An analysis of the homogeneous ILS polar motion series

Wilson, Clark R.; Vicente, R. O.

doi:10.1111/j.1365-246x.1980.tb02594.x

Cited by 98 publications

(51 citation statements)

References 6 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Our preferred value of F is that from EOP93C010092, the longest series which is reasonably homogeneous. The value obtained (0.8433 _+ 0.003 cpy) equivalent to a period of (433.1 mean solar days (msd) +__ 1.7 msd) is fully consistent with the results reported previously by Wilson and Vicente [1980, 1981, 1990] for the ILS series, which comprises a subset of the data used to obtain EOP93CO1. procedures which are not fully consistent.…”

Section: All Estimates Of F Insupporting

confidence: 76%

On the variability of the Chandler frequency

Vicente¹,

Wilson²

1997

J. Geophys. Res.

Self Cite

View full text Add to dashboard Cite

Abstract. We have estimated the Chandler frequency from a variety of polar motion time series derived from optical and space geodetic data which span various time periods from 1846 through the early 1990s. Estimates of F vary, depending upon which time series is employed, but the variation is not significant when associated intervals of confidence are considered; thus there is no evidence that the true Chandler frequency has varied. Using a maximum likelihood method, our preferred estimate of F is 0.8433 cycles per tropical year (cpy), _+0.003 cpy, or equivalently a period of 433.1 mean solar days (msd), _+ 1.7 msd. Estimates are given on the condition that the Gaussian statistical model of the excitation process is valid, and new approaches which employ observations of the polar motion excitation process should eventually provide better estimates, which may differ from those determined here. IntroductionThe theory of the motion of the Earth around its center of mass is developed in such a way that the motion is separated into two distinct parts which affect the terrestrial and celestial coordinates in different ways. The first of these is a free motion, which exists independently of external forces. Originally There are two issues to resolve when examining whether variability in estimates of F should be interpreted as variability in F. In the first place, the analysis is only meaningful when the component is above the noise level in the data. This condition is met in the case of the Chandler wobble, with a signal amplitude of a few hundred milli arc seconds (mas) and noise levels ranging from 10 mas or more in older optical data to below 1 mas in recent space geodetic data. The second issue is the adoption of an estimation technique firmly tied to the physical aspects of the problem that can provide meaningful statements of confidence, taking into consideration uncertainty introduced by both noise and the finite duration of the data set. The analysis method in this paper, based on the maximum likelihood principle described by Jeffreys [1940, 1968], meets these requirements, as discussed in section 3. 20,439

show abstract

Section: All Estimates Of F Insupporting

confidence: 76%

On the variability of the Chandler frequency

Vicente¹,

Wilson²

1997

J. Geophys. Res.

Self Cite

View full text Add to dashboard Cite

show abstract

“…Markowitz was the first to report the existence of an oscillation in polar motion having a period of about 24 years (Markowitz 1960), hence, this wobble is referred to as the Markowitz wobble. Further studies aimed at estimating its parameters have been made; see, e.g., Wilson and Vicente (1980), Dickman (1981), Okamoto and Kikuchi (1983) and, for a review, Poma (2000). Compared to the previous estimates for the Markowitz wobble, our results re-confirm that there exists such a wobble with a period length of about 30 years, but smaller in its amplitude (semi-major axis) at a direction of about 15…”

Section: Discussion Of the Resultsmentioning

confidence: 99%

Low-Frequency Variations, Chandler and Annual Wobbles of Polar Motion as Observed Over One Century

Höpfner

2004

Surveys in Geophysics

View full text Add to dashboard Cite

Abstract. Polar motion data is available from the mid-19th century to the present. Based on time series with a variety of sampling intervals (monthly, 0.05-year, 5-day and daily), we have separated the low-frequency terms by low-pass filtering and the Chandler and annual terms by recursive band-pass filtering of the pole coordinates. Using a simple unweighted least-squares fit to the filtered low-frequency terms, the linear trends of the rotation pole were estimated. Assessing the estimates based on intercomparisons, the most reliable trend estimate was found. Using a Fast Fourier Transform, we have computed the prograde, retrograde and total amplitude spectra of the low-frequency part of polar motion in order to reveal the long-periodic signals. The characteristics and time evolution of the Chandler and annual wobbles are described by changes in their parameters (radii, directions and period lengths) over one century.

show abstract

“…All ILS latitude observations have been reanalysed and combined to the PM solution within a consistent system for the period 1899. .0 by Yumi and Yokoyama (1980). Based on optical astrometry observations, a PM time series for the period 1899.7-1992.0 was obtained from a re-analysis within the Hipparcos frame by Vondrák et al (1998).…”

Section: Introductionmentioning

confidence: 99%

“…Using latitude variations observed at 20 stations (5 ILS and 15 independent stations) between 1900 to 1970 and 1900 to 1980, the properties of the Chandler wobble including amplitude, phase and ellipticity were derived by Guinot (1972Guinot ( , 1982. An analysis of the homogeneous ILS time series for the period 1899-1977 made by Wilson and Vicente (1980) was concerned with annual, Chandler and long-period motions of the Earth's pole. Dickman (1981) also studied these terms using the homogeneous ILS time series from 1899.9-1979.0, with a focus on controversial PM features apparently possessed by the older ILS data.…”

Section: Introductionmentioning

confidence: 99%

Chandler and annual wobbles based on space-geodetic measurements

Höpfner¹

2003

Journal of Geodynamics

View full text Add to dashboard Cite

Abstract. In this study, we examine the major components of polar motion, focusing on quantifying their temporal variability. In particular, by using the combined Earth orientation series SPACE99 computed by the Jet Propulsion Laboratory (JPL) from 1976 to 2000 at daily intervals, the Chandler and annual wobbles are separated by recursive band-pass filtering of the ¢ ¡ ¤ £ and ¦ ¥ § £ components. Then, for the trigonometric, exponential, and elliptic forms of representation, the parameters including their uncertainties are computed at epochs using quarterly sampling. The characteristics and temporal evolution of the wobbles are presented, as well as a summary of estimates of different parameters for four epochs.

show abstract

An analysis of the homogeneous ILS polar motion series

Cited by 98 publications

References 6 publications

On the variability of the Chandler frequency

On the variability of the Chandler frequency

Low-Frequency Variations, Chandler and Annual Wobbles of Polar Motion as Observed Over One Century

Chandler and annual wobbles based on space-geodetic measurements

Contact Info

Product

Resources

About