Annual period equatorial waves in the Pacific Ocean

This paper analyzes behavior of annual period equatorial waves and their role in oceanic variations, namely, the sea level displacement, zonal current, and sea surface temperature (SST) along the equator in the Pacific. Using a linear model forced by observed wind stress, the amplitudes and phases of the annual equatorial waves are calculated. The model equatorial waves are compared with the waves decomposed from Levitus' (1982) climatological density data. The modeled and decomposed first‐meridional‐mode Rossby waves of the two gravest vertical modes indicate common features that those waves are forced in the eastern Pacific and propagate to the central Pacific. These first‐meridional‐mode Rossby waves play a dominant role in the model sea level displacement and cause the westward propagating feature in the model surface zonal current in the central Pacific. The analysis suggests that the propagation of the surface zonal current is significantly responsible for the well‐known westward propagation of annual SST variation in this region. The modeled and decomposed Kelvin waves are significantly different, but the model suggests that the role of the annual Kelvin waves in the equatorial oceanic variations is smaller than that of the first‐meridional‐mode Rossby waves.