Further study of a jet stream‐generated Kelvin‐Helmholtz instability
Further study of a jet stream‐generated Kelvin‐Helmholtz instability
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急流产生的开尔文-亥姆霍兹不稳定性的进一步研究
DOI：
10.1029/jc086ic07p06631
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发表时间：
1981
影响因子：
--
通讯作者：
R. Rüster
中科院分区：
文献类型：
--
作者：
J. Klostermeyer;R. Rüster
高分辨率VHF多普勒雷达测量在急流通道揭示径向速度振荡产生的开尔文-亥姆霍兹（KH）不稳定性。利用数字滤波器和最小二乘法对速度数据进行了详细的研究，结果表明，KH振荡的增长率随着时间的增加而线性降低，因此可以定义增长阶段和衰减阶段。在KHI发生期间，雷达信号功率表现为高于平均功率水平20 dB的周期性爆发。爆发的周期等于KH振荡的周期，并且被限制在产生KH不稳定性的临界水平附近的高度。模型计算表明，能量爆发是由kh诱导的超绝热递减率引起的静态不稳定性产生的。在生长阶段，平均风的垂直廓线表现出特征性的时间变化，这可能归因于KH不稳定的雷诺兹应力。有一些证据表明，观测到的KH振荡是由长周期重力波引发的KH波序列的一部分。
High-resolution VHF Doppler radar measurements during a jet stream passage reveal radial velocity oscillations produced by a Kelvin-Helmholtz (KH) instability. A detailed investigation of the velocity data, using digital filters and least squares methods, shows that the growth rate of the KH oscillations decreases linearly with increasing time so that a growth and a decay stage can be defined. During the occurrence of the KHI, the radar signal power is characterized by periodic bursts up to 20 dB above the mean power level. The bursts have a period equal to that of the KH oscillation and are restricted to heights around the critical level at which the KH instability is generated. Model computations indicate that the power bursts are produced by static instabilities which are due to KH-induced superadiabatic lapse rates. During the growth stage, the vertical profile of the mean wind exhibits characteristic temporal changes that can probably be ascribed to the Reynolds stress of the KH instability. There is some evidence that the observed KH oscillations are parts of a sequence of KH waves initiated by long-period gravity waves.