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| Titel |
Recent changes in measured wind in the NE Atlantic and variability of correlation with NAO |
| VerfasserIn |
P. A. Pirazzoli, A. Tomasin, A. Ullmann |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
0992-7689
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| Digitales Dokument |
URL |
| Erschienen |
In: Annales Geophysicae ; 28, no. 10 ; Nr. 28, no. 10 (2010-10-25), S.1923-1934 |
| Datensatznummer |
250016900
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| Publikation (Nr.) |
 copernicus.org/angeo-28-1923-2010.pdf |
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| Zusammenfassung |
The paper deals with wind measurements, recorded since the 1950s, at twelve
meteorological stations along a transect near the westernmost European
border, between 64° and 44° N. Extreme wind speed tends to decrease
sharply near the northern boundary (at Reykjavick), near the middle of the
study area (at Shannon and Valentia) and near the southern boundary (at
Brest and Cap Ferret), to increase at Thorshavn, with less significant
trends at the other stations. Average wind speeds confirm the above
tendencies, with an additional increasing speed at Lerwick, Kirkwall,
Malin Head, Belle-Ile and Cap Ferret.
To compare changes in wind activity, the data have been subdivided into
three periods: until 1975, 1976–1992 and 1993–2008. Frequencies have been
computed also for the "winter" (October to March) period, per quadrants,
and for occurrences exceeding the speed of 15 m s−1.
At Reykjavick a recent increase in the frequency of strong winds has
occurred from various directions. Between 62° N (Thorshavn) and 59° N
(Kirkwall) strong wind has been increasing since 1975. Minor changes can be
observed at Stornoway, whereas at Malin Head the greatest increase for
southerlies and westerlies is observed during the 1976–1992 period. At
Belmullet, the frequency of strong southerlies has almost doubled since
1992, while at Shannon and Valentia it remains quite low. Finally at Brest
and Belle-Ile, westerlies are predominant among winds >15 m s−1.
Important changes in time and latitude appear in the correlation with the
NAO (North Atlantic Oscillation) index. The highest correlation
coefficients, calculated with monthly or seasonal means between the early
1950s and 1975, are observed from between 58° N (Stornoway) and
Iceland, whereas low positive coefficients are reported more south. During
the period 1976–1992, when increasing NAO index is predominant, positive
correlation improves southwards as far as 54° (Belmullet) with some
improvement also at Shannon and Valentia, while it remains low or even
negative near the French Atlantic coast. Finally in the 1993–2008 period,
correlation improves for all the stations south of 54° N (Belmullet), while
it weakens more north. |
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