The influence of the Indian Ocean dipole mode on precipitation over the Seychelles

Correlation and composite analysis are applied to study the atmospheric-oceanic mechanisms related to precipitation on the largest island of the Seychelles archipelago, Mahé, in the equatorial western Indian Ocean (EWIO). Significant relationships are found to exist between precipitation and a reversal in zonal wind in the equatorial Indian Ocean (IO), cooler sea surface temperatures (SSTs) in the eastern and southern IO and convergence over Eastern Africa. The observed SST and zonal wind anomalies affecting rainfall in the EWIO are also characteristics of the dipole mode, an Indian Ocean event of internal variability measured by the dipole mode index (DMI). The September-October-November DMI is significantly correlated to December-January-February precipitation in the EWIO, explaining up to 20% of the variance. The analysis suggests an additional influence on variability of rainfall over the EWIO by the sea surface temperatures of the southwest Indian Ocean. Copyright © 2006 Royal Meteorological Society.