Advertisement

Scale dependence of divergence and vorticity of near-surface flows in the sea

Part 1. Measurements and calculations of area-averaged divergence and vorticity
  • Hideo Kawai
Article

Abstract

To area-average the horizontal divergence and the vertical component of vorticity, three methods are proposed and examined. The polygon method is based on deformations of a polygon made by connecting drifters. They are deployed at widely different scales of 1 cm 1,000 km and tracked using various procedures. The loop method is adopted when a drifter completes at least two loops of trajectory in a tidal vortex, a ring or a gyre. Even if data for a drifter completing only one loop is available, the vorticity can be calculated. The crossing method is applied to the GEK data on the circumference of a Kuroshio ring. The data which will be used to calculate them in Part 2 are summarized in tables. Offset dispositions of positive and negative divergences or vorticities on a horizontal plane and in a water column are shown. Probably, the vertical offset of vorticities does not occur in general. The area-turnover of a polygon of drifters are discussed. Sampling time-intervals, appropriate to the scale of the area, for the polygon and loop methods are examined. A first impression of Rhines' (1979) sketch has produced a misunderstanding that the polygon method would be useless because a limited number of drifters cannot follow such a complicated deformation of the material line over a long period. It is shown that adopting a short time-scale appropriate to the length scale furnishes a practical solution to the problem.

Keywords

Vortex Water Column Vorticity Horizontal Plane Vertical Component 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

Preview

Unable to display preview. Download preview PDF.

Unable to display preview. Download preview PDF.

References

  1. Aota, M. (1984): Oceanographic structure of the Soya Warm Current. Bull. on Coastal Oceanogr.,22, 30–39 (in Japanese).Google Scholar
  2. Cheney, R. E., P. L. Richardson and K. Nagasaka (1980): Tracking a Kuroshio cold ring with a free-drifting surface buoy. Deep-Sea Res.,27, 641–654.CrossRefGoogle Scholar
  3. Chew, F. and G. A. Berberian (1971): A determination of horizontal divergence in the Gulf Stream off Cape Lookout. J. Phys. Oceanogr.,1, 39–44.CrossRefGoogle Scholar
  4. Garrett, J. (1981): Oceanographic features revealed by the FGGE drifting buoy array, p. 61–69. In: Oceanography from Space, ed. by J.F.R. Gower, Plenum Publ. Corp.Google Scholar
  5. Ishii, H, R. Saruwatari, Y. Ueno, S. Kuramoto and H. Nishida (1982): Application of drifting buoys in ocean research. Rep. Hydrogr. Res.,17, 347–365.Google Scholar
  6. Kashiwai, M. and M. Ueno (1981): Observation results of distributions of temperature, salinity, D.O., inflow and outflow in Kumihama Bay. Survey Rep. of Shallow Water Fish. Exploit. in 1979–80 (Kumihama Area) by Kyoto Pref., 10–20 (in Japanese).Google Scholar
  7. Kawai, H., H. Sakamoto and M. Momota (1969): A study on convergence and divergence in surface layer of the Kuroshio-I: Direct measurement and interpretation of convergence and divergence at the surface. Bull. Nansei Reg. Fish. Res. Lab., 1, 1–14 (in Japanese).Google Scholar
  8. Kawai, H. and H. Sakamoto (1970): A study on convergence and divergence in surface layer of the Kuroshio-II: Direct measurement of convergence and divergence at the top and bottom of surface mixed layer. Bull. Nansei Reg. Fish. Res. Lab.,2, 19–38 (in Japanese).Google Scholar
  9. Kawai, H. (1976): Convergence, divergence and the physical oceanography of particles. p. 103–155. In: Physical Oceanography II, ed. by T. Teramoto, Tokyo Univ. Press. (in Japanese).Google Scholar
  10. Kawai, H. (1979): A detailed survey of current structure and its probable effect on accumulation and dispersal of floating particles. Fish. Engin.,16, 25–32 (in Japanese).Google Scholar
  11. Kawai, H. (1985): Scale dependence of divergence and vorticity of near-surface flows in the sea. Part 2. Results and interpretation. J. Oceanogr. Soc. Japan,41, 167–175.Google Scholar
  12. Kirwan, A.D. (1975): Oceanic velocity gradients. J. Phys. Oceanogr.,5, 729–735.CrossRefGoogle Scholar
  13. Kirwan, A.D., G.J. McNally, E. Reyna and W.J. Merrell (1978): The near-surface circulation of the eastern North Pacific. J. Phys. Oceanogr.,8, 937–945.CrossRefGoogle Scholar
  14. Komatsu, T. (1984): Current structure around a Sargassum forest. Preprint for the 1984 fall meeting of Oceanogr. Soc. Japan, 32–33 (in Japanese).Google Scholar
  15. Kyoto Pref. Fish. Exp. Stn. (1966): Prompt Rep. of A Joint Oceanogr. Observations in Wakasa Bay in 1965. 6 pp. (in Japanese).Google Scholar
  16. McCartney, M.S., L.V. Worthington and W.J. Schmitz, Jr. (1978): Large cyclonic rings from the northeast Sargasso Sea. J. Geophys. Res.,83, 901–914.Google Scholar
  17. McNally, G. J. (1981): Satellite-tracked drift buoy observations of the near-surface flow in the eastern mid-latitude North Pacific. J. Geophys. Res.,86(C9), 8022–8030.Google Scholar
  18. Molinari, R. and A.D. Kirwan (1975): Calculations of differential kinematic properties from Lagrangian observations in the western Caribbean Sea. J. Phys. Oceanogr.,5, 483–491.CrossRefGoogle Scholar
  19. Nishida, H. (1978): Observations with satellite-tracked drifters, p. 81–90. In: The Kuroshio Meander and Cold Water Mass, 1. (in Japanese).Google Scholar
  20. Ogawa, Y., T. Miita, A. Ichihara, Y. Hasegawa and N. Inoue (1978): Fluctuations of the Tsushima Current measured with the current drogue. Bull. Seikai Reg. Fish. Res. Lab.,51, 13–44.Google Scholar
  21. Reed, R.K. (1971): An observation of divergence in the Alaskan Stream. J. Phys. Oceanogr.,1, 282–283.CrossRefGoogle Scholar
  22. Reed, R.K. (1980): Direct measurement of recirculation in the Alaskan Stream. J. Phys. Oceanogr.,10, 976–978.CrossRefGoogle Scholar
  23. Rhines, P.B. (1979): Geostrophic turbulence. Ann. Rev. Fluid Mech.,11, 401–441.CrossRefGoogle Scholar
  24. Richardson, P.L. (1980): Gulf Stream ring trajectories. J. Phys. Oceanogr.,10, 90–104.CrossRefGoogle Scholar
  25. Stommel, H. (1949): Horizontal diffusion due to oceanic turbulence. J. Mar. Res.,8, 199–225.Google Scholar
  26. Toda, S. (1983): On wave-induced circulation. Model experiment and current observation off Taro Coast. Fish. Engin.,20(1), 65–74 (in Japanese).Google Scholar
  27. Tomosada, A. (1975): Observations of a warm eddy detached from the Kuroshio east of Japan. Bull. Tokai Reg. Fish. Res. Lab.,81, 13–85 (in Japanese).Google Scholar

Copyright information

© Oceanographical Society of Japan 1985

Authors and Affiliations

  • Hideo Kawai
    • 1
  1. 1.Department of FisheriesKyoto UniversityKyotoJapan

Personalised recommendations