the scenarios in 2009/10 and 2015/16. In addition, the two Niña indices had also taken part in all these processes, and the intensity of its weakening affected that of El Niño.

In addition to clarifying the relationship between the current indices and the SST anomalies, there is a need to compare the evolutions of the zonal currents and the corresponding SSTs. The comparison between and indicates that, before the occurrences of El Niño events, the NECC had already strengthened (the leading times varied from several months to 2 years), and the rapid gathering of heat led to a drastic temperature increase in the sea area off Central America. This finding accords with the result given by Wyrtki (1973). Moreover, shows that the SSEC had weakened accordingly with almost the same leading time. Hence, prior to the occurrence of El Niño, the NECC and the SSEC (together with the NSEC) had finished adjusting in a harmonious manner, which was possibly caused by a unitary change in the wind field.

It follows from and that, in the EP, the temperature on the equator is always lower than that of the northern region that the NECC passes through, and higher than that of 