Is there an equatorial Indian Ocean SST Dipole, Independent of the El NinoSouthern Oscillation?
Neville Nicholls, BMRC, Melbourne, Vic., Australia; and W. Drosdowsky A number of investigators have suggested the existence of a dipole in sea surface temperature (SST) between the east and west equatorial Indian Ocean, and proposed that the strength of this dipole may vary independently of the El Nio – Southern Oscillation. If such a dipole exists, in a statistical sense, then SST anomalies in the east and west equatorial Indian Ocean should be negatively correlated. In fact, except for the months of October and November, SST in the two regions are positively correlated (reaching a maximum of +0.68 in February). But any negative correlations between the two ends of the “dipole” are confounded by recent warming across most of the Indian Ocean, and by the relationship between Indian Ocean SST and the El Nio – Southern Oscillation. We have removed the effect of the warming trend and the El Nio – Southern Oscillation on both ends of the “dipole”, to examine whether a dipole does in fact
