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| Titel |
Investigation of weather anomalies in the low-latitude islands of the Indian Ocean in 1991 |
| VerfasserIn |
A. Réchou, S. Kirkwood  |
| 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 ; 33, no. 7 ; Nr. 33, no. 7 (2015-07-02), S.789-804 |
| Datensatznummer |
250121216
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| Publikation (Nr.) |
 copernicus.org/angeo-33-789-2015.pdf |
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| Zusammenfassung |
| Temperature, precipitation and sunshine duration measurements at
meteorological stations across the southern Indian Ocean have been analysed
to try to differentiate the possible influence of the Mount Pinatubo
volcanic eruption in the Philippines in June 1991 and the normal weather
forcings. During December 1991, precipitation on the tropical islands
Glorieuses (11.6° S) and Mayotte (12.8° S) was 4 and
3 times greater, respectively, than the climatological mean (precipitation is greater by more
than than twice the standard deviation (SD)). Mean sunshine duration
(expressed in sun hours per day) was only 6 h on Mayotte, although the
sunshine duration is usually more than 7.5 ± 0.75 h, and on the Glorieuses
it was only 5 h, although it is usually 8.5 ± 1 h. Mean and SD of sunshine duration are based on December (1964–2001 for Mayotte,
1966–1999 for the Glorieuses).
The Madden–Julian Oscillation (MJO) is shown to correlate best with
precipitation in this area. Variability controlling the warm zone on these
two islands can be increased by the Indian Ocean Dipole (IOD), El Niño,
the quasi-biennial oscillation (QBO) and/or solar activity (sunspot number, SSN). However,
temperature records of these two islands show weak dependence on such
forcings (temperatures are close to the climatological mean for December).
This suggests that such weather forcings have an indirect effect on the
precipitation.
December 1991 was associated with unusually low values of the MJO index,
which favours high rainfall, as well as with El Niño, eastern QBO and high SSN,
which favour high variability. It is therefore not clear whether the Mount Pinatubo volcanic eruption had an effect. Since the precipitation anomalies
at the Glorieuses and Mayotte are more or less local (Global Precipitation
Climatology Project (GPCP) data) and the effect of the Pinatubo volcanic
cloud should be more widespread, it seems unlikely that Pinatubo was the
cause.
Islands at higher southern latitudes (south of Tromelin at
15.5° S) were not affected by the Pinatubo eruption in terms of
sunshine duration, precipitation or temperature. |
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