies and the exit of the upper-level jet stream. Q-vector analysis emphasises that the location of the exit is also responsible for the evolution and movement of the heatwave over the UK. Both Q-vector and PV theories provide theoretical explanations for the mechanisms and characteristics of the dynamic heatwave drivers.