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Variations pluviométriques et connexions climatiques : l’exemple des aires de mousson indienne et ouest-africaine Volume 2, issue 4, Décembre 1991

Author
URA 909 du CNRS, Centre de Recherches de Climatologie Bâtiment Sciences Gabriel, BP 138 21004 Dijon cedex, France.
  • Page(s) : 259-64
  • Published in: 1991

The diagnostic study of the Indian and west African rainy monsoons cannot be reduced to a mere discussion of mean circulation in the lower layers of the atmosphere. It must also take into account the climate’s intrinsic variability (especially in terms of rainfall) as well as the relations between these fluctuations and the ocean/atmosphere system. Statistical analysis shows that despite their seasonal synchronism and shared sensitivity to certain aspects of tropical circulation (Hadley and Walker cell circulations, Tropical Easterly Jet), the moonsoon rains of India and west Africa are decorrelated when their interannual anomalies are taken into consideration. They also have different modes of variability: infraseasonal and quasi biennal rhythms associated with the influence of large-scale planetary-level oscillations (30-50 day oscillation, equatorial stratospheric wind oscillation and the southern oscillation) for India; and, for western Africa, the persistance over many years of anomalies and a greater influence of surface fields, atmospheric circulation of a regional scale (south-east flow, local convergences and African Easterly Jet, and Atlantic and world sea surface temperatures.