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首页> 外文期刊>Journal of Physical Oceanography >Seasonal Modulations in the Eddy Field of the South Pacific Ocean
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Seasonal Modulations in the Eddy Field of the South Pacific Ocean

机译：南太平洋涡流场中的季节性变化

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Decade-long satellite altimeter data from the Ocean Topography Experiment (TOPEX)/Poseidon and European Remote Sensing Satellite-1 and -2 (ERS-1/2) missions are analyzed to investigate the eddy signals in the South Pacific Ocean. High-eddy kinetic energy (EKE) bands with well-defined annual cycles are detected along the eastward-flowing surface currents of the South Tropical Countercurrent (STCC) between 21°-29°S and the South Equatorial Countercurrent (SECC) centered near 9°S. Overriding the westward-flowing South Equatorial Current (SEC), the STCC layer has the sign of its mean potential vorticity gradient opposite to that in the SEC layer, subjecting the vertically sheared STCC-SEC system to baroclinic instability. In austral winter, the STCC-SEC system is baroclinically more unstable than in other seasons because of the large vertical shear and weak stratification. This seasonal variation in the intensity of baroclinic instability is responsible for the seasonal modulation of the STCC's EKE field with a November-December maximum and a June-July minimum. The large deformation radius in the low-latitude SECC region, on the other hand, prevents the vertically sheared SECC-SEC system from becoming baroclinically unstable. With the broad, westward-flowing SEC weakening the stabilizing planetary β effect, the high EKE level observed along the SECC is found to result from the barotropic instability associated with the horizontal shear of the SECC-SEC system. Together with an analysis of energetics, it is shown that the seasonal variation in the intensity of barotropic instability accounts for the seasonal modulation of the SECC's EKE field, with a maximum in April and a minimum in August.
机译：分析了来自海洋地形实验（TOPEX）/波塞冬和欧洲遥感卫星1号和-2号（ERS-1 / 2）任务的十年卫星高度计数据，以调查南太平洋的涡流信号。在21°-29°S之间的南热带逆流（STCC）和以9为中心的南赤道逆流（SECC）的东流表面流中，检测到具有明确年循环的高涡动能（EKE）带°S。 STCC层覆盖了向西流动的南赤道流（SEC），其平均潜在涡度梯度与SEC层相反，使垂直剪切的STCC-SEC系统遭受斜压不稳定。在南方冬季，由于大的垂直剪切力和较弱的分层，STCC-SEC系统比其他季节的斜压不稳定。斜压不稳定强度的这种季节性变化是STCC EKE场的季节调制的原因，最大值为11月至12月，最小为6月至7月。另一方面，低纬度SECC区域中较大的变形半径可防止垂直剪切的SECC-SEC系统变得斜压不稳定。随着宽大的，向西流动的SEC减弱了稳定的行星β效应，发现沿着SECC观测到的高EKE水平是由于与SECC-SEC系统的水平剪切有关的正压不稳定引起的。连同能量学分析，结果表明，正压不稳定强度的季节变化是SECC EKE场的季节调制，最大的出现在4月，最小的出现在8月。

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