Barotropic feature of ocean striations in the North Pacific
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摘要: 海洋中包含着多种时空尺度的运动过程，海洋带状流是近年来发现的一种新的流动形式。这种流动现象介于地转湍流和准定常流之间。上层海洋中大尺度运动的强度远大于海洋带状流而将其遮盖，因而带状流需要借助滤波方法提取出来。本研究基于纬向速度数据，通过切比雪夫高通滤波提取了北太平洋海洋带状流的三维结构，定义了“流向稳定度”指数，量化分析了北太平洋海域带状流的正压特性，从而进一步加深了对北太平洋海洋带状流结构特征的认识。Abstract: The ocean contains various spatiotemporal scales of motion processes, and ocean striations are a newly discovered form of flow in recent years. This flow phenomenon lies between geostrophic turbulence and quasi-steady flow. Due to the dominance of large-scale motion in the upper ocean, ocean striations are masked and need to be extracted using filtering methods. In this study, the three-dimensional structure of ocean striations in the North Pacific was extracted based on zonal velocity data using Chebyshev high-pass filtering. The “flow stability” index was defined to quantitatively analyze the barotropic feature of ocean striations in the North Pacific, thereby deepening the understanding of the structural characteristics of ocean striations in the North Pacific.
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Key words:
- striations /
- the North Pacific /
- barotropy
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图 2 基于SODA数据的北太平洋997 m深度上带状流流速（a）、流向（b）、在不同深度上流向不变和发生变化的区域（c）和流向稳定度（d）
偏黄色区域表示流向在深度上稳定度较高的区域，偏蓝色区域则表示流向在深度上稳定度较低的区域
Fig. 2 Based on SODA data, the striations current velocity at 997 m in the North Pacific (a), flow direction (b), regions of flow direction vertically in alignment and regions where flow direction changes at different depths (c), and the stability of flow direction (d)
The yellow region indicates the area where the flow direction is stable over the depth, while the blue region indicates the area where the flow direction varies over the depth
图 3 基于SODA数据，带状流宽度在3个经度范围内随纬度的变化
橙色，红色，紫色和银色4条细线代表4种深度上的带宽变化情况，黑色粗实线表示以上4种深度上的平均，其中3个经度范围在图4中用黑框表明
Fig. 3 Based on SODA data, the meridional variability of bandwidth of the striations over three longitudinal bands
The four thin lines (orange, red, purple and silver) depict the meridional distribution of bandwidth at four depths, while the heavy black lines represent the average over these four depths. The three longitude ranges are indicated by black boxes in Fig. 4
图 4 基于SODA数据的北太平洋997 m深度上的带状流流速和流向稳定度
偏黄色区域表示流向在深度上稳定的区域，偏蓝色区域则表示流向在深度上稳定度较差的区域
Fig. 4 Based on SODA data, the striations at current velocity at 997 m and the stability of flow direction in the North Pacific
The yellow region indicates the area where the flow direction is stable over the depth, while the blue region indicates the area where the flow direction varies over the depth
图 5 基于ECCO2数据的北太平洋1007 m深度上的带状流流速和流向稳定度
偏黄色区域表示流向在深度上稳定的区域，偏蓝色区域则表示流向在深度上稳定度较差的区域
Fig. 5 Based on ECCO2 data, the striations at current velocity at 1 007 m and the stability of flow direction in the North Pacific
The yellow region indicates the area where the flow direction is stable over the depth, while the blue region indicates the area where the flow direction varies over the depth
图 6 SODA数据中的180°剖面的不同深度纬向流流速（a）、不同深度滤波后分离出的带状流流速（b）以及纬向流和带状流流场的斜压分量指数随纬度的变化（c）
蓝色和红色的实线分别为纬向流和带状流斜压分量指数的变化，蓝色和红色的虚线则分别为两者的均值；灰色阴影部分为斜压分量指数小于0.5的区域
Fig. 6 Based on SODA data, zonal flow current velocity along 180° in different depths (a), striations current velocity obtained after filtering in different depths (b), and BCF index for the zonal flow and striation (c)
Where the blue (red) solid line for the zonal flow (striation) BCF index, and the blue (red) dashed line for the mean values; the shaded area indicates BCF index less than 0.5
图 7 ECCO2数据中180°剖面的不同深度纬向流流速（a）、不同深度滤波后分离出的带状流流速（b）以及纬向流和带状流流场的斜压分量指数随纬度的变化（c）
蓝色和红色的实线分别为纬向流和带状流斜压分量指数的变化，蓝色和红色的虚线则分别为两者的均值；灰色阴影部分为斜压分量指数小于0.5的区域
Fig. 7 Based on ECCO2 data, zonal flow current velocity along 180° in different depths (a), striations current velocity obtained after filtering in different depths (b), and BCF index for the zonal flow and striation (c)
Where the blue (red) solid line for the zonal flow (striation) BCF index, and the blue (red) dashed line for the mean values; the shaded area indicates BCF index less than 0.5
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