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2002 LAPCOD Meeting
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Oceanic turbulence and stochastic models from Lagrangian data: results in the North Atlantic Ocean.

Milena Veneziani(a), Annalisa Griffa(a,b), Andy Reynolds(c), Arthur J. Mariano(a)
(a)RSMAS/MPO, University of Miami, USA, (b)CNR, La Spezia, Italy, (c)Silsoe Research Institute, UK
cveneziani@rsmas.miami.edu

(Abstract received 10/10/2002 for session A)
ABSTRACT

The historical data set provided by 700 m acoustically-tracked floats (e.g. Owens, 1991) is analyzed in different regions of the north-western Atlantic Ocean. The goal is to characterize the main properties of mesoscale turbulence and to explore Lagrangian stochastic models capable of describing them. In the Gulf Stream extension and recirculation, the data results show significant oscillation time scales and oscillatory patterns both in the velocity autocovariance and crosscovariance functions. They are indicative of sub and super diffusive behaviors. The results also suggest a bimodal distribution of particle trajectories, a number of them being trapped inside highly energetic eddies (loopers), while the rest of the floats experience a poor looping behavior (no-loopers) (Richardson, 1991).

The data statistics are compared with statistics from different stochastic models. A 1-order model with spin is selected, which describes correctly the main observed features. The model couples the two velocity components through a 'spin' parameter, and it is therefore able to represent rotating coherent structures such as vortices and mesoscale eddies. The spin distribution is found to be approximately bimodal, with zero spin for the no-loopers and finite spin for the loopers. The observed super diffusive pattern results from the superposition of the two populations.

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2002 LAPCOD Meeting, Key Largo, Florida, December 12-16, 2000