scholarly journals On the Chandler periodicity (Polar Motion, LOD and Climate)

2000 ◽  
Vol 178 ◽  
pp. 397-402
Author(s):  
F. Buffa ◽  
A. Poma
Keyword(s):  
Time Series ◽  
Polar Motion ◽  
Superconducting Gravimeter ◽  
Spin Axis ◽  
Rainfall Time Series ◽  
Observation Level ◽  
Motion Data ◽  
The Earth ◽  
Chandler Period ◽  
Free Nutation

AbstractThe 14-month Chandler period is associated with the free nutation of the Earth about its spin axis. The observed value of the Chandler period comes usually from the analysis of astronomical series of polar motion data as well as from superconducting gravimeter measurements. At the observation level a periodicity of about 420–440 days also was noticed in microseismic activities. Recently we found evidence of a signal with period similar to the Chandler one in the Sardinia rainfall time series.

Theories of Polar Motion from Tisserand to Poincaré (1890 – 1910)

2000 ◽  
Vol 178 ◽  
pp. 41-66 ◽  
Author(s):  
P. Melchior
Keyword(s):  
Polar Motion ◽  
Scientific Community ◽  
Circular Motion ◽  
Computing Power ◽  
The Earth ◽  
Fixed Pole ◽  
One Year ◽  
Elliptical Motion ◽  
The Impact ◽  
Chandler Period

AbstractThe discovery by Seth C. Chandler (1891) that the motion of the pole (the reality of which had been established by K.F. Küstner and by the simultaneous latitude observations at Honolulu and Berlin by German astronomers) resulted from two components i.e. a free circular motion with a period of 427 days and a forced elliptical motion with a period of 365.25 days, raised considerable interest in the scientific community of astronomers and geophysicists.The celebrated Mécanique Céleste of Tisserand (1890) had been published just one year before at a time when doubts still persisted and arguments could be presented in favor of the fixed pole. Starting with Tisserand’s arguments, we describe in this paper the impact of the successive contributions by A. Greenhill, S. Newcomb, Th. Sloudsky, S. Hough, G. Herglotz, A. Love, J. Larmor and H. Poincaré to the solution of the problems raised by the Chandler period.The lines of reasoning taken by these eminent scientists were rigorously correct so that, after about one hundred years, contemporary researchers, who benefit from a far better knowledge of the inner structure of the Earth and are able to take advantage of modern computing power, do not contradict any of their conclusions and instead refine them with an accuracy which was not imaginable one century ago.

scholarly journals Excitation of the Chandler Wobble

2000 ◽  
Vol 178 ◽  
pp. 455-462
Author(s):  
N.S. Sidorenkov
Keyword(s):  
Polar Motion ◽  
Southern Oscillation ◽  
World Ocean ◽  
Noise Spectrum ◽  
Chandler Wobble ◽  
The Earth ◽  
The Pacific ◽  
And Shifts ◽  
Chandler Period ◽  
Earth’S Inertia Tensor

AbstractThe redistribution of air and water masses between the Pacific and Indian oceans during the El Niño/Southern oscillation (ENSO) changes the components of the Earth’s inertia tensor and shifts the position of the pole of the Earth’s rotation. The spectrum of the ENSO has components with periods of about 6, 3.6, 2.8, and 2.4 years. These periods are all the multiples of the Chandler period T = 1.2 yr. and the principal period of nutation 18.6 yr. A nonlinear model for the Chandler polar motion has been constructed based on this empirical fact. In this model, the ENSO excites the Chandler polar motion by acting on the Earth at the frequencies of combinative resonance. At the same time, the Chandler polar motion induces a polar tide in the atmosphere and the World Ocean, which orders the ENSO. As a result, the dominant components in the noise spectrum of the ENSO are those with the periods indicated above.

scholarly journals Dissipation and Ellipticity of the Chandler Wobble

2000 ◽  
Vol 178 ◽  
pp. 473-480
Author(s):  
Yaozhong Zhu ◽  
Buxi Gao
Keyword(s):  
Energy Dissipation ◽  
Opposite Direction ◽  
Polar Motion ◽  
Semimajor Axis ◽  
Liquid Core ◽  
Chandler Wobble ◽  
Motion Data ◽  
Pole Tide ◽  
Chandler Period ◽  
Theoretical Results

AbstractThe Chandler wobble, one of the main feature of the Earth’s polar motion, is related to the properties of the mantle and liquid core as well as the mobility of the oceans. The equilibrium pole tide and mantle anelasticity both lengthen the Chandler period, moreover, the former imposes a slight ellipticity on the pole path, and the latter is responsible for the wobble energy dissipation. On the basis of the perturbation principles, we derive the theoretical Qω of the Chandler wobble, assuming that the wobble energy is totally dissipated within the mantle. The theoretical ellipticity and orientation of the semimajor axis of the Chandler wobble path for an anelastic Earth are given. Compared with the results for the elastic Earth, the effect of mantle anelasticity does not change the wobble ellipticity significantly, but slightly changes the orientation of the semimajor axis in the opposite direction. This paper has also proved that the effect of the Earth’s 3-axis feature on the wobble ellipticity is only about 19% of that of the equilibrium pole tide. Analysis of the polar motion data obtained by using modern geodetic techniques shows that the observed ellipticity and orientation of the semimajor axis agree with the theoretical results. We can deduce that the pole tide in the globe should be close to equilibrium.

scholarly journals Search for the 531 day-period wobble signal in the polar motion based on EEMD

2015 ◽  
Vol 2 (2) ◽  
pp. 647-673 ◽  
Author(s):  
H. Ding ◽  
W. B. Shen
Keyword(s):  
Time Series ◽  
Polar Motion ◽  
Superconducting Gravimeter ◽  
Ensemble Empirical Mode Decomposition ◽  
Stationary Time Series ◽  
Analysis Method ◽  
Intrinsic Mode Functions ◽  
Conventional Analysis ◽  
Mode Decomposition ◽  
Empirical Mode Decomposition Method

Abstract. In this study, we use a nonlinear and non-stationary time series analysis method, the ensemble empirical mode decomposition method (EEMD), to analyze the polar motion (PM) time series (EOP C04 series from 1962 to 2013) to find a 531 day-period wobble (531 dW) signal. The 531 dW signal has been found in the early PM seires (1962–1977) while cannot be found in the recent PM seires (1978–2013) using conventional analysis approaches. By the virtue of the demodulation feature of EEMD, the 531 dW can be confirmed to be present in PM based on the differences of the amplitudes and phases between different intrinsic mode functions. Results from three sub-series divided from the EOP C04 series show that the period of the 531 dW is subject to variations, in the range of 530.9–524 d, and its amplitude is also time-dependent (about 2–11 mas). Synthetic tests are carried out to explain why the 531 dW can only be observed in recent 30-years PM time series after using EEMD. The 531 dW is also detected in two longest available superconducting gravimeter (SG) records, which further confirms the presence of the 531 dW. The confirmation of 531 dW existence could be significant in establishing a more reasonable Earth rotation model and may effectively contribute to the prediction of the PM and its mechanism interpretation.

scholarly journals Search for the 531-day-period wobble signal in the polar motion based on EEMD

2015 ◽  
Vol 22 (4) ◽  
pp. 473-484 ◽  
Author(s):  
H. Ding ◽  
W. Shen
Keyword(s):  
Time Series ◽  
Polar Motion ◽  
Superconducting Gravimeter ◽  
Ensemble Empirical Mode Decomposition ◽  
Stationary Time Series ◽  
Analysis Method ◽  
Intrinsic Mode Functions ◽  
Conventional Analysis ◽  
Mode Decomposition ◽  
Empirical Mode Decomposition Method

Abstract. In this study, we use a nonlinear and non-stationary time series analysis method, the ensemble empirical mode decomposition method (EEMD), to analyze the polar motion (PM) time series (EOP C04 series from 1962 to 2013) to find a 531-day-period wobble (531 dW) signal. The 531 dW signal has been found in the early PM series (1962–1977), but cannot be found in the recent PM series (1978–2013) using conventional analysis approaches. By virtue of the demodulation feature of EEMD, the 531 dW can be confirmed to be present in PM based on the differences of the amplitudes and phases between different intrinsic mode functions. Results from three sub-series divided from the EOP C04 series show that the period of the 531 dW is subject to variations, in the range of 530.9–524 days, and its amplitude is also time-dependent (about 2–11 mas). Synthetic tests are carried out to explain why the 531 dW can only be observed in recent 30-year PM time series after using EEMD. The 531 dW is also detected in the two longest available superconducting gravimeter (SG) records, which further confirms the presence of the 531 dW. The confirmation of the 531 dW existence could be significant in establishing a more reasonable Earth rotation model and may effectively contribute to the prediction of the PM and its mechanism interpretation.

scholarly journals The combination of polar motion observations

1988 ◽  
Vol 128 ◽  
pp. 247-255 ◽  
Author(s):  
Clark R. Wilson ◽  
R. O. Vicente
Keyword(s):  
Time Series ◽  
Polar Motion ◽  
Weighted Average ◽  
Satellite Laser Ranging ◽  
Laser Ranging ◽  
Short Time Series ◽  
Motion Data ◽  
Combined Solution ◽  
Short Time

Polar motion data for the period 1981–1985 are used to obtain a combined solution from Doppler, Satellite Laser Ranging, and Astrometric observations. The combined solution is a weighted average of the three series, with weights determined from reported errors which are scaled so that they agree with errors estimated from differences among the various series. The combined solution is effective in removing spurious deviations in the pole path which appear in a single series. However, we also show that estimated errors can be unreliable when derived from short time series, when one series is much less noisy than the others. Thus, a combined solution where weights depend upon estimated errors can yield poor results, and we demonstrate this effect by comparing a combined solution for 1984–85 with the independent IRIS series.

scholarly journals A preliminary nonlinear analysis of the earth's chandler wobble

2000 ◽  
Vol 4 (1) ◽  
pp. 39-53 ◽  
Author(s):  
V. Frede ◽  
P. Mazzega
Keyword(s):  
Time Series ◽  
Nonlinear Analysis ◽  
Polar Motion ◽  
Chandler Wobble ◽  
Deterministic Process ◽  
Motion Data ◽  
Predictive Skill ◽  
Lyapunov Spectra ◽  
Global Statistics ◽  
Low Dimensional

The Chandler wobble (CW) is a resonant response of the Earth rotational pole wandering around its figure axis whose excitation mechanism is still uncertain. It appears as polar motion oscillations with an average period of about 433 days and a slowly varying amplitude in the range (0–300) milliarcsec (mas). We here perform a nonlinear analysis of the CW via a time-delay coordinate embedding of its measuredXandYcomponents and show that the CW can be interpreted as a low dimensional unstable deterministic process.In a first step the trend, annual wobble and CW are separated from the raw polar motion data time series spanning the period 1846–1997. The optimal delays as deduced from the average mutual information function are 105 and 115 days for theXandYcomponents respectively. Then from the global statistics of the false neighbours, the embedding dimensionDE=4is estimated for both series. The local dimensionDLcan also be extracted from the time series by testing the predictive skill of local mappings fitted to the embedded data vectors. The resultDL=3is quite robust and corroborate the idea that the CW behaves like a dissipative oscillator driven by a deterministic process. Indeed the orbit reconstructions in pseudo-phase space both draw the figure of a perturbated 1-torus.The computation of the Lyapunov spectra further shows that this torus-like figure is an attractor with a 1D unstable manifold. The theoretical horizons of prediction deduced from the (positive) principal exponents are about 367 and 276 days for theXandYChandler components respectively. Moreover the local Lyapunov exponents exhibit significant variations with maxima (and corresponding losses of predictibility) in the decades 1860–1870 and 1940–1950.

scholarly journals Nature and Properties of the Chandler Motion and Mechanism of its Damping and Excitation

2000 ◽  
Vol 178 ◽  
pp. 447-453 ◽  
Author(s):  
J.M. Ferrándiz ◽  
Yu. V. Barkin
Keyword(s):  
Analytical Solution ◽  
Polar Motion ◽  
The Body ◽  
Lower Envelope ◽  
Meridian Plane ◽  
The Earth ◽  
Deformable Bodies ◽  
Characteristic Behaviour ◽  
Special Approach ◽  
Chandler Period

AbstractThe analytical studies of the Chandler motion of the Earth’s pole on the basis of the special approach to the problem, using the canonical and noncanonical equations in the Andoyer elastic variables (Barkin, et al. 1995; Barkin, 1996; in press) have been fulfilled. The Earth is considered as an isolated celestial body with the anelastic (in general case) external envelope (the mantle) and an invariant central part (the core).The interpretation of the Chandler motion of the body, deformed by its own rotation, was given in the case of an elastic envelope. It was shown that the body rotates as a fictitious rigid body with different moments of inertia. The analytical solution of the problem let us explain the next properties of the motion of the deformable bodies: 1) observed period of the Earth’s polar motion; 2) ellipticity of the pole trajectory and difference of the eccentricities of the Chandler and Euler motions; 3) nonuniform velocity of the counter-clockwise polar motion along the Chandler ellipse; 4) orientation of this ellipse (its minor axis is located in the meridian plane, at 14.5 W degrees).The influence of the dissipation on the damping of the Chandler polar motion was studied. The analytical solution of the problem was obtained for the simplest treatment of the delay of the tides caused by the Earth’s rotation (Getino & Ferrándiz 1991; Kubo, 1991). This model explains the characteristic behaviour of the amplitude of the Chandler motion in the periods 1905–1920, 1943–1960 (Vondrák, & Cyril, 1966). The excitation of the Chandler motion can be explained by the upper and lower envelope displacements (Barkin, 1999) with Moon-Sun forced attraction with a period of 412 days, close to the Chandler period.

scholarly journals Is the Chandler Period Stable?

1993 ◽  
Vol 156 ◽  
pp. 303-308
Author(s):  
Gao Buxi
Keyword(s):  
Fourier Transform ◽  
Polar Motion ◽  
Chandler Wobble ◽  
Deconvolution Method ◽  
Motion Data ◽  
Probable Explanation ◽  
Equilibrium Response ◽  
Chandler Period ◽  
Non Equilibrium

The problem on Chandler period is an unsolved one. Several authors suggested a hypothesis that the Chandler wobble is only one free period which slightly changes in time and is amplitude-dependent. In this paper we shall make the hypothesis more rigorous than that has been carried yet. A new deconvolution method for Fourier transform is suggested. Using this method the polar motion data are analysed. The analysis results are shown; the Chandler period is not stable and is indeed amplitude-dependent. The probable explanation for the amplitude-dependent of Chandler period is that, which might be caused by non-equilibrium response of the ocean.

Reference Coordinate System Requirements for Geophysics

1975 ◽  
Vol 26 ◽  
pp. 87-92
Author(s):  
P. L. Bender
Keyword(s):  
Coordinate System ◽  
Polar Motion ◽  
Main Part ◽  
Measurement Techniques ◽  
Reference Points ◽  
Angular Motion ◽  
Coordinate Systems ◽  
Axis Of Rotation ◽  
The Earth ◽  
Fixed System

AbstractFive important geodynamical quantities which are closely linked are: 1) motions of points on the Earth’s surface; 2)polar motion; 3) changes in UT1-UTC; 4) nutation; and 5) motion of the geocenter. For each of these we expect to achieve measurements in the near future which have an accuracy of 1 to 3 cm or 0.3 to 1 milliarcsec.From a metrological point of view, one can say simply: “Measure each quantity against whichever coordinate system you can make the most accurate measurements with respect to”. I believe that this statement should serve as a guiding principle for the recommendations of the colloquium. However, it also is important that the coordinate systems help to provide a clear separation between the different phenomena of interest, and correspond closely to the conceptual definitions in terms of which geophysicists think about the phenomena.In any discussion of angular motion in space, both a “body-fixed” system and a “space-fixed” system are used. Some relevant types of coordinate systems, reference directions, or reference points which have been considered are: 1) celestial systems based on optical star catalogs, distant galaxies, radio source catalogs, or the Moon and inner planets; 2) the Earth’s axis of rotation, which defines a line through the Earth as well as a celestial reference direction; 3) the geocenter; and 4) “quasi-Earth-fixed” coordinate systems.When a geophysicists discusses UT1 and polar motion, he usually is thinking of the angular motion of the main part of the mantle with respect to an inertial frame and to the direction of the spin axis. Since the velocities of relative motion in most of the mantle are expectd to be extremely small, even if “substantial” deep convection is occurring, the conceptual “quasi-Earth-fixed” reference frame seems well defined. Methods for realizing a close approximation to this frame fortunately exist. Hopefully, this colloquium will recommend procedures for establishing and maintaining such a system for use in geodynamics. Motion of points on the Earth’s surface and of the geocenter can be measured against such a system with the full accuracy of the new techniques.The situation with respect to celestial reference frames is different. The various measurement techniques give changes in the orientation of the Earth, relative to different systems, so that we would like to know the relative motions of the systems in order to compare the results. However, there does not appear to be a need for defining any new system. Subjective figures of merit for the various system dependon both the accuracy with which measurements can be made against them and the degree to which they can be related to inertial systems.The main coordinate system requirement related to the 5 geodynamic quantities discussed in this talk is thus for the establishment and maintenance of a “quasi-Earth-fixed” coordinate system which closely approximates the motion of the main part of the mantle. Changes in the orientation of this system with respect to the various celestial systems can be determined by both the new and the conventional techniques, provided that some knowledge of changes in the local vertical is available. Changes in the axis of rotation and in the geocenter with respect to this system also can be obtained, as well as measurements of nutation.

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