Chandler摆动的双频现象用于拟合极移确定项的研究

极移中Chandler摆动出现的双频现象,一直以来为许多学者所关注。推导了基于Chandler摆动双频的极移确定项模型,并采用该模型对极移确定项进行了拟合。与仅采用单频进行确定项拟合的对比表明,利用双频能取得更理想的结果。     

用极移数据直接测算钱德勒摆动Q值

运用已经发展起来的共振激发和参数共振模型,在频率调制的基础上,对IERS极移数据测算出钱德勒摆动的Q值,得到平均值为63,并以每百年0.8的速率在增大。这一结果与Q的滞弹性PREM模型理论值69十分接近,表明共振激发模型和参数共振模型完全与钱德勒摆动滞弹理论相容。     

Chandler摆动轨迹的非线性螺旋线拟合及机制的研究

依照非线性动力学原理,从摆动的不稳定性出发,推出Ｃｈａｎｄｌｅｒ摆动的非线性动力学螺旋运动轨迹模型。给出Ｃｈａｎｄｌｅｒ摆动的非线性动力学螺旋轨迹解法,由ＩＥＲＳ实测数据中的Ｃｈａｎｄｌｅｒ摆动位移坐标值,可以得到每个数据间的螺线插值参数。这对于以往的线性插值的折线拟合是一个改进,也为Ｃｈａｎｄｌｅｒ摆动的螺旋运动轨迹给出了理论解释。计算得到,Ｃｈａｎｄｌｅｒ摆动平均每平螺旋的螺距有６．７５ｍａｓ。     

基于LS+AR模型的极移预报及其周期项影响分析

采用LS+AR预报模型的对极移进行预报,深入分析极移数据中钱德勒项和周年项对预报精度的影响。计算结果显示,极移数据中各周期项具有时变性特点,将已知观测数据确定出的周期项应用到极移预报中会明显提高预报精度。因此,建议在进行极移预报之前首先应进行时间序列分析,确定已有数据的各周期项,在极移预报中加以考虑。     

Chandler摆动轨迹的非线性螺旋线拟合及机制的研究

依照非线性动力学原理,从摆动的不稳定性出发,推出Chandler摆动的非线性动力学螺旋运动轨迹模型。给出Chandler摆动的非线性动力学螺旋轨迹解法,由IERS实测数据中的Chandler摆动位移坐标值,可以得到每两个数据间的螺线插值参数。这对于以往的线性插值的折线拟合是一个改进,也为Chandler摆动的螺旋运动轨迹给出了理论解释。计算得到,Chandler摆动平均每年螺旋的螺距有6.75mas。     

对钱德勒参数进行时变修正的CLS+AR模型在极移预测中的应用

根据LS模型参数中钱德勒项的时变性质,提出了基于钱德勒参数时变修正的CLS模型,并用CLS+AR对极移进行预测。实验结果表明,CLS+AR模型在极移预测精度上较LS+AR模型有较大改善。     

Polar motion modeling,analysis, and prediction with time dependent harmonic coefficients

A time dependent amplitude model was proposed for the analysis and prediction of polar motion time series. The formulation was implemented to analyze part of the new combined solution, EOP (IERS) C 04, daily polar motion time series of 14 years length using a statistical model with first order autoregressive disturbances. A new solution approach, where the serial correlations of the disturbances are eliminated by sequentially differencing the measurements, was used to estimate the model parameters using weighted least squares. The new model parsimoniously represents the 14-year time series with 0.5 mas rms fit, close to the reported 0.1 mas observed pole position precisions for the x and y components. The model can also predict 6 months into the future with less than 4 mas rms prediction error for both polar motion components, and down to sub mas for one-step ahead prediction as validated using a set of daily time series data that are not used in the estimation. This study is dedicated to the memory of Prof. Urho Uotila (1923–2006) whose teaching of “Adjustment Computations” over the years influenced so much, so many of us who had the privilege of being his students.     

三轴地球Chandler晃动的振幅-频率调制机制

研究了三轴地球的自由晃动,给出了Euler动力学方程的椭圆函数解和Euler/Chandler周期。研究表明,三轴性使得极移轨迹变为短、长半轴分别与主惯性轴A、B平行的椭圆,同时使得极移和自转速率产生耦合效应,导致Chandler晃动的振幅-频率调制机制。根据IERS数据还得出了地极正以3.93 mas/a的速率向77.98°W方向漂移的结论。     

Atmospheric excitation of polar motion

The polar motion excited by the fluctuation of global atmospheric angular momentum (AAM) is investigated. Based on the global AAM data, numerical results demonstrate that the fluctuation of AAM can excite the seasonal wobbles (e.g., the 18-month wobble) and the Chandler wobble, which agree well with previous studies. In addition, by filtering the dominant low frequency components, some distinct polar wobbles corresponding to some great diurnal and semi-diurnal atmospheric tides are found.     

Atmospheric excitation of polar motion

The polar motion excited by the fluctuation of global atmospheric angular momentum (AAM) is investigated. Based on the global AAM data, numerical results demonstrate that the fluctuation of AAM can excite the seasonal wobbles (e.g., the 18-month wobble) and the Chandler wobble, which agree well with previous studies. In addition, by filtering the dominant low frequency components, some distinct polar wobbles corresponding to some great diurnal and semi-diurnal atmospheric tides are found.     

Linear drift and periodic variations observed in long time series of polar motion

 Two long time series were analysed: the C01 series of the International Earth Rotation Service and the pole series obtained by re-analysis of the classical astronomical observations using the HIPPARCOS reference frame. The linear drift of the pole was determined to be 3.31 ± 0.05 milliarcseconds/year towards 76.1 ± 0.80° west longitude. For the least-squares fit the a priori correlations between simultaneous pole coordinates x _p , y _p were taken into account, and the weighting function was calculated by estimating empirical variance components. The decadal variations of the pole path were investigated by Fourier and wavelet analysis. Using sliding windows, the periods and amplitudes of the Chandler wobble and annual wobble were determined. Typical periods in the variable Chandler wobble and annual wobble parameters were obtained from wavelet analyses. Received: 21 January 2000 / Accepted: 28 August 2000     

利用LS_AR模型对极移参数的中长期预报

为了满足深空探测器自主导航定位对极移参数中长期预报的需求,阐述了基于LS_AR模型的极移参数中长期预报和精度评定的原理,提出了4种改进方案对LS_AR模型的构建进行优化,并利用IERS提供的1990～1996年的极移参数的时间序列检验4种优化方案,得到了最优的预报模型,在400 d跨度上,其预报结果的平均绝对误差比未优化的模型小3 mas左右。