Contrasting SST anomalies over the Indian Ocean between the two types of El Ni~no events during boreal autumn
The present work investigates the different impacts of sea surface temperature (SST)anomalies over the tropical In-dian Ocean as associated with two types of El Ni~no events during boreal autumn,based on the observed data sets from 1951 to 2010.Here,we focus on the relationship between the Indian Ocean Dipole (IOD)and these two types of El Ni~no.It is shown that the positive IOD-like SST anomaly occurs for both EP and CP El Ni~no autumns,but with a different probability.Most of EP El Ni~no events are accompanied by a strong positive IOD-like SST anomaly.However,a weak positive IOD-like SST anom-aly appears for only half of the CP El Ni~no events.It seems that there is a strong relationship between the intensity of IOD and that of EP El Ni~no.That is,IOD tends to occur during the strong EP El Ni~no autumns,with a strong sinking current and neg-ative rainfall anomaly over the maritime continent.During the CP El Ni~no,however,the occurrence of IOD seems to be unre-lated with the strength of CP El Ni~no.The location of the CP El Ni~no is a possible key effect on the intensity of IOD in au-tumn.For the CP El Ni~no autumns when an obvious IOD appears,the warming SST anomaly is located slightly eastward over the central Pacific with a strong sinking current and severe drought over the maritime continent,as well as a significant easterly anomaly over the tropical Indian Ocean.While in the CP El Ni~no autumns during which no positive IOD-like SST anomaly oc-curs,the Pacific warming SST anomaly is located relatively further west.The very weak anomalous sinking motion seems lim-ited help to sustain the SST anomaly over the Indian Ocean.
Two types of El Ni~no eventsIndian Ocean Dipole (IOD)Atmospheric response