Modeling the initial , fast Sea-Surface Height decay of Agulhas ring ‘ ‘ Astrid ’ ’
Modeling the initial , fast Sea-Surface Height decay of Agulhas ring ‘ ‘ Astrid ’ ’
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模拟厄加勒斯环“阿斯特丽德”初始快速海面高度衰减
DOI：
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发表时间：
2002
期刊：
影响因子：
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通讯作者：
C. Vethc
中科院分区：
文献类型：
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作者：
S. S. Drijfhouta;C. A. Katsmanb;L. D. Steurb;P. C. F. V. D. Vaartb;P. J. V. Leeuwenb;C. Vethc
本文利用在第一次MARE巡航期间测得的环Astrid的圆对称、等效正压理想化，研究了厄古拉斯环的早期海面高度（SSH）衰减。观测表明，阿古拉斯环的SSH在脱落后衰减最快。结果表明，观测到的Astrid环的初始快速衰减可以通过数值模式恢复，而SSH的衰减主要是斜压/正压混合不稳定造成的。此外，还进行了一系列数值试验，研究了环强度、正压分量、直径、径向廓线、B和冷却的衰减。在所讨论的所有情况下，环都对m 1/4 2模线性不稳定。前10天的演变很好地预测了线性稳定性分析。m 1/4 2模的进一步增长在大多数情况下会导致环的分裂。SSH衰变的环是与转换的母环的可用势能的近正压高模态的动能。大部分的能量释放与m 1/4 2模有关。同时，母环的正压能量向斜压能量转换。与共转环相关的强正压分量是SSH衰减发生的必要条件。反旋环的特征可能是斜压分量向正压分量的能量转换使SSH增加。对于共转环，当不稳定性发展得不那么剧烈时，SSH衰变变得较弱。环Astrid的模拟表明，示踪剂从核心的比例与SSH的衰减损失。在温跃层中，流体的相关混合优选地发生在伸长环的末端。在最深的层次上，混合与通过Rossby波辐射的色散有关。r 2002爱思唯尔科技有限公司。保留所有权利。
The early Sea-Surface Height (SSH) decay of an Agulhas ring is studied using a circular symmetric, equivalent barotropic idealization of ring Astrid, which was measured during the first MARE-cruise. Observations indicate that the SSH of Agulhas rings most rapidly decays just after shedding. It is found that the observed initial fast decay of ring Astrid can be recovered by a numerical model and that a mixed baroclinic/barotropic instability accounts for most of the observed decay of SSH. In addition, a series of numerical experiments is presented in which the effects on the decay of ring strength, barotropic component, diameter, radial profile, b; and cooling were investigated. In all cases discussed, rings are linearly unstable to an m 1⁄4 2 mode. The evolution of the first 10 days is well predicted by a linear stability analysis. Further growth of the m 1⁄4 2 mode leads in most cases to split-up of the ring. The SSH decay of the rings is associated with a conversion from available potential energy of the parent ring to kinetic energy of nearly barotropic higher modes. Most of the energy release is associated with the m 1⁄4 2 mode. Also, the parent ring features an energy conversion from its barotropic to its baroclinic components. A strong barotropic component associated with a corotating ring is essential for SSH decay to occur. Counterrotating rings may feature SSH increase by energy conversion from the baroclinic to the barotropic component. For corotating rings SSH decay becomes weaker when the instability develops less vigorous. The simulation of ring Astrid shows that tracer loss from the core scales well with the decay of SSH. In the thermocline the associated mixing of fluid occurs preferably at the extremes of the elongating ring. At the deepest levels mixing is associated with dispersion through Rossby-wave radiation. r 2002 Elsevier Science Ltd. All rights reserved.