Seasonal and inter-annual variations of length of day and polar motion observed by SLR in 1993―2006 |
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基金项目: | Supported by the International S&T Cooperation Program of China (Grant No. 2006DFA21980), Hi-Tech Research and Development Program of China (Grant No. 2006AA12z303) and National Natural Science Foundation of China (Grant No. 40774009) |
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摘 要: | A time series of length of the day (LOD) and polar motion (PM) were estimated from the range data measured by the satellite laser ranging technique (SLR) to LAGEOS 1/2 through 1993 to 2006. Compared with EOPC04 released by the International Earth Rotation and Reference Systems Service (IERS), the root mean squares errors for LOD, X and Y of PM are 0.0067 milliseconds (ms), 0.18 milli-arc-sec- onds (mas) and 0.20 mas, respectively. Then the time series are analyzed with the wavelet transformation and least squares method. Wavelet analysis shows that there are the obvious seasonal and inter- annual variations of LOD and PM, but the annual variation cannot be distinguished from the Chandler variation because these two frequencies are very close. The trends and periodic variations of LOD and PM are given in the least squares sense. LOD changes with the annual and semiannual periods. The annual and Chandler variations for PM are also detected, but the semiannual motion for PM is not found. The trend rate of the LOD change in 1993―2006 is ?0.18 ms per year, and the difference from the well- known 1.7 ms per century showed that the trend rate is diverse in different periods possibly. The trend rates of PM in the X and Y directions are 2.25 and 1.67 mas per year respectively, and the North Pole moves to 36.5°E relative to the crust, which is different from the direction of Greenland.
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收稿时间: | 2008-05-20 |
修稿时间: | 2008-09-08 |
Seasonal and inter-annual variations of length of day and polar motion observed by SLR in 1993–2006 |
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Authors: | JinYun Guo YanBen Han |
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Affiliation: | (1) National Astronomical Observatories, Chinese Academy of Sciences, Beijing, 100012, China;(2) College of Geodesy and Geomatics, Shandong University of Science and Technology, Qingdao, 266510, China |
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Abstract: | A time series of length of the day (LOD) and polar motion (PM) were estimated from the range data measured by the satellite
laser ranging technique (SLR) to LAGEOS 1/2 through 1993 to 2006. Compared with EOPC04 released by the International Earth
Rotation and Reference Systems Service (IERS), the root mean squares errors for LOD, X and Y of PM are 0.0067 milliseconds
(ms), 0.18 milli-arc-seconds (mas) and 0.20 mas, respectively. Then the time series are analyzed with the wavelet transformation
and least squares method. Wavelet analysis shows that there are the obvious seasonal and inter-annual variations of LOD and
PM, but the annual variation cannot be distinguished from the Chandler variation because these two frequencies are very close.
The trends and periodic variations of LOD and PM are given in the least squares sense. LOD changes with the annual and semiannual
periods. The annual and Chandler variations for PM are also detected, but the semiannual motion for PM is not found. The trend
rate of the LOD change in 1993–2006 is −0.18 ms per year, and the difference from the well-known 1.7 ms per century showed
that the trend rate is diverse in different periods possibly. The trend rates of PM in the X and Y directions are 2.25 and 1.67 mas per year respectively, and the North Pole moves to 36.5°E relative to the crust, which is
different from the direction of Greenland.
Supported by the International S&T Cooperation Program of China (Grant No. 2006DFA21980), Hi-Tech Research and Development
Program of China (Grant No. 2006AA12z303) and National Natural Science Foundation of China (Grant No. 40774009) |
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Keywords: | satellite laser ranging (SLR) length of day polar motion Earth rotation wavelet transformation |
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