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| Titel |
North Atlantic westerlies variability from ships' logbooks: 1685-2008 |
| VerfasserIn |
David Barriopedro, David Gallego, Ricardo García-Herrera |
| Konferenz |
EGU General Assembly 2014
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 16 (2014) |
| Datensatznummer |
250093725
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| Publikation (Nr.) |
 EGU/EGU2014-8724.pdf |
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| Zusammenfassung |
| A monthly index based on the persistence of the westerly wind over the English
Chanel is constructed for 1685-2008 using daily data from ships’ logbooks and
marine meteorological datasets. This Westerly Index (WI) provides the longest
instrumental record of atmospheric circulation currently available. Anomalous WI values
are associated with climatic signals in temperature and precipitation over large
areas of Europe, which are stronger for precipitation than for temperature and in
winter and summer than in transitional seasons. Overall, the WI series reveal that
the frequency of the westerlies in the eastern Atlantic during the 20th century or
the Late Maunder Minimum was not exceptional in the context of the last three
centuries.
The WI provides additional and complementary information to the North Atlantic
Oscillation (NAO) indices. Thus, there is a significant year-round signature on precipitation
and a seasonal-dependent temperature signal associated with the WI that is partially missed
by the NAO indices. Although the WI reveals an overall good temporal agreement with the
winter and high-summer NAO, there are several multidecadal periods of weakened
correlation during the industrial era. These decoupled periods are interpreted on the basis of
several sources of non-stationarity affecting the centres of the variability of the North Atlantic
and their teleconnections. Comparisons with long instrumental indices extending back to the
17th century suggest that similar situations have occurred in the past, which call for caution
when reconstructing the past atmospheric circulation from climatic proxies. In fact, there is a
generally poor correlation of the WI with purely proxy-generated indices of the NAO. |
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