Strong Intraseasonal Variability of Meridional Currents near 5°N in the Eastern Indian Ocean: Characteristics and Causes

DOI PDF XML XML 被引用文献3件
  • Gengxin Chen
    State Key Laboratory of Tropical Oceanography, South China Sea Institute of Oceanology, Chinese Academy of Sciences, Guangzhou, China, and Department of Atmospheric and Oceanic Sciences, University of Colorado Boulder, Boulder, Colorado
  • Weiqing Han
    Department of Atmospheric and Oceanic Sciences, University of Colorado Boulder, Boulder, Colorado
  • Yuanlong Li
    Department of Atmospheric and Oceanic Sciences, University of Colorado Boulder, Boulder, Colorado
  • Michael J. McPhaden
    National Oceanic and Atmospheric Administration/Pacific Marine Environmental Laboratory, Seattle, Washington
  • Ju Chen
    State Key Laboratory of Tropical Oceanography, South China Sea Institute of Oceanology, Chinese Academy of Sciences, Guangzhou, China
  • Weiqiang Wang
    State Key Laboratory of Tropical Oceanography, South China Sea Institute of Oceanology, Chinese Academy of Sciences, Guangzhou, China
  • Dongxiao Wang
    State Key Laboratory of Tropical Oceanography, South China Sea Institute of Oceanology, Chinese Academy of Sciences, Guangzhou, China

書誌事項

公開日
2017-05
DOI
  • 10.1175/jpo-d-16-0250.1
公開者
American Meteorological Society

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<jats:title>Abstract</jats:title><jats:p>This paper reports on strong, intraseasonal, upper-ocean meridional currents observed in the Indian Ocean between the Bay of Bengal (BOB) and the equator and elucidates the underlying physical processes responsible for them. In situ measurements from a subsurface mooring at 5°N, 90.5°E reveal strong intraseasonal variability of the meridional current with an amplitude of ~0.4 m s<jats:sup>−1</jats:sup> and a typical period of 30–50 days in the upper 150 m, which by far exceeds the magnitudes of the mean flow and seasonal cycle. Such prominent intraseasonal variability is, however, not seen in zonal current at the same location. Further analysis suggests that the observed intraseasonal flows are closely associated with westward-propagating eddylike sea surface height anomalies (SSHAs) along 5°N. The eddylike SSHAs are largely manifestations of symmetric Rossby waves, which result primarily from intraseasonal wind stress forcing in the equatorial waveguide and reflection of the equatorial Kelvin waves at the eastern boundary. Since the wave signals are generally symmetric about the equator, similar variability is also seen at 5°S but with weaker intensity because of the inclined coastline at the eastern boundary. The Rossby waves propagate westward, causing pronounced intraseasonal SSHA and meridional current in the upper ocean across the entire southern BOB between 84° and 94°E. They greatly weaken in the western Indian Basin, but zonal currents near the equator remain relatively strong.</jats:p>

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