Abstract On the basis of the altimeter data between October 1992 and May 2007, the interannual variations of sea level anomalies (SLA) of the tropical Pacific Ocean are investigated. It is found that:1) Sea level anomalies during the period of 24-42 months (SLA_2442) are associated with the interannual variations of ENSO; 2) SLA_2442 circuit exists not only during strong ENSO terms like the El Nio of 1997/1998, but also with weak El Nio events, such as the El Nio of 1994/1995, and even in normal years; 3) Each circuit of SLA_2442 signals is cyclonic in both of the north and south hemispheres, whose pattern looks like an “O”, but not symmetrical. In addition, the circuit pathways are near 0°, 9.86°N and 8°S,respectively.
