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首页> 外文期刊>Journal of Physical Oceanography >Latitudinal and Frequency Characteristics of the Westward Propagation of Large-Scale Oceanic Variability
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Latitudinal and Frequency Characteristics of the Westward Propagation of Large-Scale Oceanic Variability

机译：大规模海洋变化向西传播的纬度和频率特征

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摘要

In the open ocean away from the equator, westward propagation is a ubiquitous characteristic of oceanic variability. The objectives of the study are to investigate the latitudinal dependence of the frequency of westward-propagating variability. Two-dimensional Fourier analysis in frequency and zonal wavenumber is applied to time-longitude records of sea surface height data obtained from the Ocean Topography Experiment (TOPEX)/ Poseidon mission. The focus of the study is placed on spatial scales larger than the mesoscale. The frequency of westward propagation is generally lower than the critical frequency of the first-mode baroclinic Rossby waves, as expected from the conventional theory of Rossby waves in a midlatitude ocean. However, westward propagation with frequency of up to 2 times the critical frequency is also observed at most latitudes. This supercritical propagation can be explained by the effects of the vertical shear of the mean flow at midlatitudes and by the effects of the equatorial wave guide at the tropical latitudes. Westward propagation with frequency much higher than the critical frequency (by a factor of 5-10) is also observed at certain latitudes in all oceans. The most energetic cases are found along the latitudes of strong zonal jets, including the Brazil/Malvinas Confluence, the Agulhas Return Current, and the Gulf Stream Extension, with decreasing variance in the order. The high-frequency westward propagation exhibits the frequency and wavenumber characteristics of barotropic Rossby waves.
机译：在远离赤道的公海中，向西传播是海洋变化的普遍特征。该研究的目的是调查西向传播变异频率的纬度依赖性。频率和纬向波数的二维傅立叶分析应用于从海洋地形实验（TOPEX）/波塞冬任务获得的海面高度数据的时间经度记录。研究的重点放在比中尺度更大的空间尺度上。正如中纬度海洋中传统的罗斯比波理论所预期的那样，向西传播的频率通常低于一阶斜压罗斯比波的临界频率。但是，在大多数纬度上也观察到向西传播的频率高达临界频率的2倍。这种超临界传播可以由中纬度处的平均流量的垂直剪切作用和热带纬度处的赤道波导的作用来解释。在所有海洋的某些纬度处，也观察到向西传播的频率远高于临界频率（5-10倍）。最活跃的情况是在强纬向喷气带的纬度上发现的，包括巴西/马尔维纳斯汇合处，Agulhas回水流和墨西哥湾流扩展，其顺序逐渐减小。高频向西传播表现出正压罗斯比波的频率和波数特性。

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