Consistent atmospheric and oceanic excitation of the Earth's free polar motion
Consistent atmospheric and oceanic excitation of the Earth's free polar motion
复制标题
地球自由极移的一致大气和海洋激发
DOI：
10.1111/j.1365-246x.2004.02208.x
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发表时间：
2004
影响因子：
2.8
通讯作者：
Maik Thomas
中科院分区：
文献类型：
--
作者：
F. Seitz;J. Stuck;Maik Thomas
通过空间大地测量技术观测到的地球定向参数显示出一系列广泛的频率。人们已经做了许多努力，将光谱峰值与地球物理过程（如大气或海洋变化）联系起来。然而，一些典型振荡的激发机制仍然不清楚。为了深入了解地球的自转动力学，DGFI（Deutsches Geodatisches Forschungsinstitut）开发了地球自转和重力的非线性陀螺动力学模型（DyMEG）。本文研究了大气和海洋激励对粘弹性陀螺自由旋转的叠加效应。与以往的研究不同，地球自由摆动（钱德勒摆动）的周期和阻尼是由陀螺仪的几何和流变参数产生的。在时域中的极移的数值结果表明，DyMEG创建一个阻尼振荡的地球物理和重力激励的情况下。当考虑大气和海洋角动量时，阻尼消失。模拟的1975 ~ 1994年在一致的大气和海洋角动量强迫下的极移与大地测量观测结果有很好的相关性，这表明自由陀螺模式DyMEG能够真实地再现地球自转的变化。对大气和海洋激发的光谱分析没有显示出钱德勒频带中功率增加的迹象，因为在最近的研究中，它被认为是维持钱德勒摆动的原因。因此，随机信号的气候动态所造成的天气和海洋质量的再分布被认为是一个足够的来源，以保持振幅的地球的自由摆动的共振相互作用。
SUMMARY Earth orientation parameters as observed by space-geodetic techniques show a broad spectrum of frequencies. Many efforts have been made to relate spectral peaks to geophysical processes, such as atmospheric or oceanic variations. However, the mechanisms of excitation of some typical oscillations are still unclear. In order to gain insight into the rotational dynamics of the Earth, the non-linear gyroscopic Dynamic Model for Earth Rotation and Gravity (DyMEG) has been developed at DGFI (Deutsches Geodatisches Forschungsinstitut). The present paper studies the superposed effect of atmospheric and oceanic excitation on the free rotation of a viscoelastic gyro. In contrast to former investigations, period and damping of the Earth's free wobble (Chandler wobble) are generated by the gyro from geometrical and rheological parameters. Numerical results for polar motion in the time domain demonstrate that DyMEG creates a damped oscillation in absence of geophysical and gravitational excitations. Damping vanishes when atmospheric and oceanic angular momentum is regarded. Simulated polar mo- tion for the period from 1975 to 1994 forced by consistent atmospheric and oceanic angular momentum shows significant correlation with geodetic observations, which indicates that the free gyroscopic model DyMEG is able to reproduce realistic variations of the Earth's rotation. Spectral analyses of both atmospheric and oceanic excitations give no hint for increased power in the Chandler frequency band as it was stated for the maintenance of the Chandler wobble in recent research studies. Thus, stochastic signals in the climate dynamics as caused by both the weather and oceanic mass redistributions are found to be a sufficient source to maintain the amplitude of the Earth's free wobble by resonant interaction.