Time-space Variability of Weekly to Monthly Period Equatorial Waves in the Pacific Ocean

Abstract:

Data from satellite altimetry are used to characterize wavelike variability in the tropical Pacific Ocean at periods of days to two months. This period band is of interest because the space-time scales of oceanic equatorial waves at these frequencies have historically made adequate observation of the variability difficult. These waves have zonal scales that are very large (exceeding 3000 km) and meridional scales that are relatively short (~100 km), making in situ measurements difficult, and the short temporal scales pose challenges for observation with satellite altimeters because the wave periods are short compared to orbit repeat periods. As a result, there has been relatively little progress since the early 1980s in characterizing and understanding these equatorial inertia-gravity and mixed Rossby-gravity waves. In this analysis, we seek to exploit the long zonal length scales of these high-frequency equatorial waves in an analysis of satellite scatterometer and altimeter data to shed new light on the properties and dynamics of these waves.

At periods of 2-14 days, there is clear evidence for the presence of several basin-scale equatorial wave modes, including mixed Rossby-gravity waves and inertia-gravity waves associated with baroclinic modes one and two. Here, we focus on equatorial Kelvin waves and mixed Rossby-gravity waves forced in the western Pacific, and examine their variability in time and space and their relation to wind.