scholarly journals Angular Momentum Eddy Detection and Tracking Algorithm (AMEDA) and Its Application to Coastal Eddy Formation

2018 ◽  
Vol 35 (4) ◽  
pp. 739-762 ◽  
Author(s):  
Briac Le Vu ◽  
Alexandre Stegner ◽  
Thomas Arsouze
Keyword(s):  
Angular Momentum ◽  
Velocity Field ◽  
Dynamical Evolution ◽  
Mesoscale Eddies ◽  
Velocity Fields ◽  
Tracking Algorithm ◽  
Fine Tuning ◽  
Surface Velocity ◽  
Detection And Tracking ◽  
Eddy Detection

AbstractAutomated methods are important for the identification of mesoscale eddies in the large volume of oceanic data provided by altimetric measurements and numerical simulations. This paper presents an optimized algorithm for detecting and tracking eddies from two-dimensional velocity fields. This eddy identification uses a hybrid methodology based on physical parameters and geometrical properties of the velocity field, and it can be applied to various fields having different spatial resolutions without a specific fine-tuning of the parameters. The efficiency and the robustness of the angular momentum eddy detection and tracking algorithm (AMEDA) was tested with three different types of input data: the 1/8° Archiving, Validation, and Interpretation of Satellite Oceanographic Data (AVISO) geostrophic velocity fields available for the Mediterranean Sea; the output of the idealized Regional Ocean Modeling System numerical model; and the surface velocity field obtained from particle imagery on a rotating tank experiment. All these datasets describe the dynamical evolution of mesoscale eddies generated by the instability of a coastal current. The main advantages of AMEDA are as follows: the algorithm is robust to the grid resolution, it uses a minimal number of tunable parameters, the dynamical features of the detected eddies are quantified, and the tracking procedure identifies the merging and splitting events. The proposed method provides a complete dynamical evolution of the detected eddies during their lifetime. This allows for identifying precisely the formation areas of long-lived eddies, the region where eddy splitting or merging occurs frequently, and the interaction between eddies and oceanic currents.

scholarly journals A Vector Geometry–Based Eddy Detection Algorithm and Its Application to a High-Resolution Numerical Model Product and High-Frequency Radar Surface Velocities in the Southern California Bight

2010 ◽  
Vol 27 (3) ◽  
pp. 564-579 ◽  
Author(s):  
Francesco Nencioli ◽  
Changming Dong ◽  
Tommy Dickey ◽  
Libe Washburn ◽  
James C. McWilliams
Keyword(s):  
High Resolution ◽  
Numerical Model ◽  
High Frequency ◽  
Southern California ◽  
Velocity Fields ◽  
Southern California Bight ◽  
Surface Velocity ◽  
Physical Parameters ◽  
High Frequency Radar ◽  
Eddy Detection

Abstract Automated eddy detection methods are fundamental tools to analyze eddy activity from the large datasets derived from satellite measurements and numerical model simulations. Existing methods are either based on the distribution of physical parameters usually computed from velocity derivatives or on the geometry of velocity streamlines around minima or maxima of sea level anomaly. A new algorithm was developed based exclusively on the geometry of the velocity vectors. Four constraints characterizing the spatial distribution of the velocity vectors around eddy centers were derived from the general features associated with velocity fields in the presence of eddies. The grid points in the domain for which these four constraints are satisfied are detected as eddy centers. Eddy sizes are computed from closed contours of the streamfunction field, and eddy tracks are retrieved by comparing the distribution of eddy centers at successive time steps. The results were validated against manually derived eddy fields. Two parameters in the algorithm can be modified by the users to optimize its performance. The algorithm is applied to both a high-resolution model product and high-frequency radar surface velocity fields in the Southern California Bight.

scholarly journals Detecting and tracking eddies in oceanic flow fields: a Lagrangian descriptor based on the modulus of vorticity

2016 ◽  
Vol 23 (4) ◽  
pp. 159-173 ◽  
Author(s):  
Rahel Vortmeyer-Kley ◽  
Ulf Gräwe ◽  
Ulrike Feudel
Keyword(s):  
Velocity Field ◽  
Baltic Sea ◽  
Local Maximum ◽  
Velocity Fields ◽  
Vortex Street ◽  
Suitable Method ◽  
Convection Flow ◽  
Hyperbolic Trajectories ◽  
Synthetic Vortex ◽  
Eddy Detection

Abstract. Since eddies play a major role in the dynamics of oceanic flows, it is of great interest to detect them and gain information about their tracks, their lifetimes and their shapes. We present a Lagrangian descriptor based on the modulus of vorticity to construct an eddy tracking tool. In our approach we denote an eddy as a rotating region in the flow possessing an eddy core corresponding to a local maximum of the Lagrangian descriptor and enclosed by pieces of manifolds of distinguished hyperbolic trajectories (eddy boundary). We test the performance of the eddy tracking tool based on this Lagrangian descriptor using an convection flow of four eddies, a synthetic vortex street and a velocity field of the western Baltic Sea. The results for eddy lifetime and eddy shape are compared to the results obtained with the Okubo–Weiss parameter, the modulus of vorticity and an eddy tracking tool used in oceanography. We show that the vorticity-based Lagrangian descriptor estimates lifetimes closer to the analytical results than any other method. Furthermore we demonstrate that eddy tracking based on this descriptor is robust with respect to certain types of noise, which makes it a suitable method for eddy detection in velocity fields obtained from observation.

scholarly journals Structure and Dynamics of the Ras al Hadd Oceanic Dipole in the Arabian Sea

Oceans ◽  
2021 ◽  
Vol 2 (1) ◽  
pp. 105-125
Author(s):  
Adam Ayouche ◽  
Charly De Marez ◽  
Mathieu Morvan ◽  
Pierre L’Hegaret ◽  
Xavier Carton ◽  
...  
Keyword(s):  
Process Model ◽  
Model Simulation ◽  
Ocean Model ◽  
Tracking Algorithm ◽  
Detection And Tracking ◽  
Hybrid Coordinate Ocean Model ◽  
Persian Gulf Water ◽  
The Persian Gulf ◽  
Water Outflow ◽  
Eddy Detection

The Ras al Hadd oceanic dipole is a recurrent association of a cyclone (to the northeast) and of an anticyclone (to the southwest), which forms in summer and breaks up at the end of autumn. It lies near the Ras al Hadd cape, southeast of the Arabian peninsula. Its size is on the order of 100 km. Along the axis of this dipole flows an intense jet, the Ras al Had jet. Using altimetric data and an eddy detection and tracking algorithm (AMEDA: Angular Momentum Eddy Detection and tracking Algorithm), we describe the life cycle of this oceanic dipole over a year (2014–2015). We also use the results of a numerical model (HYCOM, the HYbrid Coordinate Ocean Model) simulation, and hydrological data from ARGO profilers, to characterize the vertical structure of the two eddies composing the dipole, and their variability over a 15 year period. We show that (1) before the dipole is formed, the two eddies that will compose it, come from different locations to join near Ras al Hadd, (2) the dipole remains near Ras al Hadd during summer and fall while the wind stress (due to the summer monsoon wind) intensifies the cyclone, (3) both the anticyclone and the cyclone reach the depth of the Persian Gulf Water outflow, and (4) their horizontal radial velocity profile is often close to Gaussian but it can vary as the dipole interacts with neighboring eddies. As a conclusion, further work with a process model is recommended to quantify the interaction of this dipole with surrounding eddies and with the atmosphere.

scholarly journals Experimental Validation of Falling Liquid Film Models: Velocity Assumption and Velocity Field Comparison

Polymers ◽  
2021 ◽  
Vol 13 (8) ◽  
pp. 1205
Author(s):  
Ruiqi Wang ◽  
Riqiang Duan ◽  
Haijun Jia
Keyword(s):  
Experimental Data ◽  
Particle Image Velocimetry ◽  
Velocity Field ◽  
Experimental Validation ◽  
Particle Image ◽  
Velocity Fields ◽  
Number Range ◽  
Comparison Results ◽  
Image Velocimetry ◽  
Experimental Particle

This publication focuses on the experimental validation of film models by comparing constructed and experimental velocity fields based on model and elementary experimental data. The film experiment covers Kapitza numbers Ka = 278.8 and Ka = 4538.6, a Reynolds number range of 1.6–52, and disturbance frequencies of 0, 2, 5, and 7 Hz. Compared to previous publications, the applied methodology has boundary identification procedures that are more refined and provide additional adaptive particle image velocimetry (PIV) method access to synthetic particle images. The experimental method was validated with a comparison with experimental particle image velocimetry and planar laser induced fluorescence (PIV/PLIF) results, Nusselt’s theoretical prediction, and experimental particle tracking velocimetry (PTV) results of flat steady cases, and a good continuity equation reproduction of transient cases proves the method’s fidelity. The velocity fields are reconstructed based on different film flow model velocity profile assumptions such as experimental film thickness, flow rates, and their derivatives, providing a validation method of film model by comparison between reconstructed velocity experimental data and experimental velocity data. The comparison results show that the first-order weighted residual model (WRM) and regularized model (RM) are very similar, although they may fail to predict the velocity field in rapidly changing zones such as the front of the main hump and the first capillary wave troughs.

Applications for a people detection and tracking algorithm using a time-of-flight camera

2014 ◽  
Vol 75 (17) ◽  
pp. 10769-10786 ◽  
Author(s):  
Carsten Stahlschmidt ◽  
Alexandros Gavriilidis ◽  
Jörg Velten ◽  
Anton Kummert
Keyword(s):  
Time Of Flight ◽  
Tracking Algorithm ◽  
People Detection ◽  
Detection And Tracking
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