Large‐Scale Drivers of Persistent Extreme Weather During Early Summer 2021 in Europe. Issue 18 (27th September 2022)

• Record Type: Journal Article
• Authors: Tuel, A.; Steinfeld, D.; Ali, S. M.; Sprenger, M.; Martius, O.
• Is Part Of: Geophysical research letters. Volume 49:Issue 18(2022)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2022-09-27
• Subjects: Europe -- atmospheric dynamics -- weather extremes; Geophysics -- Periodicals; Planets -- Periodicals; Lunar geology -- Periodicals; 550
• DOI: 10.1029/2022GL099624
• Languages: English
• ISSNs: 0094-8276

Abstract

Abstract: The early summer of 2021 was a season of extremes across Europe. Heatwaves, droughts and wildfires hit Eastern Europe and the Baltic, while repeated extreme precipitation in Western Europe culminated in massive floods in mid‐July. The large‐scale circulation during this period was remarkably persistent, with an extremely meridionally amplified flow over Europe. Recurrent blocking over the Baltic and Rossby wave breaking in the North Atlantic led to frequent heavy precipitation in Western Europe and the Black Sea and to warm and dry conditions over Eastern Europe. These conditions persisted for a month as the blocks and wave breaking episodes strengthened one another, while three closely spaced extratropical transitions of tropical cyclones in the eastern North Atlantic led to recurrent amplification of the jet. Seasonal anomalies thus emerge from the complex interactions of individual weather events, offering an interesting storyline for climate impact assessment and a formidable challenge for (sub‐) seasonal prediction. Plain Language Summary: In the early summer of 2021, Europe experienced widespread weather extremes, including record‐breaking floods in Germany and prolonged heatwaves in the Baltic. These extremes resulted from a complex and particularly persistent atmospheric circulation over Europe and the North Atlantic. The interaction of three closely spaced tropical cyclones with the mid‐latitude circulation led to repeated amplification of the circulation, resulting in frequent wave breaking and blocking episodes that caused the weather extremes. Understanding what led to this unusual season has important implications for current and future climate risks, and is a first step toward improving sub‐seasonal forecast models to better capture such events. Key Points: Europe experienced unprecedented hot and wet extremes in the early summer of 2021 Extremes resulted from recurrent blocking and wave breaking caused by a persistent meridionally amplified flow over the Atlantic Three extratropical transitions of hurricanes in close succession were critical in repeatedly amplifying the flow