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3 - Favorite trajectories
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- By Amy Bower, Department of Physical Oceanography, Woods Hole Oceanographic Institute, Woods Hole, Massachusetts, USA, Heather Furey, Department of Physical Oceanography, Woods Hole Oceanographic Institute, Woods Hole, Massachusetts, USA, Senya Grodsky, University of Maryland, College Park, Maryland, USA, Jim Carton, University of Maryland, College Park, Maryland, USA, Luca R. Centurioni, Scripps Institution of Oceanography, La Jolla, California, USA, Pearn P. Niiler, Scripps Institution of Oceanography, La Jolla, California, USA, Yoo Yin Kim, Scripps Institution of Oceanography La Jolla California USA, Dong-Kyu Lee, Busan National University, Busan, South Korea, Vitalii A. Sheremet, University of Rhode Island, Kingston, Rhode Island, USA, Newell Garfield, San Francisco State University, Tiburon, California, USA, Curtis A. Collins, Department of Oceanography, Naval Postgraduate School, Monterey, California, USA, Thomas A. Rago, Department of Oceanography, Naval Postgraduate School, Monterey, California, USA, Vassiliki Kourafalou, Rosenstiel School of Marine and Atmospheric Science, University of Miami, Miami, Florida, USA, Elizabeth Williams, Rosenstiel School of Marine and Atmospheric Science, University of Miami, Miami, Florida, USA, Thomas Lee, Rosenstiel School of Marine and Atmospheric Science, University of Miami, Miami, Florida, USA, Matthias Lankhorst, Leibniz-Institut für Meereswissenschaften (IFM-GEOMAR), Kiel, Germany, Walter Zenk, Leibniz-Institut für Meereswissenschaften (IFM-GEOMAR), Kiel, Germany, Arthur J. Mariano, Rosenstiel School of Marine and Atmospheric Science, University of Miami, Miami, Florida, USA, Edward H. Ryan, Rosenstiel School of Marine and Atmospheric Science, University of Miami, Miami, Florida, USA, Pierre-Marie Poulain, Istituto Nazionale di Oceanografia e di Geofisica Sperimentale (OGS), Trieste, Italy, Hedinn Valdimarsson, Marine Research Institute, Reykjavik, Iceland, Svend-Aage Malmberg, Marine Research Institute, Reykjavik, Iceland
- Edited by Annalisa Griffa, University of Miami, A. D. Kirwan, Jr., University of Delaware, Arthur J. Mariano, University of Miami, Tamay Özgökmen, University of Miami, H. Thomas Rossby, University of Rhode Island
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- Book:
- Lagrangian Analysis and Prediction of Coastal and Ocean Dynamics
- Published online:
- 07 September 2009
- Print publication:
- 10 May 2007, pp 68-88
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Summary
In this chapter, a collection of “favorite trajectories” from various authors are presented.
While Lagrangian data analysis uses an extensive array of sophisticated tools, including classical statistics, dynamical system theory, stochastic modelling, assimilation techniques, and many others, visual inspection of individual trajectories still plays an important role, providing the first and often fundamental glimpse of the underlying dynamics. Often, for Lagrangian investigators, looking at trajectories gives the first intuition, then leading to the use of sophisticated and appropriate analysis. Trajectories tell the story of the journey of drifters and floats, and these stories are often complex and fascinating.
In the following sections, a number of investigators take us in the various world oceans, including Atlantic, Pacific and regional Seas, from the Poles to the Tropics, telling us the stories of their favorite trajectories and giving us their intuition and physical insights.
Mesoscale eddies in the Red Sea outflow region
In 2001–2002, 50 RAFOS floats were released at the core depth (∼ 650 m) of Red Sea Outflow Water (RSOW) in the Gulf of Aden (northwestern Indian Ocean) as part of the Red Sea Outflow Experiment (REDSOX). The objective was to determine how warm, saline RSOW spreads from its source at the southern end of Bab al Mandeb Strait to the open Indian Ocean. Our hypothesis was that either boundary undercurrents or submesoscale coherent vortices (SCVs like Meddies, but here called “Reddies”) were the main transport mechanisms for RSOW.
Laboratory experiments with tilted convective plumes on a centrifuge: a finite angle between the buoyancy force and the axis of rotation
- VITALII A. SHEREMET
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- Journal:
- Journal of Fluid Mechanics / Volume 506 / 10 May 2004
- Published online by Cambridge University Press:
- 28 April 2004, pp. 217-244
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The effect of both vertical and horizontal components of the Earth's rotation on plumes during deep convection in the ocean is studied. In the laboratory, the misalignment, characterized by the angle $\alpha$, between the buoyancy force (‘effective’ free-fall acceleration ${\bm g}_e$) and the rotation axis ${\bm \Omega}$ is produced by using the centrifugal force: an experimental tank was placed at a large distance from the centre of the turntable. The mathematical analogy between the laboratory model and the oceanic environment is presented. For $\alpha\,{=}\,30^\circ$, a number of laboratory experiments spanning a wide range of the buoyancy flux parameter, and correspondingly Reynolds number, is used to illustrate the development of the convective plume from a point source in regimes ranging from weakly to highly turbulent. New features of the flow, as compared to $\alpha\,{=}\,0$, are documented and explained.
The incoming heavier dyed fluid jet disintegrates into fast-sinking coherent blobs (in a low-Reynolds-number regime) or turbulent billows (in a high-Reynolds-number regime) and a more diffuse cloud of highly diluted dyed water. An analysis of the forces acting on an ellipsoid moving in a rotating fluid with the main balance including the buoyancy, Coriolis forces, and the hydrodynamic reaction due to generation of inertial waves correctly predicts the trajectory of a descending blob. It also explains the tendency of the plume to develop in the direction intermediate between ${\bm g}_e$ and ${\bm \Omega}$ and to shift ‘eastward’ (lagging the rotation of the centrifuge) if the plume is envisaged as an ensemble of blobs.
The stretching of the highly diluted dyed water along the absolute vorticity tubes with simultaneous shearing by horizontal quasi-two-dimensional flow produces conspicuous tilted structures or tilted Taylor ‘ink walls’. The misalignment between ${\bm g}_e$ and ${\bm \Omega}$ enhances the turbulent mixing and development of tilted structures by breaking the symmetry and producing motions directed away from the rotation axis.
We argue that the conditions at the sites of ocean deep convection are favourable for the development of tilted structures because of the smallness of the Rossby number and an extreme homogenization of the mixed layer. We hypothesize that the homogenized sublayers observed within actively convecting regions in the ocean may not be horizontal, but in fact analogous to the tilted ‘ink walls’ observed in the laboratory experiments and that they represent the internal structure of a plume on horizontal scales smaller than its depth.