Sea Level Variations Due to Equatorial Rossby Waves Associated with El Nin˜o

Abstract

Abstract Interannual variations of sea level in the tropical Pacific are examined in relation to the El Nin˜o phenomenon. The amplitude of equatorial Rossby waves forced by wind and the sea level due to the waves are calculated from the analytical solutions in a two-layer reduced-gravity ocean model using filtered monthly wind data during the period 1961–87. Sea level variations with interannual periods at Truk, Ponape, and Majuro islands, located around 7°N, as well as at Rabaul, Honiara, and Funafuti in the South Pacific, are almost explained by Rossby waves remotely forced by winds. Reflected Rossby waves generated at the eastern coast of the Pacific may not significantly be effective. The interannual Rossby wave components of sea level are produced by odd meridional-mode waves excited from the equatorially symmetric component wind, which is composed of wind data in the same hemisphere as the studied sea level grid. Therefore, the Rossby components in the North Pacific are not affected by wind in the S...