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Nonlinear Processes in Geophysics An interactive open-access journal of the European Geosciences Union

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Nonlin. Processes Geophys., 25, 267-278, 2018
https://doi.org/10.5194/npg-25-267-2018
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.
Research article
04 Apr 2018
Connection between encounter volume and diffusivity in geophysical flows
Irina I. Rypina1, Stefan G. Llewellyn Smith2, and Larry J. Pratt1 1Physical Oceanography Department, Woods Hole Oceanographic Institution, 266 Woods Hole Rd., Woods Hole, MA 02543, USA
2Department of Mechanical and Aerospace Engineering, Jacobs School of Engineering and Scripps Institution of Oceanography, UCSD, 9500 Gilman Dr., La Jolla, CA 92093-0411, USA
Abstract. Trajectory encounter volume – the volume of fluid that passes close to a reference fluid parcel over some time interval – has been recently introduced as a measure of mixing potential of a flow. Diffusivity is the most commonly used characteristic of turbulent diffusion. We derive the analytical relationship between the encounter volume and diffusivity under the assumption of an isotropic random walk, i.e., diffusive motion, in one and two dimensions. We apply the derived formulas to produce maps of encounter volume and the corresponding diffusivity in the Gulf Stream region of the North Atlantic based on satellite altimetry, and discuss the mixing properties of Gulf Stream rings. Advantages offered by the derived formula for estimating diffusivity from oceanographic data are discussed, as well as applications to other disciplines.
Citation: Rypina, I. I., Llewellyn Smith, S. G., and Pratt, L. J.: Connection between encounter volume and diffusivity in geophysical flows, Nonlin. Processes Geophys., 25, 267-278, https://doi.org/10.5194/npg-25-267-2018, 2018.
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Short summary
Trajectory encounter volume – the volume of fluid that passes close to a reference fluid parcel over some time interval – has been recently introduced as a measure of mixing potential of a flow. We derived the analytical relationship between the encounter volume and diffusivity, which is the most commonly used characteristic of turbulent eddy diffusion. When applied to the altimetric velocities in the Gulf Stream region, the method illuminated transport properties of the Gulf Stream rings.
Trajectory encounter volume – the volume of fluid that passes close to a reference fluid parcel...
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