The role of cyclones and potential vorticity cutoffs for the occurrence of unusually long wet spells in Europe ...

• Main Authors: Röthlisberger, Matthias, Scherrer, Barbara, De Vries, Andries-Jan, Portmann, Raphael
• Format: Article in Journal/Newspaper
• Language: English
• Published: ETH Zurich 2022
• Subjects: North Atlantic
• Online Access: https://dx.doi.org/10.3929/ethz-b-000559698; http://hdl.handle.net/20.500.11850/559698

The synoptic dynamics leading to the longest wet spells in Europe are so far poorly investigated despite these events' potentially large societal impacts. Here we examine the role of cyclones and potential vorticity (PV) cutoffs for unusually long wet spells in Europe, defined as the 20 longest uninterrupted periods with at least 5 mm daily accumulated precipitation at each ERA-Interim grid point in Europe (this set of spells is hereafter referred to as S20). The S20 occur predominantly in summer over the eastern continent, in winter over the North Atlantic, in winter or fall over the Atlantic coast, and in fall over the Mediterranean and European inland seas. Four case studies reveal distinct archetypal synoptic storylines for long wet spells: (a) a 7 d wet spell near Moscow, Russia, is associated with a single slow-moving cutoff-cyclone couple; (b) a 15 d wet spell in Norway features a total of nine rapidly passing extratropical cyclones and illustrates serial cyclone clustering as a second storyline; (c) ... : Weather and Climate Dynamics, 3 (3) ...