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Bimonthly Variability in Zonal Velocity at Middepths of the Equatorial Indian Ocean



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  • Journal Title:
    Journal of Physical Oceanography
  • Personal Author:
  • NOAA Program & Office:
  • Description:
    Intraseasonal variability in zonal velocity at middepths (between 450 and 800 m) of the equatorial Indian Ocean is investigated using in situ velocity measurements for the period from 2014 to 2019 at 0°, 83°E and the output of a wind-forced ocean general circulation model (OGCM). The spectral analysis of observed zonal velocity indicates that the highest energy peak at middepths on intraseasonal time scales is at the period of about 57 days between 450- and 800-m depths. The OGCM is able to simulate the spectral peak qualitatively. The statistical analysis using model output shows that the meridional structure, zonal wavelength, and vertical wavelength of 57-day variability in zonal velocity are consistent with those of a free, first meridional mode Rossby wave in an ocean at a state of rest. Two possibilities are discussed as the energy source of middepth 57-day variability. The first is that variability near the surface propagates to middepths as a wind-forced linear Rossby wave. This possibility is partly supported by the analysis of wave rays, which connect the spectral peak of surface zonal velocity with the analysis region at the middepths. The second possibility is the supply of energy by nonlinear advection, which is supported by the results obtained from the zonal kinetic energy budget. It is found that the forcing by advection propagates to the west at a similar phase speed to that of zonal velocity, suggesting a resonant forcing.
  • Source:
    Journal of Physical Oceanography, 55(7), 865-881
  • Series:
    PMEL contribution   no. 5698
  • DOI:
  • ISSN:
    0022-3670 ; 1520-0485
  • Format:
    pdf
  • Publisher:
    American Meteorological Society
  • Document Type:
    Journal Article
  • Rights Information:
    Other
  • Compliance:
    Submitted
  • Main Document Checksum:
    urn:sha-512:8afc0b91416139955504e3e95c2c8e908a73c2e02821e56ac9f4ef0b6f2adf4bfecdfaf93563029123abc168720e8f5919d78bf0dc736aae8c28342a47873daa
  • Download URL:
  • File Type:
    Filetype[PDF - 7.69 MB ]
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