finding obtained by Johnson et al. (2002). It follows from that some of the NECC streamlines in Nov. 2014 took clockwise rotations from the slow-down interval $140^{\circ}$W–$110^{\circ}$W and turned back coincidentally across the Niño-A region. In addition, the sensitivity of the Niño-B region is due to the existence of a high temperature sea-area off Central America. Any equatorward transport from this area may bring warm water to the equator.

It follows from that the inclined streamlines of the SSEC dominate most southeastern sea areas. In particular, some of them thrust at the central equatorial Pacific like swords, and they can transfer cold water into this area in a direct way. The variation of ${V}_2$ in verifies this. With this understanding, “Niña-A" region is delimited. In addition, notice that the Peru current along the coast of South America always supplies cold water to the NSEC and SSEC, its strength needs to be determined. Thus, Niña-B region is delimited. We note that the selection of these four sensitive regions had involved in many trials and the results shown in were under the best choice. For simplicity, we refer to the averaged equatorward velocities in Niño-A, Niño-B and Niña-B regions as the corresponding 