Flores-Morales, A.L.; Parés-Sierra, A., and Gómez-Valdivia, F., 2012. Semiannual Kelvin Waves in the Northeastern Tropical Pacific.

Sixteen years of altimetry data has been used to analyze the seasonal sea surface height variability in the Northeastern Tropical Pacific (NeTP). Extended Empirical Orthogonal Functions revealed that a Semiannual Kelvin Wave (SKW), originated in the central equator (160° W), is responsible for most of the semiannual variability in the NeTP coast. The SKW propagated poleward, acting as a source of Rossby waves that contributed to the semiannual variability in the ocean interior. At ∼20° N the SKW vanished because of the abrupt change of the coastal tilt. Although the annual frequency dominates most of the variability in the NeTP, spectral analysis showed that in the eastern equator the semiannual frequency dominated, whereas along the coast, except for the Gulf of Tehuantepec, the amount of energy associated with the semiannual frequency was comparable to that associated with the annual one.