How Mesoscale Eddies Masquerade as Rossby Waves in Newly Merged
Altimetric Products?
Abstract
Limited by under-sampling spatiotemporal resolution of satellite
altimeters, isolated and oval closed eddies can appear as wave-like
patterns. This problem hindered the definitely extraction of oceanic
Rossby waves in former researches. The unprecedented sampling capability
of the simultaneously operating six altimeters during 2016
~ 2019 opens an opportunity to separate Rossby waves
from Mesoscale-eddies. In this paper, the sampling density of newly
altimetric products is analyzed and a series of 2-dimensional finite
impulse response band-pass filter is used to decompose the propagating
signals. The results demonstrate that filtered wave-like patterns are
mainly attribute to mesoscale-eddies and the specialized filter fail to
distinguish them directly. More importantly, the spurious wave-like and
real Rossby wave signals can be quantified by re-filtering the
preliminary eddies field. The dominant wave signals are generally
observed for biannual and annual Rossby waves in three major basins and
the maximum more than 25% of observed signals in mid-latitude Pacific.
The Southern Indian Ocean has the most significant annual periods
signals which may implicate the role ofEl Niño/Southern Oscillation. In
addition, the eddies can masquerade as Rossby wave within a limited
latitude, which directly related to the oceanic basin, the local
characteristics of eddies and the period of masqueraded waves. Based on
the conservation of potential vorticity, the transient adjustment of
ocean circulation to response of the large-scale atmospheric forcing
from Rossby waves turn to ubiquitous vortices at increase of latitude.