Nonlinear vorticity balance of the Subantarctic Front in the southeast Pacific
Nonlinear vorticity balance of the Subantarctic Front in the southeast Pacific
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东南太平洋亚南极锋的非线性涡度平衡
DOI：
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发表时间：
2010
期刊：
影响因子：
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通讯作者：
B. Sloyan
中科院分区：
文献类型：
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作者：
T. Chereskin;L. Talley;B. Sloyan
[1] 通过 2005 年和 2006 年的调查，使用船上直接速度观测和降低的声学多普勒电流剖面仪来检查东太平洋隆起和德雷克海峡之间的亚南极锋 (SAF) 的速度和涡度结构。SAF 的特点是在该地形相对平滑的区域中水平波长约 250-300 公里的曲折。观察到深度平均 SAF 射流与 150 m 处的流紧密一致，就像等效的正压流一样。正压或深度平均涡度表现出行星涡度的平流与相对涡度之间的平衡，正如在平均流中的多普勒频移短正压罗斯贝波中所看到的那样。隐含的波速与观测到的当前速度范围一致。与涡度平衡一致的水流垂直结构的指数拟合表明垂直衰减尺度约为 1900 m。 150 m 处的涡度平衡意味着表面发散，必须在深度处通过相反符号的发散来平衡。计算证实了 Hughes（2005）对该地区的初步结论，该结论基于地表气候学，但表明了更大的垂直衰减规模和波速。
[1] Direct velocity observations from shipboard and lowered acoustic Doppler current profilers are used to examine the velocity and vorticity structure of the Subantarctic Front (SAF) between the East Pacific Rise and Drake Passage from surveys made in 2005 and 2006. The SAF is characterized by meanders of horizontal wavelength approximately 250–300 km in this region of relatively smooth topography. The depth-averaged SAF jet is observed to be closely aligned with the flow at 150 m, as in an equivalent barotropic flow. The barotropic or depth-averaged vorticity exhibits a balance between advection of planetary vorticity and relative vorticity, as would be seen in a Doppler-shifted short barotropic Rossby wave in a mean flow. The implied wave speed is consistent with the observed range of current speeds. An exponential fit to the vertical structure of the current consistent with the vorticity balance suggests a vertical decay scale of about 1900 m. The vorticity balance at 150 m implies a surface divergence which must be balanced at depth by a divergence of the opposite sign. The calculation confirms the tentative conclusions of Hughes (2005) for this region, which were based on a surface climatology but indicates a larger vertical decay scale and wave speed.