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Atmospheric and Oceanic Physics

New submissions

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New submissions for Thu, 25 May 17

[1]  arXiv:1705.08487 [pdf, other]
Title: Transport by Lagrangian Vortices in the Eastern Pacific
Subjects: Atmospheric and Oceanic Physics (physics.ao-ph)

Rotationally coherent Lagrangian vortices (RCLVs) are identified from satellite-derived surface geostrophic velocities in the Eastern Pacific (180$^\circ$-130$^\circ$ W) using the objective (frame-invariant) finite-time Lagrangian-coherent-structure detection method of Haller et al. (2016) based on the Lagrangian-averaged vorticity deviation. RCLVs are identified for 30, 90, and 270 day intervals over the entire satellite dataset, beginning in 1993. In contrast to structures identified using Eulerian eddy-tracking methods, the RCLVs maintain material coherence over the specified time intervals, making them suitable for material transport estimates. Statistics of RCLVs are compared to statistics of eddies identified from sea-surface height (SSH) by Chelton et al. 2011. RCLVs and SSH eddies are found to propagate westward at similar speeds at each latitude, consistent with the Rossby wave dispersion relation. However, RCLVs are uniformly smaller and shorter-lived than SSH eddies. A coherent eddy diffusivity is derived to quantify the contribution of RCLVs to meridional transport; it is found that RCLVs contribute less than 1% to net meridional dispersion and diffusion in this sector, implying that eddy transport of tracers is mostly due to incoherent motions, such as swirling and filamentation outside of the eddy cores, rather than coherent meridional translation of eddies themselves. These findings call into question prior estimates of coherent eddy transport based on Eulerian eddy identification methods.

[2]  arXiv:1705.08547 [pdf, other]
Title: SPH Modeling of Short-crested Waves
Comments: Conference Paper, Proceedings of 12th International SPHERIC Workshop, June 13-15, 2017. Ourense, Spain
Subjects: Atmospheric and Oceanic Physics (physics.ao-ph)

This study investigates short-crested wave breaking over a planar beach by using the mesh-free Smoothed Particle Hydrodynamics model, GPUSPH. The short-crested waves are created by generating intersecting wave trains in a numerical wave basin. We examine the influence of beach slope, incident wave height, and incident wave angle on the generated short-crested waves. Short-crested wave breaking over a steeper beach generates stronger rip currents, and larger circulation cells in front of the beach. Intersecting wave trains with a larger incident wave height drive a more complicated short-crested wave field including isolated breakers and wave amplitude diffraction. Nearshore circulation induced by short-crested wave breaking is greatly influenced by the incident wave angle (or the rip current spacing). There is no secondary circulation cell between the nodal line and the antinodal line if the rip current spacing is narrow. However, there are multiple secondary circulation cells observed when the rip current spacing is relatively large.

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