The Southern Oscillation / Northern Oscillation Cycle Associated with Sea Surface Temperature in the Equatorial Pacific

Abstract: This paper analyzed the time evolution of the global 1000 hPa height anomalies related to the sea surface tem-perature (SST) in the eastern equatorial Pacific by using ECMWF data in the period 1979-1988, in which two Pacific warm events, 1982/83 and 1986/87, are included. It is found that there are distinct evidences of eastward propaga-tion of alternate positive / negative height anomalies not only in the tropical South Pacific but also in the tropical North Pacific. The former is associated with the Southern Oscillation (SO) and the latter is associated with the so-called Northern Oscillation (NO).It is noteworthy that the alternate positive / negative anomaly centers associated with SO and NO can be traced back to the middle and higher latitudes of the South Indian Ocean and the East Asian continent respectively, which may be significant for the understanding of the causes and mechanism of SO and NO and for the monitoring of ENSO.Furthermore, these evolution processes have a strong symmetry about the Northern and the Southern Hemi-sphere. The whole SO / NO cycle takes about 3.5 years from extreme positive to negative index pattern and again from extreme negative to positive index pattern, It is suggested that the anomalous cold air activities over East Asia and Australia and the polar vortex activities over the northern and the southern Pacific seem to have dominant role on the SO / NO cycle.

Keywords:
• El Nino,
• Southern Oscillation,
• Northern Oscillation