한국해안·해양공학회논문집 (Journal of Korean Society of Coastal and Ocean Engineers)

  • 제27권2호
  • /
  • Pages.79-93
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  • 2015
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  • 1976-8192(pISSN)
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  • 2288-2227(eISSN)
한국해안·해양공학회 (Korean Society of Coastal and Ocean Engineers)
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수치모델 해상도가 중규모 와동 근처의 난류구조에 미치는 영향

Effect of Model Resolution on The Flow Structures Near Mesoscale Eddies

  • Chang, Yeon S. (Ocean Circulation and Climate Change Research Department, Korean Institute of Ocean Science and Technology) ;
  • Ahn, Kyungmo (School of Spatial Environment System Engineering, Handong Global University) ;
  • Park, Young-Gyu (Ocean Circulation and Climate Change Research Department, Korean Institute of Ocean Science and Technology)
  • 투고 : 2015.03.02
  • 심사 : 2015.03.25
  • 발행 : 2015.04.30
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초록

Gulf Stream 인근해역에서 해양 중규모 와동의 삼차원 구조분석을 HYCOM 수치모델을 사용하여 수행하였다. 시계방향 및 반시계 방향으로 회전하는 와동들의 구조를$1/12^{\circ}$와 $1/48^{\circ}$ 두개의 모델 해상도를 사용하여 비교하였다. 라그랑지안 모수인 Finite Size Lyapunov Exponent (FSLE) 와 Okubo-Weiss parameter(OW) 분포를 분석한 결과 표층의 와동구조가 수심 깊은 곳까지 영향을 미치는 것으로 나타났는데, 이는 와동에 의한 수평방향 해수운동이 수직방향 해수운동보다 크기 때문인 것으로 해석되었다. 고해상도 모델의 경우 와동근처에서 10 km 미만의 미세난류구조 들이 많이 발견되었으며, 이러한 미세난류구조들은 고해상도 모델의 와동근처에서 해수의 움직임을 저해상도 모델보다 불규칙하게 만드는 것으로 나타났다. 이러한 미세난류구조에 의한 해수의 불규칙한 움직임은 분산계수 (dispersion coefficient)에도 영향을 미치는데, 수평 분산계수의 경우 해수운동이 자유로운 고해상도 모델이 저해상도 모델보다 그 값이 더 크게 나타났다. 수직 분산계수의 값은 저해상도 모델에서 더 크게 나왔는데, 이는 와동의 경사진 궤도를 따라 움직이는 저해상도 모델의 해수운동이 수직 분산계수값을 증가시키기 때문인 것으로 들어났다. 상대 수직 분산계수의 경우 이러한 궤도의 영향이 줄어들기 때문에 해수의 수직운동을 측정하는데 있어 절대 수직 분산계수 보다 더 적합한 것으로 판명되었다.

Three-dimensional structures of large ocean rings in the Gulf Stream region are investigated using the HYbrid Coordinate Ocean Model (HYCOM). Numerically simulated flow structures around four selected cyclonic and anticyclonic rings are compared with two different horizontal resolutions: $1/12^{\circ}$ and $1/48^{\circ}$. The vertical distributions of Lagrangian Coherent Structures (LCSs) are analyzed using Finite Size Lyapunov Exponent (FSLE) and Okubo-Weiss parameters (OW). Curtain-shaped FSLE ridges are found in all four rings with extensions of surface ridges throughout the water columns, indicating that horizontal stirring is dominant over vertical motions. Near the high-resolution rings, many small-scale flow structures with size O(1~10) km are observed while these features are rarely found near the low-resolution rings. These small-scale structures affect the flow pattern around the rings as flow particles move more randomly in the high-resolution models. The dispersion rates are also affected by these small-scale structures as the relative horizontal dispersion coefficients are larger for the high-resolution models. The absolute vertical dispersion rates are, however, lower for the high-resolution models, because the particles tend to move along inclined eddy orbits when the resolution is low and this increases the magnitude of absolute vertical dispersion. Since relative vertical dispersion can reduce this effect from the orbital trajectories of particles, it gives a more reasonable magnitude range than absolute dispersion, and so is recommended in estimating vertical dispersion rates.

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참고문헌

  1. Allen, J.T. and Smeed, D.A. (1996). Potential vorticity and vertical velocity at the Iceland-Faroes Front. J. Phys. Oceanogr. 26(12), 2611-2634. https://doi.org/10.1175/1520-0485(1996)026<2611:PVAVVA>2.0.CO;2
  2. Artale, V., Boffetta, G., Celani, A., Cencini, M. and Vulpiani, A. (1997). Dispersion of passive tracers in closed basins: beyond the diffusion coefficients. Phys. Fluids, Vol. 9, 3162-3171. https://doi.org/10.1063/1.869433
  3. Aurell, E., Boffetta, G., Crisanti, A. Paladin, G. and Vulpiani, A. (1997). Predictability in the large: en extension of the concept of Lyapunov exponent. J. Phys. A, Vol. 30, 1-26. https://doi.org/10.1088/0305-4470/30/1/003
  4. Bettencourt, J.H., Lopez, C. and Hernandez-Garcia, E. (2012). Oceanic three-dimensional Lagrangian coherent structures: A study of a mesoscale eddy in the Benguela upwelling region. Ocean Modelling, Vol. 51, pp. 73-83. https://doi.org/10.1016/j.ocemod.2012.04.004
  5. Bettencourt, J.H., Lopez, C. and Hernandez-Garcia, E. (2013). Characterization of coherent structures in three-dimensional turbulent flows using the finite-size Lyapunov exponent. J. Phys. A: Math. Theor., Vol. 46(254022). https://doi.org/10.1088/1751-8113/46/25/254022
  6. Bleck, R., (2002). An oceanic general circulation model framed in hybrid isopycnic-Cartesian coordinates. Ocean Modelling, Vol. 4, 55-88. https://doi.org/10.1016/S1463-5003(01)00012-9
  7. Branicki, M. and Kirwan Jr., A.D. (2010). Stirring: The Eckart paradigm revisited. International Journal of Engineering Science, 48(11), 1027-1042. https://doi.org/10.1016/j.ijengsci.2010.08.003
  8. Branicki, M. and Wiggins, S. (2009). An adaptive method for computing invariant manifolds in non-autonomous, three-dimensional dynamical systems. Phys. D: Nonlinear Phenom. 238(16), 1625-1657. https://doi.org/10.1016/j.physd.2009.05.005
  9. Capet, X., McWilliams, J.C., Molemaker, M.J. and Shchepetkin, A. F. (2008). Mesoscale to submesoscale transition in the California current system. Part I: Flow structure, eddy, flux, and observational tests. J. Phys. Oceanogr. 38(1), 29-43. https://doi.org/10.1175/2007JPO3671.1
  10. Chang, Y.S. and Park, Y.-G. (2015). Temporal variation of flow properties of a mesoscale ocean eddy collided with another mesoscale eddy in the Gulf Stream region using Hybrid Coordinate Ocean Model (HYCOM). Ocean Science J. submitted
  11. Chang, Y.S., Garraffo, Z.D., Peters, H. and Ozgokmen, T.M. (2009). Pathways of Nordic overflows from climate model scale and eddy resolving simulations. Ocean Modelling, Vol. 29, 66-84. https://doi.org/10.1016/j.ocemod.2009.03.003
  12. D'Ovidio, F., Fernandez, V., Hernandez-Garcia, E. and Lopez, C. (2004). Mixing structures in the Mediterranean Sea from finitesize Lyapunov exponents. Geophys. Res. Lett., Vol.31(L17203). https://doi.org/10.1029/2004GL020328
  13. D'Ovidio, F., Fernandez, V., Lopez, C., Hernandez-Garcia, E. and Garcia-Ladon, E. (2009). Comparison between Eulerian diagnostics and finite-size Lyapunov exponents computed from altimetry in the Algerian basin. Deep-Sea Res. I., Vol. 56, 15-31. https://doi.org/10.1016/j.dsr.2008.07.014
  14. Haller, G. (2001). Distinguished material surface and coherent structures in three-dimensional fluid flows. Physica D, Vol. 149, 248-277. https://doi.org/10.1016/S0167-2789(00)00199-8
  15. Haller, G. (2002). Lagrangian coherent structures from approximate velocity data. Phys. Fluids, 14(6), 1851-1861. https://doi.org/10.1063/1.1477449
  16. Haller, G. and Yuan, G. (2000). Lagrangian coherent structures and mixing in two-dimensional turbulence. Physica D, Vol. 147, 352-370. https://doi.org/10.1016/S0167-2789(00)00142-1
  17. Halliwell, G. (2004). Evaluation of vertical coordinate and vertical mixing algorithms in the HYbrid-Coordinate Ocean Model (HYCOM). Ocean Modelling, Vol. 7, 285-322. https://doi.org/10.1016/j.ocemod.2003.10.002
  18. Harrison, C.S. and Glatzmaier, G.A. (2012). Lagrangian coherent structures in the California Current System - sensitivities and limitations. Geophys. Astrophys. Fluid Dynam. 106(1), 22-44. https://doi.org/10.1080/03091929.2010.532793
  19. Haza, A.C., Poje, A.C., Ozgokmen, T.M. and Martin, P. (2008). Relative dispersion from a high-resolution coastal model of the Adriatic Sea. Ocean Modelling, Vol. 22, 48-65. https://doi.org/10.1016/j.ocemod.2008.01.006
  20. Haza, A.C., Ozgokmen, T.M., Griffa, A., Molcard, A., Poulain, P.M. and Peggion, G. (2010). Transport properties in small-scale coastal flows: relative dispersion from VHF radar measurements in the Gulf of La Spezia. Ocean Dynamics, Vol. 60, 861-882. https://doi.org/10.1007/s10236-010-0301-7
  21. Haza, A.C., Ozgokmen, T.M., Griffa, A., Garraffo, J.D. and Piterbarg, L. (2012). Parameterization of particle transport at sumesoscales in the Gulf Stream region using Lagrangian subgrid models. Ocean Modelling, Vol. 42, 31-49. https://doi.org/10.1016/j.ocemod.2011.11.005
  22. Isern-Fontanet, J., Font, J., Garcia-Ladona, E., Emelianov, M., Millot, C. and Taupier-Letage, I. (2004). Spatial structure of anticyclonic eddies in the Algerian basin (Mediterranean Sea) analyzed using the Okubo-Weiss parameter. Deep-Sea Res. II. Vol. 51, 3009-3028. https://doi.org/10.1016/j.dsr2.2004.09.013
  23. Isern-Fontanet, J., Garcia-Ladona, E. and Font, J. (2006). Vortices of the Mediterranean Sea: an altimetric perspective. J. Phys. Oceanogr. Vol. 36, 87-103. https://doi.org/10.1175/JPO2826.1
  24. Joseph, B. and Legras, B. (2002). Relation between kinematic boundaries, stirring, and barriers for the Antarctic polar vortex. J. Atmosph. Sci. Vol. 59, 1198-1212. https://doi.org/10.1175/1520-0469(2002)059<1198:RBKBSA>2.0.CO;2
  25. Kantha, L.H. and Clayson, C.A. (2000). Small scale processes in geophysical fluid flows. 1st Ed. Academic Press.
  26. Klein, P. and Lapeyre, G. (2009). The oceanic vertical pump induced by mesoscale and submesoscale turbulence. Ann. Rev. Marine Sci. Vol. 1, 351-375. https://doi.org/10.1146/annurev.marine.010908.163704
  27. Lacorata, G., Aurell, E. and Vulpani, A. (2001). Drifter dispersion in the Adriatic Sea: Lagrangian data and chaotic model. Ann. Geophys. Vol. 19, 121-129. https://doi.org/10.5194/angeo-19-121-2001
  28. Legal, C., Klein P., Treguier, A. and Paillet, J. (2007). Diagnosis of the vertical motions in a mesoscale stirring region. J. Phys. Oceanogr. 37(5), 1413-1424. https://doi.org/10.1175/JPO3053.1
  29. Lepeyre, G. and Klein, P. (2006). Impact of the small-scale elongated filaments on the oceanic vertical pump. J. Marine Res. Vol. 64, 835-851. https://doi.org/10.1357/002224006779698369
  30. Lepeyre, G., Klein, P. and Hua, B.L. (2006). Ocean restratification forced by surface frontogenesis. J. Phys. Oceanogr. Vol. 36, 1577-1590. https://doi.org/10.1175/JPO2923.1
  31. Lekien, F., Shadden, S. and Marsden, J.E. (2007). Lagrangian coherent structures in n-dimensional systems. J. Math. Phys. Vol. 48(065404). https://doi.org/10.1063/1.2740025
  32. Levy, M., Klein P. and Treguier, A. (2001). Impact of sub-mesoscale physics on production and subduction of phytoplankton in an oligotrophic regime. J. Marine Res. 59(4), 535-565. https://doi.org/10.1357/002224001762842181
  33. Lumpkin, R. and Elipot, S. (2010). Surface drifter pair in the North Atlantic. J. Geophys. Res. Vol. 115 1-20.
  34. Mahadevan, A. and Tandon, A. (2006). An analysis of mechanisms for submesoscale vertical motion at ocean fronts. Ocean Modelling, Vol. 14, 241-256. https://doi.org/10.1016/j.ocemod.2006.05.006
  35. Martin, A.P. and Richards, K.J. (2001). Mechanisms for vertical nutrient transport within a North Atlantic mesoscale eddy. Deep Sea Res. II, 48(4-5), 757-773. https://doi.org/10.1016/S0967-0645(00)00096-5
  36. McGillicuddy Jr. D.J., Anderson, L.A., Bates, N.R., Bibby, T., Buesseler, K.O., Carlson, C.A., Davis, C.S., Ewart, C., Falkowski, P.G., Goldthwait, S.A., Hansell, D.A., Jenkins, W.J., Johnson, R., Kosnyrev, V.K., Ledwell, J.R., Li, Q.P., Siegel, D.A. and Steinberg, D.K. (2007). Eddy/wind interactions stimulate extraordinary mid-ocean plankton blooms. Science, Vol. 316, 1021-1025. https://doi.org/10.1126/science.1136256
  37. McWilliams, J.C., (2008). Fluid dynamics at the margin of rotational control. Environ. Fluid Mech., Vol. 8, 441-449. https://doi.org/10.1007/s10652-008-9081-8
  38. Mensa, J., Griffa, A., Garraffo, Z., Ozgokmen, T.M., Haza, A.C., and Veneziani, M. (2013). Seasonality of the submesoscale dynamics in the Gulf Stream region. Ocean Dynamics, Vol. 63, 923-941. https://doi.org/10.1007/s10236-013-0633-1
  39. Mezic, I. and Wiggins, S. (1994). On the integrability and perturbation of three-dimensional fluid-flows with symmetry. J. Nonlinear Sci. Vol. 4, 157-194. https://doi.org/10.1007/BF02430631
  40. Muller, P., McWilliams, J. and Molemaker, J. (2005). Routes to dissipation in the ocean: the two-dimensional/three-dimensional turbulence conundrum. In: Baumert, H.Z., Simpson, J., Sundermann, J.(Eds.), Marine turbulence: Theories, Observation, and Models. Results of the CARTUM project. Cambridge University Press, 397-405.
  41. Olascoaga, M.J., Rypina, I.I., Brown, M.G., Beron-Vera, F.J., Kocak, H., Brand, L.E., Halliwell, G.R. and Shay, L.K. (2006). Persistent transport barrier on the west Florida shelf. Geophys. Res. Lett., Vol. 33(L22603). https://doi.org/10.1029/2006GL027800
  42. Ozgokmen, T.M, Poje, A.C., Fisher, P.F., and Haza, A.C. (2011). Large eddy simulation of mixed layer instabilities and sampling strategies. Ocean Modelling, Vol. 39, 311-331. https://doi.org/10.1016/j.ocemod.2011.05.006
  43. Ozgokmen, T.M, Poje, A.C., Fisher, P.F., Childs, H., Krishnan, H., Garth, C., Haza, A.C., and Ryan, E. (2012). On multi-scale dispersion under the influence of surface mixed layer instabilities and deep flows. Ocean Modelling, Vol. 54, 16-30.
  44. Pasquero, C., Provenzale, A. and Weiss, J. (2002). Vortex statistics from Eulerian and Lagrangian time series. Physics Rev. Lett. Vol. 89(28).
  45. Poje, A.C., Haza, A.C., Ozgokmen, T.M., Magaldi, M.G., and Garraffo, G.D. (2010). Resolution dependent relative dispersion statistics in a hierarchy of ocean models. Ocean Modelling, Vol. 31, 36-50. https://doi.org/10.1016/j.ocemod.2009.09.002
  46. Quentel, E., Carton, X., Gutscher, M.-A., and Hobbs, R. (2010). Detecting and characterizing mesoscale and submesoscale structures of Mediterranean water from joint seismic and hydrographic measurements in the Gulf of Cadiz. Geophys. Res. Lett. Vol. 37(L06604).
  47. Richards, K.J., Kashino, Y., Natarov, A. and Firing, E. (2012). Mixing in the western equatorial Pacific and its modulation by ENSO. Geophys. Res. Lett. Vol. 39(L02604).
  48. Schroeder, K., Chigiato, J., Haza, A., Griffa, A., Ozgokmen, T.M., Zanasca, P., Molcard, A., Borghini, M., Poulain, P.M., Gerin, R., Zambianchi, E., Falco, P., and Trees, C. (2012). Targeted Lagrangian sampling of submesoscale dispersion at a coastal frontal zone. Geophys. Res. Lett. Vol. 39, 4-9.
  49. Shadden, S.C., Lekien, F., and Marsden, J.E. (2005). Definition and properties of Lagrangian coherent structures from finite-time Lyapunov exponents in two-dimensional aperiodic flows. Physica D. Vol. 212, 271-304. https://doi.org/10.1016/j.physd.2005.10.007
  50. Sweeney, E.N., McGillicuddy, D.J. and Buesseler, K.O. (2003). Biogeochemical impacts due to mesoscale eddy activity in the Sargasso Sea as measured at the Bermuda Atlantic Time-series Study (BATS). Deep Sea Res. II, Vol. 50, 3017-3039. https://doi.org/10.1016/j.dsr2.2003.07.008
  51. Waugh, D.W., Keating, S.R., and Chen, M.L. (2012). Diagnosing ocean stirring: Comparison of relative dispersion and finite-time Lyapunov exponents. Physica D. Vol. 212, 271-304.
  52. Wilson, W.D., Johns, W.E. and Garzoli, S.L. (2002). Velocity structure of North Brazil Current rings. Geophys. Res. Lett. Vol. 29(8).