The mission of Surface Water and Ocean Topography (SWOT) is scheduled to be launchedin 2022, and global ocean eddies with radius scales of larger than 10 km are expected to be observedfrom space. However, there are still open questions about the capability of SWOT to detect oceaneddies. Based on ocean model data and SWOT orbit, this study simulates along-track observationof SWOT. Two eddy datasets are derived from simulated observation data via mapping and eddyidentification procedures, one of which includes SWOT errors and the other does not. The thirdeddy dataset is generated from the original model data. Through comparing these three eddydatasets, it is found that 34% (40%) eddies are lost due to insufficient temporal sampling and errorsin the Kuroshio Extension (South China Sea) region, and numerous artifact eddies are generated.To further explain the influence of SWOT errors on smaller-scale eddies, two eddies (a cyclonic eddyand an anticyclonic eddy) with the radius of about 10 km are repeatedly observed 100 times usingthe SWOT-simulator. The cyclonic eddy with larger amplitude has been detected 84 times, whilethe anticyclonic eddy is visible 76 times. Therefore, the influence of the SWOT sampling and errorson ocean eddy observation is revealed by the results of these observing system simulationexperiments (OSSEs).
The propagation pathways of mesoscale eddies have an essential impact on the meridional transport of freshwater, carbon, nutrients, and other tracers. However, existing methods have limitations in exactly expressing their major propagation pathways. To tackle this problem, a direction‐based spatial clustering algorithm for the trajectory is proposed according to the partition‐and‐group framework. The idea is to extract the major eddy channels quantitatively, thus effectively representing the eddy trajectories with similar propagation pathways in a given spatial distance and direction, from the eddy identification and tracking datasets obtained by satellite altimetry spanning nearly 20 years in the Southern Ocean. The major eddy channels of the Southern Ocean are more geographically correlated rather than determined by polarity (anticyclonic eddies (AEs) and cyclonic eddies (CEs)). Importantly, the main axes of zonal propagation for eddy channels are extracted in this study. In the area north of 45°S (30°S–45°S), the zonal propagation (both for AEs and CEs) is intrinsically westward along ∼42°S ± 2° (main axes). While in those south of 45°S (45°S–80°S), it is reversed to eastward, propagating zonally along ∼56°S ± 2° (main axes) and obviously showing a gyre pattern. The bottom topography significantly effects on the propagation pathways of eddy channels in the Southern Ocean. Mainly, their meridional propagation pathways are pronouncedly steered by the shape of oceanic ridges around isobath −3900m (AEs for −3,877 m, CEs for −3,922 m).
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