Near-Surface Shear Flow in the Tropical Pacific Cold Tongue Front*
Near-Surface Shear Flow in the Tropical Pacific Cold Tongue Front*
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DOI：
10.1175/2008jpo4064.1
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发表时间：
2009-05
影响因子：
3.5
通讯作者：
M. Cronin;W. Kessler
中科院分区：
文献类型：
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作者：
M. Cronin;W. Kessler
利用2004 - 2005年9个月的5 ~ 25 m系泊流仪，对太平洋冷舌锋在2°N， 140°W的近地表切变进行了观测。平均近地面流强烈向西，仅微弱向北（~ 3 cm s−1）。平均近地面切变主要向西，因此，朝向东南贸易的左侧。当从观测到的切变中减去西南地转切变后，相对于25 m的剩余地转流向北，具有类似Ekman的螺旋，与针对垂直均匀锋区域修正的Ekman模式在质量上一致。根据“锋面埃克曼”模式，地转涡旋螺旋是由地面地转切变不平衡的那部分风应力所强迫的。对复合热带不稳定波（TIW）的分析证实，当风沿锋面吹时，地转切变最小，而当风斜向锋面吹时，地转切变增强。Furthe……
Abstract Near-surface shear in the Pacific cold tongue front at 2°N, 140°W was measured using a set of five moored current meters between 5 and 25 m for nine months during 2004–05. Mean near-surface currents were strongly westward and only weakly northward (∼3 cm s−1). Mean near-surface shear was primarily westward and, thus, oriented to the left of the southeasterly trades. When the southwestward geostrophic shear was subtracted from the observed shear, the residual ageostrophic currents relative to 25 m were northward and had an Ekman-like spiral, in qualitative agreement with an Ekman model modified for regions with a vertically uniform front. According to this “frontal Ekman” model, the ageostrophic Ekman spiral is forced by the portion of the wind stress that is not balanced by the surface geostrophic shear. Analysis of a composite tropical instability wave (TIW) confirms that ageostrophic shear is minimized when winds blow along the front, and strengthens when winds blow oblique to the front. Furthe...