沿岸风和海洋波动在北向索马里流生成中的作用
储小青(1984—), 女, 广东省广州市人, 副研究员, 博士, 研究方向为物理海洋学。email: |
Copy editor: 殷波
收稿日期: 2022-03-23
修回日期: 2022-05-19
网络出版日期: 2022-06-07
基金资助
国家自然科学基金项目(42076021)
国家自然科学基金项目(42005035)
广东省自然科学基金项目(2021A1515011534)
The role of alongshore wind and ocean wave in generating the northward Somali Current
Copy editor: YIN Bo
Received date: 2022-03-23
Revised date: 2022-05-19
Online published: 2022-06-07
Supported by
National Natural Science Foundation of China(42076021)
National Natural Science Foundation of China(42005035)
Guangdong Basic and Applied Basic Research Foundation(2021A1515011534)
基于同化资料和数值模式, 文章研究了北向索马里流(norward Somali current, NSC)的季节特征和产生机制。NSC在5月开始出现, 在8—9月向北延伸至近15°N, 并形成一个强盛的反气旋式环流。10月下旬, NSC开始减弱, 并于11月消失。NSC由局地沿岸风和东侧西传的海洋波动共同激发。在5—7月, 在局地西南沿岸风的协助下, 东非沿岸流(EACC)跨越赤道进入北印度洋, 形成了NSC。在8—10月, 即便无局地西南沿岸风, 在来自阿拉伯海东边界的海洋波动和EACC共同作用下, 依旧能形成NSC。研究表明, 局地沿岸风虽能诱发近岸的环流结构, 但NSC关联的影响范围较大的反气旋式环流结构则由西传的海洋波动所激发。
储小青 , 彭启华 . 沿岸风和海洋波动在北向索马里流生成中的作用[J]. 热带海洋学报, 2023 , 42(2) : 1 -8 . DOI: 10.11978/2022055
By analyzing reanalysis data and conducting ocean modes experiments, this study investigates the seasonal variation and dynamics of the norward Somali current (NSC) in the tropical Indian Ocean. The results show that the NSC starts from May, gradually strengthens and extends norward to 15°N during August-September, and forms a strong anti-cyclonic circulation — the Great Whirl. The NSC weakens significantly in late October, and disappears in November. The NSC results from local alongshore wind forcing and westward propagational Rossby waves. During May-July, alongshore wind forcing induces the East African Coast Current (EACC) to cross the equator to form the NSC. From August to October, even without alongshore wind forcing, the Rossby waves together with EACC can still form the NSC. Further analysis suggests that, although alongshore wind forcing incudes near-shore current, the Great Whirl is caused primarily by the Rossby waves. This research reveals dynamics of the NSC, and provides substantial evidences for ocean waves modulating ocean currents.
图1 模式试验中的风场设计方案(以西海盆气候态第一天风场为例)a. 控制试验(CR)中的原始风场; b. 敏感性试验(EXP)中的风场。其中红色箭头为CR和EXP的风场差异 Fig. 1 Comparison of wind stress used in CR and EXP. Taking the climatological wind stress on the first day in the western basin as an example, the black arrows in (a) and the blue arrows in (b) show the wind stress in CR and EXP, respectively. The red arrows in (b) present the difference of wind stress between CR and EXP |
图2 基于CCMP2得到的气候态风应力(箭头)及风应力旋度(wind stress curl, WSC, 填色)a. 1月; b. 4月; c. 7月; d. 10月 Fig. 2 Monthly climatological wind stress (vectors; unit: N·m-2) and WSC (color fill; unit: ×10-8N·m-3) from CCMP2 |
图3 基于ORAS4得到的气候态海表高度异常(sea surface height anomaly, SSHA, 填色)和上层100m平均流场流速(箭头)a. 4月; b. 5月; c. 6月; d. 7月; e. 8月; f. 9月; g. 10月; h. 11月。图中的红色圆圈为北向索马里流所在区域 Fig. 3 Evolution of monthly climatological sea surface height anomaly (color; unit: cm) and current averaged at the upper 100 m (vector; unit: m·s-1) during April—November from ORAS4 |
图4 基于ORAS4 (a~d)、HYCOM (e~h)和BRAN (i~l)的7°N经向速度图a, e, i: 5月; b, f, j: 7月; c, g, k: 9月; d, h, l: 11月。北向为正。图中等值线为经向流速(单位: m·s-1) Fig. 4 The meridional velocity at 7°N in May, July, September, and November from ORAS4 (the 1st row), HYCOM (the 2nd row), and BRAN (the 3rd row). Unit: m·s-1 |
图5 基于1.5层数模的控制实验CR的平均海表高度异常(SSHA, 填色)和上层100m平均流场流速(箭头)a. 4月; b. 5月; c. 6月; d. 7月; e. 8月; f. 9月; g. 10月; h. 11月; i. 12月; j. 1月; k. 2月; l. 3月 Fig. 5 Evolution of monthly climatological sea surface height anomaly (color; unit: cm) and current averaged at the upper 100 m (vector; unit: m·s-1) during April—November from the control experiment CR of 1.5-layer model with 12 months |
图7 基于1.5层数模的实验EXP得到的平均态海表高度异常(填色)和上层100m平均流场(箭头)a. 4月; b. 5月; c. 6月; d. 7月; e. 8月; f. 9月; g. 10月; h. 11月。图a中红框表示风场设置为0的区域 Fig. 7 Evolution of monthly climatological sea surface height anomaly (color; unit: cm) and current averaged at the upper 100 m (vector; unit: m·s-1) during April—November from the experiment EXP of 1.5-layer model. The red box in the first subplot shows the region where the wind stress is removed |
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