Recent Changes in Storm Track over the Southeast Europe: A Mechanism for Changes in Extreme Cyclone Variability

Mihaela Caian,Oana Catrina,Florinela Georgescu,Mirela Pietrisi

doi:10.3390/atmos12101362

Mihaela Caian, Oana Catrina + Show 2 more

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https://doi.org/10.3390/atmos12101362

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Abstract

Recent changes in cyclone tracks crossing Southeast Europe are investigated for the last few decades (1980–1999 compared with 2000–2019) using a developed objective method. The response in number, severity, and persistence of the tracks are analyzed based on the source of origin (the Mediterranean Sea sub-domains) and the target area (Romania-centered domain). In winter, extreme cyclones became more frequent in the south and were also more persistent in the northeast of Romania. In summer, these became more intense and frequent, mainly over the south and southeast of Romania, where they also showed a significant increase in persistence. The regional extreme changes are related to polar jet displacements and further enhanced by the coupling of the sub-tropical jet in the Euro-Atlantic area, such as southwestwards shift in winter jets and a split-type configuration that shifts northeastwards and southeastwards in the summer. These provide a mechanism for regional variability of extreme cyclones through two paths, respectively, by shifting the origins of the tracks and by shifting the interaction between the anomaly jet streaks and the climatological storm tracks. Large-scale drivers of these changes are analyzed in relation to the main modes of atmospheric variability. The tracks number over the target domain is mainly driven during the cold season through a combined action of AO and Polar–European modes, and in summer by the AMO and East-Asian modes. These links and the circulation mode’s recent variability are consistent with changes found in the jet and storm tracks.

Highlights

The Mediterranean is a climate region of major interest in the context of climate change, recently referred to as a climate change and biodiversity hotspot, mainly due to its faster warming (0.3–0.4 ◦C per decade compared to about 0.2 ◦C in the global ocean) and to multiple hazards increasing its vulnerability [1,2]
We note that the annual mean increased over Western and Eastern Europe in the two most recent decades and there was a decrease over Central Europe and north of the Black Sea, which will be discussed later
In Southern and Southeastern Europe (Figure 12) the increased number of tracks were related to -East Atlantic-West Russian pattern (EAWR) (EAWR had a negative trend in P0 and P2, (Table S3)) and to +AMO’s northern teleconnection branch (AMO had a positive trend in P0 and P2, (Table S3))

Summary

Introduction

The Mediterranean is a climate region of major interest in the context of climate change, recently referred to as a climate change and biodiversity hotspot, mainly due to its faster warming (0.3–0.4 ◦C per decade compared to about 0.2 ◦C in the global ocean) and to multiple hazards increasing its vulnerability [1,2]. The impact on AMOC strength due to Mediterranean Sea changes in stratification, through increased precipitation and runoff discharges has been studied as a long-term mechanism of coupled variability [39]. Changes in these teleconnections due to external forcings under actual transient and future climate may have significant impacts at the regional scale [40,41,42]. We further propose and discuss a potential mechanism of the recent regional changes in extreme storm tracks in relation with changes in the atmospheric teleconnection modes of atmospheric circulation in Sections 3.3 and 3.4.

Data and Methods

Results

Recent Changes in Frequency

Conclusions