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1.
The superconducting gravimeter (SG) TT70 has been continuously recording gravity data at the GeoForschungsZentrum (GFZ) Potsdam
absolute gravity site since July 1992. The recorded data are edited and preprocessed by spike and step detection and elimination
and gap filling. An atmospheric pressure correction is carried out on gravity data in the time domain with a complex admittance
before tidal fitting. The atmospheric pressure admittance is calculated from tide free output of SG data and local atmospheric
pressure using the cross spectral method. The ground water level admittance is determined by a single coefficient. Improvements
with these corrections are shown in analysis results.
New tidal parameters for Potsdam site are determined and compared with recordings of an Askania spring gravimeter at a nearby
site. Deviations against the Wahr-Dehant-model are shown.
Polar motion data of the IERS (International Earth Rotation Service, Paris) are used to calculate variations of centrifugal
acceleration caused by polar motion (pole tide). These are compared with the corrected tide free output of SG series. For
drift determination the polar motion correction is applied on SG data.
The nutation period equivalent to the Earth's Nearly Diurnal Free Wobble is calculated from the SG data with a value of TFCN = (437.4 ± 1.5) sidereal days. This result is compared with those obtained from other SG stations.
Received 19 December 1995; Accepted 13 September 1996 相似文献
2.
Precise tidal gravity recorded with superconducting gravimeters at stations Wuhan (China) and Kyoto (Japan) 总被引:9,自引:0,他引:9
Three long series of tidal gravity observations, totalizing approximately 24 years and recorded with three superconducting
gravimeters, T004, T008, and T009, at stations Wuhan (China) and Kyoto (Japan), are studied. The tidal amplitude factors and
phase differences are determined precisely using Eterna and Nsv techniques. The precision of the main tidal amplitudes is
at the same level of 0.01 μGal. The atmospheric gravity signals are corrected using the coefficients determined with a regression
method between tidal gravity residual and station air pressure. The oceanic gravity signals are modeled based on five global
oceanic models. It is found that the oceanic models developed by the analysis of measurements from Topex/Poseidon altimeters
have the best fit to the superconducting gravimeter measurements, since the observed residuals and the discrepancies between
the amplitude factors and the theoretical tidal models are reduced more significantly. The long-period gravity variations
are dominated by the non-linear drift phenomena of the instruments, and the short-term variations in gravity are due to the
background noise at the stations.
Received: 20 January 2000 / Accepted: 15 September 2000 相似文献
3.
Five separate polar motion series are examined in order to understand what portion of their variations at periods exceeding
several years represents true polar motion. The data since the development of space-geodetic techniques (by themselves insufficient
for study of long-period motion), and a variety of historical astrometric data sets, allow the following tentative conclusions:
retrograde long-period polar motion below about −0.2 cpy (cycles per year) in pre-space-geodetic data (pre-1976) is dominantly
noise. For 1976–1992, there is poor agreement between space-geodetic and astrometric series over the range −0.2 to +0.2 cpy,
demonstrating that classical astrometry lacked the precision to monitor polar motion in this frequency range. It is concluded
that all the pre-1976 astrometric polar motion data are likely to be dominated by noise at periods exceeding about 10 years.
The exception to this is possibly a linear trend found in some astrometric and space geodetic series. At frequencies above
prograde +0.2 cpy (periods shorter than about 5 years), historical astrometric data may be of sufficient quality for comparisons
with geophysical excitation time series. Even in the era of space geodesy, significant differences are found in long-period
variations in published polar motion time series.
Received: 27 March 2001 / Accepted: 15 October 2001 相似文献
4.
大气压力变化对武汉台站重力场观测的影响 总被引:2,自引:0,他引:2
利用全球2°×2.5°、中国及邻区域30′×30′ 气压资料和Farrell弹性地球模型负荷理论,采用数值积分方法,计算了大气压力变化对武汉台站重力场观测的影响。对1990年1月1日至12月31日的数值结果分析表明,全球大气压力变化对武汉台站重力的影响峰对峰达12微伽,大气重力导纳的年平均值为-0.260 μGal/mba(1 mba=1 hPa),这一结果同潮汐分析中由回归分析方法获得的导纳值相近。说明在利用超导重力仪观测资料应用于地球动力学研究之前,有必要作精细的全球气压变化改正。 相似文献
5.
A study of gravity variations caused by polar motion using superconducting gravimeter data from the GGP network 总被引:8,自引:0,他引:8
Long-term continuous gravity observations, recorded at five superconducting gravimeter (SG) stations in the Global Geodynamic Project (GGP) network, as well as data on orientation variations in the Earths rotation axis (i.e. polar motion), have been used to investigate the characteristics of gravity variations on the Earths surface caused by polar motion. All the SG gravity data sets were pre-processed using identical techniques to remove the luni-solar gravity tides, the long-term trends of the instrumental drift, and the effects of atmospheric pressure. The analysis indicates that the spectral peaks, related to the Chandler and annual wobbles, were identified in both the power and product spectral density estimates. The magnitude of gravity variations, as well as the gravimetric amplitude factor associated with the Chandler wobble, changed significantly at different SG stations and during different observation periods. However, when all the SG observations at these five sites were combined, the gravimetric parameters of the Chandler wobble were retrieved accurately: 1.1613 ± 0.0737 for the amplitude factor and –1°.30 ± 1°.33 for the phase difference. The value of the estimated amplitude factor is in agreement with that predicted theoretically for the zonal tides of an elastic Earth model. 相似文献
6.
Observations of gravity and atmospheric pressure variations during the total solar eclipse of 11 July 1991 in Mexico City
are presented. An LCR-G402 gravimeter equipped with a feedback system and a digital data acquisition system scanned gravity
and pressure every second around the totality. On the pressure record an oscillation, starting at the totality, with a peak
to peak amplitude of 0.5 hPa and a periodicity of 40 to 50 min, can clearly be seen. This oscillation results from the thermal
shock wave produced by the Moon shadow travelling at supersonic speed. At the 0.1 μGal (1 nm · s−2) level all gravity perturbations are explained by the atmospheric pressure effect.
Received: 10 February 1995 / Accepted: 7 June 1996 相似文献
7.
P. Moore 《Journal of Geodesy》1987,61(3):223-234
Starlette was launched in 1975 in order to study temporal variations in the Earth’s gravity field; in particular, tidal and
Earth rotation effects. For the period April 1983 to April 1984 over12,700 normal points of laser ranging data to Starlette have been sub-divided into49 near consecutive 5–6 day arcs. Normal equations for each arc as obtained from a least-squares data reduction procedure, were
solved for ocean tidal parameters along with other geodetic and geodynamic parameters. The tidal parameters are defined relative
to Wahr’s body tides and Wahr’s nutation model and show fair agreement with other satellite derived results and those obtained
from spherical harmonic decomposition of global ocean tidal models. 相似文献
8.
2013-04-20发生在四川芦山的地震,是一个震级为Mw 6.6的高角度逆冲型地震,在2.3~5.3 mHz频段激发了微弱的球型简正模信号。芦山地震的自由振荡信号为人们提供了检验中国大陆超导重力仪高频特性的机会。分析了中国大陆现有的5台超导重力仪和部分宽频带地震仪在芦山地震后的观测数据,结果表明,超导重力仪SG057(拉萨)、SG053(武汉)和流动超导重力仪iGrav(武汉)在2~5 mHz频段具有较低的噪音水平,超导重力仪SG065(武汉)、SG066(丽江)具有较高的噪音水平。 相似文献
9.
A method of analyzing GRACE satellite-to-satellite ranging data is presented which accentuates signals from diurnal ocean
tides and dampens signals from long-period non-tidal phenomena. We form a time series of differences between two independent
monthly mean gravity solutions, one set computed from range-rate data along strictly ascending arcs and the other set computed
from data along descending arcs. The solar and lunisolar diurnal tides having alias periods longer than a few months, such
as K
1, P
1, and S
1, present noticeable variations in the monthly ascending and descending ‘difference’ solutions, while the climate-related
signals are largely cancelled. By computing tidal arguments evaluated along the actual GRACE orbits, we decompose and estimate
residual tidal signals with respect to our adopted prior model GOT4.7. The adjustment in the tidal height is small yet significant,
yielding maximum amplitudes of 4 cm mostly under the Antarctic ice shelves and ~1 cm in general at spatial scales of several
hundred kilometer. Moreover, the results suggest there are possible 1-cm errors in the tide model even over oceans well-covered
by decades of radar altimetry missions. Independent validation of such small adjustments covering wide areas, however, is
difficult, particularly with limited point measurements such as tide gauge. 相似文献
10.
Analysis of the first year of Earth rotation parameters with a sub-daily resolution gained at the CODE processing center of the IGS 总被引:4,自引:4,他引:0
The solutions of the CODE Analysis Center submitted to the IGS, the International Global Position System (GPS) Service for
Geodynamics, are based on three days of observation of about 80–100 stations of the IGS network. The Earth rotation parameters
(ERPs) are assumed to vary linearly over the three days with respect to an a priori model. Continuity at the day boundaries
as well as the continuity of the first derivatives are enforced by constraints. Since early April 1995 CODE has calculated
a new ERP series with an increased time resolution of 2 hours. Again continuity is enforced at the 2-hours-interval boundaries.
The analysis method is described, particularly how to deal with retrograde diurnal terms in the ERP series which may not be estimated with satellite geodetic methods. The results obtained from the first year of data covered by the time series
(time interval from 4 April 1995 to 30 June 1996) are also discussed. The series is relatively homogeneous in the sense of
the used orbit model and the a priori model for the ERPs. The largest source of excitation at daily and sub-daily periods
is likely to be the effect of the ocean tides. There is good agreement between the present results and Topex/Poseidon ocean
tide models, as well as with models based on Very Long Baseline Interferometry (VLBI) and Satellite Laser Ranging (SLR) data.
Non-oceanic periodic variations are also observed in the series. Their origin is most probably a consequence of the GPS solution
strategy; other possible sources are the atmospheric tides.
Received: 13 July 1999 / Accepted: 21 March 2000 相似文献
11.
Earth orientation parameters (EOPs) [polar motion and length of day (LOD), or UT1–UTC] were predicted by artificial neural
networks. EOP series from various sources, e.g. the C04 series from the International Earth Rotation Service and the re-analysis
optical astrometry series based on the HIPPARCOS frame, served for training the neural network for both short-term and long-term
predictions. At first, all effects which can be described by functional models, e.g. effects of the solid Earth tides and
the ocean tides or seasonal atmospheric variations of the EOPs, were removed. Only the differences between the modeled and
the observed EOPs, i.e. the quasi-periodic and irregular variations, were used for training and prediction. The Stuttgart
neural network simulator, which is a very powerful software tool developed at the University of Stuttgart, was applied to
construct and to validate different types of neural networks in order to find the optimal topology of the net, the most economical
learning algorithm and the best procedure to feed the net with data patterns. The results of the prediction were analyzed
and compared with those obtained by other methods. The accuracy of the prediction is equal to or even better than that by
other prediction methods.
Received: 6 February 2001 / Accepted: 23 October 2001 相似文献
12.
The determination of high frequency variations in UT-1 and a component of pole position from a single pass of Doppler observations
of a Navy Navigation Satellite is affected by instrument errors and uncertainties in the gravity field and atmospheric drag
forces used in computing the satellite orbit. For elevation angles above20°, instrument errors contribute about2 msec to the determination of UT-1 and “.03 to the determination of pole position. Gravity and drag errors contribute about 0“.03
of correlated error. But gravity errors may be inferred by statistical analysis of residuuls after drag errors are reduced
by drag-compensating devices aboard future Navy Navigation Satellites. Since20 Doppler stations nominally acquire about100 passes each day, daily observations of UT-1 and pole position could achieve precisions of0.2 msec and “.005, respectively, assuming half the passes contribute to the determination of each component of pole position. The
current accuracy of Doppler results for two day solutions is about50 cm for pole position and1 msec for high frequency variations in UT-1. 相似文献
13.
Contribution of new AAM data source to δLOD excitation 总被引:1,自引:0,他引:1
Data sets of the changes of the length of day (ΔLOD) measured by space geodetic techniques and of the atmospheric angular
momentum (AAM) derived from global meteorological data by the National Meteorological Center (NMC) and the National Centers
for Environmental Prediction/National Center for Atmospheric Research (NCEP/NCAR) are used to reanalyze and study the excitations
of ΔLOD, and to examine and compare the contribution of each AAM series to ΔLOD. The main results are as follows.
1. The AAM reanalyzed with the assimilated global meteorological data by NCEP/NCAR are more accurate and have lower noise
than the original AAM derived by NMC. The NCEP/NCAR-based AAM is more consistent with the changes of the length-of-day series.
2. The NCEP reanalysed AAM data may better explain the non-tidal LOD variations on intraseasonal to interannual time scales,
especially on the quasi-biennial time scale. The atmosphere cannot, however, explain all LOD variations; other excitation
sources are possible.
3. The effects of atmosphere on the estimated values of tides for ΔLOD components up to a month are weak. The preliminary
results of the annual and semiannual tides can be estimated after removing the effects of atmosphere from ΔLOD.
Received: 27 May 1998 / Accepted: 22 March 1999 相似文献
14.
大气负荷响应计算误差估计模型 总被引:1,自引:0,他引:1
罗少聪 《武汉大学学报(信息科学版)》2001,26(3):217-221
用数理统计技术,建立格林函方法计算大气变化引起重力和形焦等效应的精度评定模型,并利用中国及其邻区的大气观,蛭大气误差常数和一个计算方案的精度估计,其结果与固体潮汐检测在不同气候条件下的响应情况相一致,该系统也可应用于格林函数积分形式的其它物理模型的误差估计。 相似文献
15.
Aurore E. Sibois Shailen D. Desai Willy Bertiger Bruce J. Haines 《Journal of Geodesy》2017,91(8):965-983
We present results from the generation of 10-year-long continuous time series of the Earth’s polar motion at 15-min temporal resolution using Global Positioning System ground data. From our results, we infer an overall noise level in our high-rate polar motion time series of 60 \(\upmu \hbox {as}\) (RMS). However, a spectral decomposition of our estimates indicates a noise floor of 4 \(\upmu \hbox {as}\) at periods shorter than 2 days, which enables recovery of diurnal and semidiurnal tidally induced polar motion. We deliberately place no constraints on retrograde diurnal polar motion despite its inherent ambiguity with long-period nutation. With this approach, we are able to resolve damped manifestations of the effects of the diurnal ocean tides on retrograde polar motion. As such, our approach is at least capable of discriminating between a historical background nutation model that excludes the effects of the diurnal ocean tides and modern models that include those effects. To assess the quality of our polar motion solution outside of the retrograde diurnal frequency band, we focus on its capability to recover tidally driven and non-tidal variations manifesting at the ultra-rapid (intra-daily) and rapid (characterized by periods ranging from 2 to 20 days) periods. We find that our best estimates of diurnal and semidiurnal tidally induced polar motion result from an approach that adopts, at the observation level, a reasonable background model of these effects. We also demonstrate that our high-rate polar motion estimates yield similar results to daily-resolved polar motion estimates, and therefore do not compromise the ability to resolve polar motion at periods of 2–20 days. 相似文献
16.
The analysis of lunar laser ranging (LLR) data enables the determination of many parameters of the Earth–Moon system, such
as lunar gravity coefficients, reflector and station coordinates which contribute to the realisation of the International
Terrestrial Reference Frame 2000 (ITRF 2000), Earth orientation parameters [EOPs, which contribute to the global EOP solutions
at the International Earth Rotation Service (IERS)] or quantities which parameterise relativistic effects in the solar system.
The big advantage of LLR is the long time span of lunar observations (1970–2000). The accuracy of the normal points nowadays
is about 1 cm.
The capability of LLR to determine tidal parameters is investigated. In principle, it could be assumed that LLR would contribute
greatly to the investigation of tidal effects, because the Moon is the most important tide-generating body. In this respect
some special topics such as treatment of the permanent tide and the effect of atmospheric loading are addressed and results
for the tidal parameters h
2 and l
2 as well as values for the eight main tides are given.
Received: 14 August 2000 / Accepted: 15 October 2001 相似文献
17.
J. Höpfner 《Journal of Geodesy》2001,75(2-3):137-150
The annual and semiannual residuals derived in the axial angular momentum budget of the solid Earth–atmosphere system reflect
significant signals. They must be caused by further excitation sources. Since, in particular, the contribution for the wind
term from the atmospheric layer between the 10 and 0.3 hPa levels to the seasonal variations in length of day (LOD) is still
missing, it is necessary to extend the top level into the upper stratosphere up to 0.3 hPa. Under the conservation of the
total angular momentum of the entire Earth, variations in the oceanic angular momentum (OAM) and the hydrological angular
momentum (HAM) are further significant excitation sources at seasonal time scales. Focusing on other contributions to the
Earth's axial angular momentum budget, the following data are used in this study: axial atmospheric angular momentum (AAM)
data derived for the 10–0.3 hPa layer from 1991 to 1997 for computing the missing wind effects; axial OAM functions as generated
by oceanic general circulation models (GCMs), namely for the ECHAM3 and the MICOM models, available from 1975 to 1994 and
from 1992 to 1994, respectively, for computing the oceanic contributions to LOD changes, and, concerning the HAM variations,
the seasonal estimates of the hydrological contribution as derived by Chao and O'Connor [(1988) Geophys J 94: 263–270]. Using
vector representation, it is shown that the vectors achieve a close balance in the global axial angular momentum budget within
the estimated uncertainties of the momentum quantities on seasonal time scales.
Received: 6 April 2000 / Accepted: 13 December 2000 相似文献
18.
Tide gauge records of Hong Kong covering the past 45 years (1954.0–1999.0) are adopted to analyze the basic features of sea
level changes in the region. Data sets of atmospheric pressure, southern oscillation index and sea surface temperature during
the same time span are also used to determine the possible link between the sea level changes in Hong Kong and local and global
geophysical processes. Results indicate that the sea level of Hong Kong has a rising trend of 1.9 ± 0.4 mm per year, and that
there is an upward offset of about 15 cm in the pre-1957.0 tide gauge records. The effect of local atmospheric pressure variations
on the amplitude of the annual sea level change is about 30% of the amplitude that is calculated after the effect is corrected.
It is also found that the interannual variations in the sea level of Hong Kong are related to El Ni?o and La Ni?a events that
happen frequently in the tropical Pacific.
Received: 27 October 1999 / Accepted: 15 August 2000 相似文献
19.
The purpose of this paper is to demonstrate the effect of geophysical background model errors that affects temporal gravity
solutions provided by the Gravity Recovery And Climate Experiment (GRACE). Initial performance estimates by Dickey et al.
(1997) suggested a formal geoid RMS error better than 0.1 mm up to spherical harmonic degree 5. Now that the GRACE gravity
models and data are available, it is evident that these original expectations were too optimistic. Our hypothesis is that
this is partially explained by errors in geophysical background models that need to be applied in the GRACE data reduction,
and that this effect was not considered by Dickey et al. (1997). We discuss the results of a closed-loop simulation, where
satellite trajectory prediction software is used for the generation of GRACE range-rate data and GRACE orbit solutions with
the help of the Global Positioning System (GPS). During the recovery step in our closed-loop simulation, we show that simulated
nuisance signals (based on tide and air pressure model differences) map to a 0.7 mm geoid effect for periods longer than 3 months
and to less than 0.4 mm for periods shorter than 3 months. The long-period geoid hydrology signal is at a level of 4.5 mm,
while the short-period hydrology is at 0.25 mm. The long-period ocean bottom pressure (OBP) signal maps at 0.8 mm and for
short periods it is 0.4 mm. We conclude that short-period effects are difficult to observe by GRACE and that long-period effects,
like hydrology, are easier to recover than OBP variations. 相似文献
20.
水文气象因素引起的重力变化是影响地震重力变化成果解释的重要因素。以中国北疆地区为研究区域,借助全球陆地数据同化系统(global land data assimilation systems,GLDAS)全球水文模型数据、大气模型数据,计算2016-01—2017-12时段内水文气象因素对研究区域的重力影响。计算结果表明,陆地水影响的年变化为1.3 μGal,两期陆地水影响空间分布的差异低于1 μGal;大气影响的年变化为8 μGal,两期大气影响空间分布的差异达到6 μGal。利用2016-04、2016-08和2017-06三期流动重力测量数据,对比扣除水文气象因素前后的重力变化,可以看出,在中国北疆流动重力数据处理中,大尺度水文因素可以不予考虑,气象因素应予考虑。同时,为更好分析流动重力变化,建议流动重力测量过程中同时开展测点附近的土壤湿度、大气气压等观测。 相似文献