How Mesoscale Eddies Masquerade as Rossby Waves in Merged Altimetric Products

Abstract

The existence of Rossby waves is due to the latitudinal variation of planetary vorticity and was predicted by Carl-Gustaf Rossby in the 1930s (Dickinson, 1978. According to linear theory, there is an infinite number of normal modes of Rossby waves in a continuously stratified ocean, found by solving an eigenvalue problem and which are ordered by decreasing westward phase speeds (Gill, 1982;Pedlosky, 1986). In particular, long, first baroclinic mode Rossby waves play an important role in the local climate variability and are the primary focus of this study. These nondispersive long waves can transport energy (potential and kinetic) westward and help maintain mid-latitude gyres and intensify western boundary currents (Polito & Liu, 2003). As small sea level anomaly (SLA) variations (∼10 cm), slow westward propagation speeds (∼10 cm/s), and long wavelengths (∼1,000 km) characterize Rossby waves, the complete picture of Rossby waves in the global ocean has been difficult to observe (Chelton & Schlax, 1996. Hereafter CS96). The existence and nature of Rossby waves in patchy temperature data required careful attention, and theoretical predictions have been waiting sufficient satellite altimetric data for unequivocal confirmation (Killworth et al., 1997).