Westward Propagation of Annual Sea Level and Wind Signals in the Western Pacific Ocean

Abstract

Abstract The annual cycle of sea level variability is examined for the period 1976–1985 at seven stations that lie along the mere axis (near 7°N)) of the north equatorial countercurrent (NECC) sea level trough in the western Pacific. The technique of complex demodulation is used to describe the year to year modulation of the phase and amplitude of the annual cycle of sea level along this line. This technique reveals differences in the character of the annual cycle that are related to the occurrence of the El Niño/Southern Oscillation (ENSO) phenomenon. During non-ENSO time periods, the amplitude of the annual cycle averages 4–5 centimeters and increases towards the west at approximately 1 mm per degree of longitude. The annual cycle during thew periods also shows a phase propagation towards the west at about 50 cm/s, which is comparable to the Rossby wave phase speed at this latitude. During the ENSO events, the amplitude of the annual cycle averages 7–8 centimeters and increases towards the west at about...