Atlantic SST gradient and the influence of ENSO

The relationship between the boreal winter El Nino SST anomaly and boreal spring tropical Atlantic SST gradient (North Atlantic minus South Atlantic) is investigated using a long, detrended SST record. For both El Nino and La Nina, concordant cases (same sign for NINO3 index and Atlantic SST gradient) slightly dominate over discordant ones, reflecting the fact that the NINO3 index correlates more strongly with the North Atlantic than the South Atlantic SST anomaly. The ratio of the numbers of concordant and discordant cases is 4:3 overall, indicating strong non-ENSO influences on the Atlantic SST gradient. The composite of the concordant cases shows an SST anomaly in the North Atlantic with the same sign as NINO3 and an opposite-signed anomaly off the southwest coast of Africa resembling "Benguela Nino''. That of the discordant cases is dominated by a pre-existing SST anomaly with the same sign as NINO3 in the south-central South Atlantic.