Instability of the North Pacific subtropical countercurrent

Y. L. Chang, L. Y. Oey*

*此作品的通信作者

    研究成果: 雜誌貢獻期刊論文同行評審

    26 引文 斯高帕斯(Scopus)

    摘要

    The North Pacific Subtropical Countercurrent (STCC) has a weak eastward velocity near the surface, but the region is populated with eddies. Studies have shown that the STCC is baroclinically unstable with a peak growth rate of 0.015 day-1 in March, and the ~60-day growth time has been used to explain the peak eddy kinetic energy (EKE) in May observed from satellites. It is argued here that this growth time from previously published normal-mode instability analyses is too slow. Growth rates calculated from an initial-value problem without the normal-mode assumption are found to be 1.5 to 2 times faster and at shorter wavelengths, due to the existence of (i) nonmodal solutions and (ii) sea surface temperature front in the mixed layer in winter. At interannual time scales it is shown that because of rapid surface adjustments, the STCC geostrophic shear, hence also the instability growth, is approximately in phase with surface forcing, leading to EKE modulation that peaks approximately 10 months later. However, the EKE can only be partially explained by this mechanism of modulation by baroclinic instability. It is suggested that the unexplained variance may be caused additionally by modulation of the EKE by dissipation.

    原文英語
    頁(從 - 到)818-833
    頁數16
    期刊Journal of Physical Oceanography
    44
    發行號3
    DOIs
    出版狀態已發佈 - 2014 三月 1

    ASJC Scopus subject areas

    • 海洋學

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