Investigating mesoscale eddy characteristics in the Luzon Strait region using altimetry

2021 ◽  
Author(s):  
Corinne B. Trott ◽  
E. Joseph Metzger ◽  
Zhitao Yu
Keyword(s):  
Mesoscale Eddy ◽  
Luzon Strait ◽  
Eddy Characteristics

scholarly journals Features of Intraseasonal Variability Observed in the Upper-Layer Current in the Northern South China Sea

2021 ◽  
Vol 8 ◽  
Author(s):  
Wen Xu ◽  
Yeqiang Shu ◽  
Dongxiao Wang ◽  
Ju Chen ◽  
Jinghong Wang ◽  
...  
Keyword(s):  
South China Sea ◽  
South China ◽  
Northern South China Sea ◽  
Intraseasonal Variability ◽  
Mesoscale Eddy ◽  
Luzon Strait ◽  
Altimeter Data ◽  
China Sea ◽  
Spatial Differences ◽  
Long Time

This study reveals the features of the strong intraseasonal variability (ISV) of the upper-layer current in the northern South China Sea (NSCS) based on four long-time mooring observations and altimeter data. The ISV of the upper-layer current in the NSCS consists of two dominant periods of 10–65 days and 65–110 days. The ISV with period of 10–65 days is much strong in the Luzon Strait and decays rapidly westward along the slope. The ISV with the period of 65–110 days is relatively strong along the slope with two high cores at 115 and 119°E, whereas it is weak in the Luzon Strait. The 10–65-day ISV can propagate directly from the western Pacific into the NSCS for most of the time. However, due to its long wavelength, the 65–110-day ISV propagates into the NSCS indirectly, possibly similar to the wave diffraction phenomenon. The spatial differences between the two main frequency bands are primarily due to the baroclinic and barotropic instabilities. The spatial distribution of the upper-layer ISV is closely associated with the mesoscale eddy radius of the NSCS. The eddy radius is directly proportional to the strength of 65–110-day ISV, but it is inversely proportional to the strength of 10–65-day ISV.

scholarly journals Topographic Influence on Baroclinic Instability and the Mesoscale Eddy Field in the Northern North Atlantic Ocean and the Nordic Seas

2018 ◽  
Vol 48 (11) ◽  
pp. 2593-2607 ◽  
Author(s):  
Marta Trodahl ◽  
Pål Erik Isachsen
Keyword(s):  
North Atlantic ◽  
Bottom Topography ◽  
Baroclinic Instability ◽  
Mesoscale Eddy ◽  
Ocean Model ◽  
Topographic Effects ◽  
Nordic Seas ◽  
Boundary Currents ◽  
Eddy Characteristics ◽  
Eddy Field

AbstractA weak planetary vorticity gradient and weak density stratification in the northern North Atlantic and Nordic seas lead to time-mean currents that are strongly guided by bottom topography. The topographic steering sets up distinct boundary currents with strong property fronts that are prone to both baroclinic and barotropic instability. These instability processes generate a macroturbulent eddy field that spreads buoyancy and other tracers out from the boundary currents and into the deep basins. In this paper we investigate the particular role played by baroclinic instability in generating the observed eddy field, comparing predictions from linear stability calculations with diagnostics from a nonlinear eddy-permitting ocean model hindcast. We also look into how the bottom topography impacts instability itself. The calculations suggest that baroclinic instability is a consistent source of the eddy field but that topographic potential vorticity gradients impact unstable growth significantly. We also observe systematic topographic effects on finite-amplitude eddy characteristics, including a general suppression of length scales over the continental slopes. Investigation of the vertical structure of unstable modes reveal that Eady theory, even when modified to account for a bottom slope, is unfit as a lowest-order model for the dynamics taking place in these ocean regions.

Numerical study on the interactions between the Kuroshio current in the Luzon Strait and a mesoscale eddy

2017 ◽  
Vol 67 (3-4) ◽  
pp. 369-381 ◽  
Author(s):  
Yi-Chun Kuo ◽  
Ching-Sheng Chern ◽  
Zhe-Wen Zheng
Keyword(s):  
Numerical Study ◽  
Mesoscale Eddy ◽  
Kuroshio Current ◽  
Luzon Strait ◽  
The Kuroshio

Mesoscale eddy characteristics in the Labrador Sea from observations and a 1/60° numerical model

2020 ◽  
Author(s):  
Arne Bendinger ◽  
Johannes Karstensen ◽  
Julien Le Sommer ◽  
Aurélie Albert ◽  
Fehmi Dilmahamod
Keyword(s):  
Solid Body ◽  
Inner Core ◽  
Velocity Structure ◽  
Mesoscale Eddy ◽  
Skill Assessment ◽  
Labrador Sea ◽  
Body Rotation ◽  
Data Set ◽  
Solid Body Rotation ◽  
Eddy Characteristics

<p>Mesoscale eddies play an important role in lateral property fluxes. Observational studies often use sea level anomaly maps from satellite altimetry to estimate eddy statistics (incl. eddy kinetic energy). Recent findings suggest that altimetry derived eddy characteristics may suffer from the low spatial resolution of past and current satellite-tracks in high-latitude oceans associated with small Rossby radii. Here we present results of an eddy reconstruction based on a nonlinear damping Gauss-Newton optimisation algorithm using ship based current profiler observations from two research expeditions in the Labrador Sea in 2014 and 2016. Overall we detect 14 eddies with radii ranging from 7 to 35 km.</p><p>In order to verify the skill of the reconstruction we used the submesoscale permitting NATL60 model (1/60°) as a reference data set. Spectral analysis of the horizontal velocity implies that the mesoscale regime is well represented in NATL60 compared with the observations. The submesoscale regime in the model spectra shows deviations to the observations at scales smaller than 10km near the ocean surface. The representation of the submesoscale flow further decreases in the model with increasing depth.</p><p>By subsampling the NATL60 model velocities along artificial ship tracks, applying our eddy reconstruction algorithm, and comparing the results with the full model field, a skill assessment of the reconstruction is done. We show that the reconstruction of the eddy characteristics can be affected by the location of the ship track through the velocity field.</p><p>In comparison with the observed eddies the NATL60 eddies have smaller radii and higher azimuthal velocities and thus are more nonlinear. The inner core velocity structure for observations and NATL60 suggests solid body rotation for 2/3 of the radius. The maximum azimuthal velocity may deviate by up to 50% from solid body rotation.</p><p>The seasonality of the submesoscale regime can be seen in the data as the power spectrum is reduced from spring to summer in both the ship-based measurements and model.</p>

Three mesoscale eddy detection and tracking methods: Assessment for the South China Sea

2020 ◽  
Author(s):  
Tao Xing ◽  
Yikai Yang
Keyword(s):  
South China Sea ◽  
South China ◽  
Mesoscale Eddy ◽  
The South China Sea ◽  
The South ◽  
China Sea ◽  
Advantages And Disadvantages ◽  
Detection And Tracking ◽  
Eddy Characteristics ◽  
Eddy Detection

AbstractComplex topography and the Kuroshio eddy shedding process produce active mesoscale eddy activity in the South China Sea (SCS). Three eddy detection and tracking methods, the Okubo-Weiss (O-W), Vector-Geometry (V-G), and Winding-Angle (W-A) algorithms, have been widely applied for eddy identification. This study provides a comprehensive assessment of the O-W, V-G and W-A methods in the SCS, including their detection, statistical analysis, and tracking capabilities. The mean successful detection rates (SDRs) of the O-W, V-G and W-A methods are 51.9%, 56.8% and 61.4%, respectively. The O-W and V-G methods preferentially detect eddies with medium radii (1/2°-1°), while the W-A method is tend to be larger radii (>1°). The V-G method identifies an excessive number of weak (radius<1/3°) eddy-like structures in the SCS, accounting for 48.2% of the total eddy number. The highest mean excessive detection rate (EDR) of the V-G method biases the data on eddy number, probability and propagation direction. With the lowest mean successful tracking rate (STR), the O-W method might not be suitable for tracking long-lived eddies in the SCS. The V-G method performs well regarding the over-tracking issue and has the lowest mean questionable tracking rate (QTR) of 1.1%. Among the three methods, the W-A method tracks eddies most accurately, with the highest mean STR of 80.6%. Overall, the W-A method produces reasonable statistical eddy characteristics and eddy tracking results. Each method has advantages and disadvantages, and researchers should choose wisely according to their needs.

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