Reflection of intraseasonal equatorial Rossby waves at the western boundary of the Pacific Ocean

The present study focuses on the existence of equatorial Rossby waves at periods shorter than 180 days and on their potential reflection into equatorial Kelvin waves. Toward that objective, TOPEX/Poseidon sea level data are used from 1992 to 2002. No Rossby waves are evidenced at periods shorter than 100 days. At 120-day period, Rossby waves of first meridional mode dominate in the western part of the basin. Their reflection efficiency at the western boundary in energy is found to be around 40 - 45% of theoretical estimates for low-frequency waves reflecting at a perfect wall. It is suggested that the 120-day reflected Rossby waves contribute to a large extent to the generation of 120-day Kelvin waves and that they superimpose on the directly wind-forced Kelvin waves, hence reinforcing this signal.