Abstract
A substantial portion of ocean eddies, especially small ones, may be missed due to insufficient spatial or temporal sampling by satellite altimetry. In order to illustrate the influence of spatial resolution on eddy detection, this study provides a comparison of eddy identification, tracking, and analysis between two sets of merged altimeter data with spatial resolutions of 1/4° and 1/8°. One main study area (the Mediterranean Sea), and three confirmatory areas (the South-China Sea, the North-West Pacific, and the South-East Pacific) are chosen. The results show that the number and density of eddies captured by the 1/8° data are about twice as much as those captured by the 1/4° data, while the ratios of corresponding eddy parameters, i.e., radius, amplitude, (eddy kinetic energy (EKE)) are about 0.6–0.8 (1.3) for the two datasets (1/8° ÷ 1/4°). Long-term eddy tracking (1993–2018) is conducted in the Mediterranean Sea, indicating that the improvement in spatial resolution will increase the observed values of both the lifetime and the propagation distance of robust eddies. The number of eddies identified using the 1/4° data only accounts for ~30% to 60% of those identified using the 1/8° data. However, for eddies that can be detected using the two datasets, ~5% to 10% present errors (i.e., confusion). In comparison between the four regions, we find that for the enclosed seas with complex conditions, the increase in spatial resolution may lead to more significant improvements in the efficiency and accuracy of eddy detection.
Highlights
Ocean eddy is a general term for the rotational motion of seawater with a scale smaller than a Rossby wave, which is controlled by the geostrophic potential vorticity conservation equation [1]
We analyze the impact of the resolution improvement of satellite altimetry data on eddy research
Four sea areas: the Mediterranean Sea, the South-China Sea, the North-West Pacific, and the South-East Pacific are selected for the study
Summary
Ocean eddy is a general term for the rotational motion of seawater with a scale smaller than a Rossby wave, which is controlled by the (quasi) geostrophic potential vorticity conservation equation [1]. They are broadly distributed in the ocean and play a significant role in the transportation and mixing of physical and biological properties [1,2,3]. The momentum transport resulting from them has effectively impacted many features of the circulation, large-scale seawater distribution, and ecosystem characteristics of the global ocean [5,6,7,8,9,10,11]. The study of ocean eddies has become a core theme of modern oceanography over the past few decades [16]
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