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| Titel |
On forecasting abnormal climatic events in the tropical Atlantic Ocean |
| VerfasserIn |
J. Servain, S. Arnault |
| 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 ; 13, no. 9 ; Nr. 13, no. 9, S.995-1008 |
| Datensatznummer |
250011986
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| Publikation (Nr.) |
 copernicus.org/angeo-13-995-1995.pdf |
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| Zusammenfassung |
| Modelling and observational evidence indicate
that interannual variabilities of dynamic height and sea surface temperature
(SST) in the eastern part of the tropical Atlantic Ocean (Gulf of Guinea) are
largely induced by preceding fluctuations in wind stress, mainly in the western
equatorial basin. A wind-driven linear ocean model is used here to test the
possibility of forecasting the abnormal dynamic heights. A control run of the
model, forced by 1964–1993 wind stress monthly means, is first conducted. Yearly
test runs (1964–1994) are subsequently performed from January to August by
forcing the model with observed winds from January to May, and then by forcing
with the May wind assumed to persist from June to August. During the last three
decades the largest deviations of dynamic height simulated by the control run in
the Gulf of Guinea in boreal summer would have been correctly forecast from wind
data related only to conditions in May of each year. However, for weak climatic
anomalies, the model may forecast overestimated values. For the most part (about
20 times during the last 30 years), the sign of the observed SST anomaly in the
centre of the Gulf of Guinea during the boreal summer is identical to the sign
of simulated anomalies of dynamic height deduced from both control and test
runs. Along the eastern equatorial waveguide, the sea level forecasting skill
slowly decreases from the first 2 weeks of June until the second 2 weeks of
August, but remains high on both sides of the equator throughout boreal summer,
as is expected from the adjustment in a linear ocean model. It is established
that throughout the year in the Gulf of Guinea the accuracy of the 1-month
forecast dynamic height anomaly provided by the simple linear method is greater
than that of the 1-month forecast assuming persistence. |
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