Steepest ascent low/non-low frequency ratio in empirical mode decomposition to separate deterministic and stochastic velocities from a single Lagrangian drifter
Chu, Peter C.
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SOund Fixing And Ranging (RAFOS) floats deployed by the Naval Postgraduate School (NPS) in 4 the California Current system from 1992 to 2001 at depth between 150 and 600 m (http://www.oc.nps.edu/ 5 npsRAFOS/) are used to study 2-D turbulent characteristics. Each drifter trajectory is adaptively decomposed 6 using the empirical mode decomposition (EMD) into a series of intrinsic mode functions (IMFs) with corre- 7 sponding specific scale for each IMF. A new steepest ascent low/non-low-frequency ratio is proposed in this 8 paper to separate a Lagrangian trajectory into low-frequency (nondiffusive, i.e., deterministic) and high- 9 frequency (diffusive, i.e., stochastic) components. The 2-D turbulent (or called eddy) diffusion coefficients 10 are calculated on the base of the classical turbulent diffusion with mixing length theory from stochastic 11 component of a single drifter. Statistical characteristics of the calculated 2-D turbulence length scale, 12 strength, and diffusion coefficients from the NPS RAFOS data are presented with the mean values (over the 13 whole drifters) of the 2-D diffusion coefficients comparable to the commonly used diffusivity tensor method.
The article of record as published may be found at http://dx.doi.org/10.1002/2017JC013500