title: Record Balkan floods of 2014 linked to planetary wave resonance.
abstract: In May 2014, the Balkans were hit by a Vb-type cyclone that brought disastrous flooding and severe damage to Bosnia and Herzegovina, Serbia, and Croatia. Vb cyclones migrate from the Mediterranean, where they absorb warm and moist air, to the north, often causing flooding in central/eastern Europe. Extreme rainfall events are increasing on a global scale, and both thermodynamic and dynamical mechanisms play a role. Where thermodynamic aspects are generally well understood, there is large uncertainty associated with current and future changes in dynamics. We study the climatic and meteorological factors that influenced the catastrophic flooding in the Balkans, where we focus on large-scale circulation. We show that the Vb cyclone was unusually stationary, bringing extreme rainfall for several consecutive days, and that this situation was likely linked to a quasi-stationary circumglobal Rossby wave train. We provide evidence that this quasi-stationary wave was amplified by wave resonance. Statistical analysis of daily spring rainfall over the Balkan region reveals significant upward trends over 1950-2014, especially in the high quantiles relevant for flooding events. These changes cannot be explained by simple thermodynamic arguments, and we thus argue that dynamical processes likely played a role in increasing flood risks over the Balkans.
authors.affiliation: Potsdam Institute for Climate Impact Research, Earth System Analysis, 14473 Potsdam, Germany.; Christian-Albrechts-Universität zu Kiel, 24118 Kiel, Germany.
authors.forename: Lisa
authors.initials: L
authors.lastname: Stadtherr
authors.affiliation: Potsdam Institute for Climate Impact Research, Earth System Analysis, 14473 Potsdam, Germany.
authors.forename: Dim
authors.initials: D
authors.lastname: Coumou
authors.affiliation: Potsdam Institute for Climate Impact Research, Earth System Analysis, 14473 Potsdam, Germany.
authors.forename: Vladimir
authors.initials: V
authors.lastname: Petoukhov
authors.affiliation: Potsdam Institute for Climate Impact Research, Earth System Analysis, 14473 Potsdam, Germany.
authors.forename: Stefan
authors.initials: S
authors.lastname: Petri
authors.affiliation: Potsdam Institute for Climate Impact Research, Earth System Analysis, 14473 Potsdam, Germany.; University of Potsdam, 14469 Potsdam, Germany.
authors.forename: Stefan
authors.initials: S
authors.lastname: Rahmstorf
mesh_terms: D063368:Balkan Peninsula; D057231:Climate Change; D055867:Cyclonic Storms; D004190:Disasters; D055868:Floods; D006801:Humans; D008522:Mediterranean Sea; D013816:Thermodynamics
keywords: Flooding; Rossby Waves; Vb-cyclone; Wave-resonance; climate change; extreme weather