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| Titel |
Long-lived Rossby wave trains as precursors to strong surface cyclones over Central Europe |
| VerfasserIn |
V. Wirth, J. Eichhorn |
| Konferenz |
EGU General Assembly 2012
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 14 (2012) |
| Datensatznummer |
250061015
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| Zusammenfassung |
| It is well known that strong surface cyclones over Central Europe can, in specific
cases, be preceded by long-lived upper tropospheric Rossby wave trains. This study
investigates to what extent this is true in a climatological sense. The analysis is based
on 40 years of 12-hourly reanalysis (ERA-40) data. Composites are computed by
selecting the dates with the lowest 5% of surface pressure at a specific point in central
Europe.
The composite meridional wind at 300 hPa shows a pronounced wave train. It originates
over the Pacific ocean and travels eastward; after crossing Europe it splits following two
distinct tracks over the Asian continent. The wave train is statistically significant as early as
10 days prior to the strong surface cyclone, although it has a small amplitude at that time.
The composite wave train generally has a westward tilt with height. An index is
constructed that projects any given map of the 300 hPa meridional wind onto a target
pattern corresponding to the composite wave train. The index is used to quantify
the amount of variability which is hidden in the composite picture. A high index
value on a given day increases the likelihood of a strong surface cyclone a few days
later. |
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