Climatology of Vb cyclones, physical mechanisms and their impact on extreme precipitation over Central Europe

Messmer, M.; Gómez-Navarro, J. J.; Raible, C. C. (2015). Climatology of Vb cyclones, physical mechanisms and their impact on extreme precipitation over Central Europe. Earth system dynamics, 6(2), pp. 541-553. Copernicus Publications 10.5194/esd-6-541-2015

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Cyclones, which develop over the western Mediterranean and move northeastward are a major source of extreme weather and known to be responsible for heavy precipitation over the northern side of the Alpine range and Central Europe. As the relevant processes triggering these so-called Vb events and their impact on extreme precipitation are not yet fully understood, this study focuses on gaining insight into the dynamics of past events. For this, a cyclone detection and tracking tool is applied to the ERA-Interim reanalysis (1979–2013) to identify prominent Vb situations. Precipitation in the ERA-Interim and the E-OBS data sets is used to evaluate case-to-case precipitation amounts and to assess consistency between the two data sets. Both data sets exhibit high variability in precipitation amounts among different Vb events. While only 23 % of all Vb events are associated with extreme precipitation, around 15 % of all extreme precipitation days (99 percentile) over the northern Alpine region and Central Europe are induced by Vb events, although Vb cyclones are rare events (2.3 per year). To obtain a better understanding of the variability within Vb events, the analysis of the 10 heaviest and lowest precipitation Vb events reveals noticeable differences in the state of the atmosphere. These differences are most pronounced in the geopotential height and potential vorticity field, indicating a much stronger cyclone for heavy precipitation events. The related differences in wind direction are responsible for the moisture transport around the Alps and the orographical lifting along the northern slopes of the Alps. These effects are the main reasons for a disastrous outcome of Vb events, and consequently are absent in the Vb events associated with low precipitation. Hence, our results point out that heavy precipitation related to Vb events is mainly related to large-scale dynamics rather than to thermodynamic processes.

Item Type:

Journal Article (Original Article)

Division/Institute:

10 Strategic Research Centers > Oeschger Centre for Climate Change Research (OCCR)
08 Faculty of Science > Physics Institute > Climate and Environmental Physics

UniBE Contributor:

Messmer, Martina Barbara; Gomez, Juan Jose and Raible, Christoph

Subjects:

500 Science > 530 Physics
500 Science > 550 Earth sciences & geology

ISSN:

2190-4979

Publisher:

Copernicus Publications

Language:

English

Submitter:

Doris Rätz

Date Deposited:

04 Sep 2015 15:16

Last Modified:

04 Sep 2015 15:16

Publisher DOI:

10.5194/esd-6-541-2015

BORIS DOI:

10.7892/boris.71502

URI:

https://boris.unibe.ch/id/eprint/71502

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