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Arthur J. Mariano, Annalisa Griffa, Tamay M. Özgökmen, and Enrico Zambianchi

Abstract

The first Lagrangian Analysis and Predictability of Coastal and Ocean Dynamics (LAPCOD) meeting took place in Ischia, Italy, 2–6 October 2000. The material presented at LAPCOD 2000 indicated both a maturing of Lagrangian-based observing systems and the development of new analysis and assimilation techniques for Lagrangian data. This summary presents a review of the state-of-the-art technology in Lagrangian exploration of oceanic and coastal waters that was presented at the meeting.

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Massimo Cencini, Guglielmo Lacorata, Angelo Vulpiani, and Enrico Zambianchi

Abstract

Mixing and transport in correspondence of a meandering jet are investigated. The large-scale flow field is a kinematically assigned streamfunction. Two basic mixing mechanisms are considered separately and in combination: deterministic chaotic advection induced by a time dependence of the flow, and turbulent diffusion described by means of a stochastic model for particle motion.

Rather than looking at the details of particle trajectories, fluid exchange is studied in terms of Markovian approximations. The 2D physical space accessible to fluid particles is subdivided into regions characterized by different Lagrangian behavior. From the observed transitions between regions it is possible to derive a number of relevant quantities characterizing transport and mixing in the studied flow regime, such as residence times, meridional mixing, and correlation functions. These estimated quantities are compared to the corresponding ones resulting from the actual simulations. The outcome of the comparison suggests the possibility of describing in a satisfactory way at least some of the mixing properties of the system through the very simplified approach of a first-order Markovian approximation, whereas other properties exhibit memory patterns of higher order.

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Pierpaolo Falco, Annalisa Griffa, Pierre-Marie Poulain, and Enrico Zambianchi

Abstract

The surface transport properties in the Adriatic Sea, a semienclosed subbasin of the Mediterranean Sea, have been studied using a drifter dataset in the period December 1994–March 1996. Three main points have been addressed. First, the exchange between southern and northern regions and between deep and coastal areas have been studied, focusing on the role of topography. A significant cross-topography or cross-shelf exchange has been found, probably due to the direct wind forcing and to the influence of stratification that isolates the surface flow from bottom effects, especially in the open sea. Second, a Lagrangian transport model with parameters derived from the data has been implemented. Simulated particles have been compared with drifter data with positive results. The model is found to be able to reproduce reality with good approximation, except for a specific advective event during the late summer season. Finally, the residence timescale T, that is, the average time spent by a surface particle in the basin, has been estimated. Direct estimates from the data suggest T ≈ 70–90 days, but these values are biased due to the finite lifetime of the drifters. Model results have been used to estimate the bias, and they suggest a “true” value of T ≈ 200 days.

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