It was during the 1999 Liege Colloquium on, “Three-Dimensional Ocean Circulation: Lagrangian measurements and diagnostic analyses,” that a number of researchers started to discuss the idea of having a meeting centered on studying the ocean, the atmosphere, and marine biology from a Lagrangian viewpoint. At the time of this writing, three Lagrangian Analysis and Prediction of Coastal and Ocean Dynamics (LAPCOD) meetings have been held in (i) Ischia, Italy from October 2–6, 2000, (ii) Key Largo, FL, USA from December 12–16, 2002, and (iii) Lerici, Italy from June 13–17, 2005. The LAPCOD meetings bring together a diverse group of scientists for the purpose of exchanging ideas on the collection, analysis, modeling, and assimilation of coastal and oceanic (quasi-)Lagrangian data. The purpose of this chapter is to provide both a tutorial for readers who are not specialists, and a summary of the material presented at the LAPCOD meetings and in this book. Since this chapter summarizes the material presented at LAPCOD meetings and because of space constraints, many important Lagrangian-based studies are not detailed here and the chapter topics, listed in the next paragraph, are those topics that have been central to the LAPCOD meetings and this book. There are a number of unpublished results presented at LAPCOD 2005 discussed here and referenced by personal communication, hereafter pers. com.
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.
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