Influence of subtropical dipole pattern in Southern Indian Ocean on ENSO event

Abstract

Subtropical Dipole Pattern (SDP) in southern Indian Ocean is another significant dipolelike sea surface temperature anomalies (SSTA) phenomena besides tropical Indian Ocean dipole (TIOD). It is very clear in interannual and interdecadal variations. But many recent studies have mainly aimed at the SST of equatorial Indian Ocean and less at southern Indian Ocean, especially less at the relationship between SSTA in southern Indian Ocean and El NinoSouthern Oscillation (ENSO). Present works investigated primarily the correlation between the SDP and ENSO. It is found that SDP event act as a crucial linkage between positive and negative ENSO phases. The SSTAs in equatorial eastern Pacific Ocean are completely reversed before and after SDP event. Further, we investigated the possible impact of SDP on ENSO event in interannual scale by researching the anomalous characteristics of sea temperature, wind, convergence and divergence, total cloud amount, radiation and so on. The results showed that the influence of SDP on ENSO involve not only the process of positive and negative air-sea feedback, but also the interaction between atmospheric circulation over tropical and subtropical, specially the eastward propagation of anomalous zonal wind from the equatorial Indian Ocean to the Pacific Ocean. Otherwise, it also relates, to some extent, to the transition of large-scale climatic mean flow over the Indian Ocean and Pacific Ocean.