How Mesoscale Eddies Masquerade as Rossby Waves in Merged Altimetric Products

Abstract

AbstractWave‐like signals formed by mesoscale‐eddy propagation, in particular, overlap with actual waves, resulting in Rossby waves being misidentified or overestimated. This study revisited the puzzle of wave‐eddy aliasing in state‐of‐the‐art altimetric products, with up to six altimetry satellites operating simultaneously after 2016. Spatiotemporal scales and westward‐propagating speeds are the primary factors in diagnosing a low‐latitude Rossby wave regime from a high‐latitude geostrophic turbulence regime, confirming the coexistence of Rossby waves and eddies in wave‐like components. Long‐lived westward‐propagating eddies (prevailing in oceans at latitudes 10°–40°) with weaker meridional deflection are good candidates for masquerading as Rossby waves. The focus here is therefore on the long, first baroclinic mode Rossby waves, which are quantified in several periodic bands by removing eddy signals. From 2016 to 2020, energetic biannual Rossby waves can explain more than 10% of observed sea level anomalies at latitudes equatorward of ±25°, ±20°, and ±15° in the Pacific, Indian, and Atlantic Oceans, respectively. Numerical modeling results support similar assessments, indicating an intrinsic property of eddies masquerading as Rossby waves. This study provides a more accurate assessment of oceanic Rossby waves, which can deepen insight into the energy cascade of the geostrophic features and their dynamic effects on biogeochemical cycles.