The Interannual Cycle Features of the Tropical Pacific-Indian Ocean Associated Mode and Its Mechanisms

Based on the SODA ocean analysis data, the interannual cycle features of the tropical Pacific-Indian Ocean associated mode (PIOAM) are studied by means of wavelet analysis and synthetic analysis. It is pointed out that PIOAM has a quasi-biennial cycle and a 3-4-year cycle. Furthermore, the dynamic and thermal mechanisms of the PIOAM interannual cycle are analyzed. The results show that the anomaly of Walker circulation over the two oceans is the key factor which forms the PIOAM. The propagation and reflection of ocean waves and the horizontal and vertical heat transfer of ocean circulation also play an important role in the cycle of PIOAM.