The boundary currents east and north of Madagascar: 2. Direct measurements and model comparisons
The boundary currents east and north of Madagascar: 2. Direct measurements and model comparisons
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马达加斯加东部和北部边界流：2.直接测量和模型比较
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发表时间：
1988
期刊：
影响因子：
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通讯作者：
R. Zantopp
中科院分区：
文献类型：
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作者：
F. Schott;M. Fieux;J. Kindle;J. Swallow;R. Zantopp
在马达加斯加以东的边界流中进行了长达11个月的系泊流测量，在琥珀角S 12°附近，平均流向西北流动，在23°S附近，平均流大致向南流动。从150-1100米深度范围内的系泊水流测量得到的输运量与Swallow等人从船体截面得到的输运量吻合得很好。(本期)。在12°S，40~55天周期的边界流输送变化非常强烈，约占总输送方差的40%，而在23°S，40~55天的周期波动仅占总输送方差的15%。S 12°附近的波动似乎不是由局地风强迫引起的，在该周期带内没有出现能量峰值。尽管亚热带印度洋上的风强迫有很大的变化，但在系泊的海流和输送时间序列中无法检测到显著的年度循环。用两个不同的印度洋数值模式对观测结果进行了比较，这两个模式都是由Hellerman和Rosenstein(1983)的季节变化风强迫的。减重模式给出的平均边界流输送与观测值吻合较好，也显示了可以忽略的季节性周期。多层地球物理流体动力学实验室模型也显示出一个小的季节性周期。来自西副热带印度洋的观测证据似乎与巴哈马-安的列斯岛弧以东的副热带北大西洋的观测证据相似，在那里也没有发现显著的季节性边界流响应，尽管海洋上的风强迫有很大的年变化。对两个大洋的观测情况和数值模式结果进行了比较。
Moored current measurements of 11-month duration were carried out in the boundary currents east of Madagascar, near 12°S at Cape Amber where the mean current flows northwestward and near 23°S where the mean current flows approximately southward. Transports derived from the moored current measurements in the depth range 150–1100 m compare reasonably well with those derived from ship sections by Swallow et al. (this issue). At 12°S, very energetic boundary current transport variations occur in the 40- to 55-day-period band, contributing about 40% to the total transport variance, while at 23°S the 40- to 55-day-period band fluctuations contribute only 15% to the total transport variance. The fluctuations near 12°S do not seem to be caused by local wind forcing, which does not show an energy peak in this period band. A significant annual cycle cannot be detected in the moored current and transport time series despite significant variation of wind forcing over the subtropical Indian Ocean. A comparison of the observations is carried out with two different numerical Indian Ocean models, both forced by the seasonally varying winds of Hellerman and Rosenstein (1983). A reduced-gravity model gives mean boundary current transports which compare well with the observations and also shows a negligible seasonal cycle. The multilayer Geophysical Fluid Dynamics Laboratory model also shows a small seasonal cycle. The observational evidence from the western subtropical Indian Ocean appears to be similar to that from the subtropical North Atlantic east of the Bahamas-Antilles arc where also no significant seasonal boundary current response was detected, despite large annual variation of wind forcing over the ocean. The two observational situations and numerical model results for both oceans are compared.