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Validating global hydrological models by ground and space gravimetry

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Chinese Science Bulletin 2009年第9期54卷 1534-1542页

作者： ZHOU JiangCun1,2,3. SUN HePing1,2 & XU JianQiao1,2 1 institute of geodesy and geophysics, Chinese academy of sciences,{3., china 2 key laboratory of dynamic geodesy, Chinese academy of sciences,{3., china 3.{13. University of Chinese academy of sciences, Beijing 100049, china institute of geodesy and geophysics Chinese Academy of Sciences Wuhan China key laboratory of dynamic {3. Chinese Academy of Sciences Wuhan China graduate University of Chinese academy of sciences Beijing China

The long-term continuous gravity observations obtained by the superconducting gravimeters (SG) at seven globally-distributed stations are comprehensively analyzed. After removing the signals related to the Earth's tides and variations in the Earth's rotation, the gravity residuals are used to describe the seasonal fluctuations in gravity field. Meanwhile, the gravity changes due to the air pressure loading are theoretically modeled from the measurements of the local air pressure, and those due to land water and nontidal ocean loading are also calculated according to the corresponding numerical models. The numerical results show that the gravity changes due to both the air pressure and land water loading are as large as 100×10-9 m s-2 in magnitude, and about 10×10-9 m s-2 for those due to the nontidal ocean loading in the coastal area. On the other hand, the monthly-averaged gravity variations over the area surrounding the stations are derived from the spherical harmonic coefficients of the GRACE-recovered gravity fields, by using Gaussian smoothing technique in which the radius is set to be 600 km. Com-pared the land water induced gravity variations, the SG observations after removal of tides, polar mo-tion effects, air pressure and nontidal ocean loading effects and the GRACE-derived gravity variations with each other, it is inferred that both the ground- and space-based gravity observations can effec-tively detect the seasonal gravity variations with a magnitude of 100×10-9 m s-2 induced by the land water loading. This implies that high precision gravimetry is an effective technique to validate the re-liabilities of the hydrological models.

关键词：重力测量水文模型模型验证和空间地面重力变化季节性波动空气压力

Sea level variations in the South china Sea inferred from satellite gravity,altimetry,and oceanographic data

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Science china Earth sciences 2012年第10期55卷 1696-1701页

作者： FENG Wei 1,2,ZHONG Min 1,3.& XU HouZe 1,3.1 State key laboratory of geodesy and Earth’s {3.s,institute of geodesy and geophysics,Chinese academy of sciences,wuhan 43.077,china 2 graduate University of Chinese academy of sciences,Beijing 100049,china 3.institute of geophysics,Huazhong University of Science and Technology,wuhan 43.074,china State key laboratory of geodesy and Earth’s {3.s Institute of Geodesy and Geophysics Chinese Academy of Sciences Wuhan China graduate University of Chinese academy of sciences Beijing China institute of geophysics Huazhong University of Science and Technology Wuhan China

Sea level variations(SLVs) can be divided into two major components:the steric SLV and the mass-induced *** two components of SLV in the South china Sea(SCS) are studied by using satellite altimetry,GRACE(Gravity Recovery and Climate Experiment) satellite gravity,and oceanographic data on annual and inter-annual *** the annual timescale,the geographic distribution of mass-induced SLV's amplitude jointly estimated from altimetry and the ECCO(Estimation of the Circulation and Climate of the Ocean) model agrees very well with that from *** observes obvious seasonal mass-induced SLV in the SCS with annual amplitude of 2.7±0.4 cm,which is consistent with the annual amplitude of 2.7±0.3.cm estimated from the steric-corrected *** the inter-annual timescales,the mean SLV in the SCS shows a large oscillation,which is mainly caused by the steric *** trend of mean SLV inferred from altimetry in the SCS is 5.5±0.7 mm/yr for the period of 1993.2009,which is significantly higher than the global sea level rise rate of 3.3.0.4 mm/yr in the same *** is no obvious trend signal in the mass-induced SLV detected from GRACE that indicates the water exchange between the SCS and its adjacent seas and land is in balance within the study period.

关键词： altimetry GRACE ECCO the South china Sea sea level variation

Spectral analysis of quasi-stationary sea surface topography from GRACE mission

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Science china Earth sciences 2005年第11期48卷 2040-2048页

作者： ZHANG Zizhan1,2 & LU Yang1,3.1. institute of geodesy and geophysics, Chinese academy of sciences,{3., china 2. graduate school of the Chinese academy of sciences, Beijing 10003., china 3. Unite Center for Astro-geodymics Research, Chinese academy of sciences, Shanghai 20003., china institute of geodesy and geophysics Chinese Academy of Sciences Wuhan China graduate school of the Chinese academy of {3. Beijing China Unite Center for Astro-geodymics Research Chinese Academy of Sciences Shanghai China

During the last two decades satellite altimetry has offered an abundance of meas-urements of the sea surface resulting in the improvement of global mean sea surface height (MSSH) and marine geoid determination. On the other hand, with the launching of new genera-tion gravity satellites, some high accuracy long-wavelength gravity models are available. These breakthroughs give us a great opportunity for new estimation of quasi-stationary sea surface topography (QSST). In this paper, the new gravity model GGM01C derived from GRACE mission is briefly presented, and a new global high precision and high-resolution QSST is determined based on the GGM01C model and the global MSSH. The spectral features of the QSST esti-mated by GGM01C and EGM96 gravity model to degree/order 200 are discussed by spectral analysis. As a result, the QSST is mainly composed of long waves, medium waves partially and short waves scarcely, its power spectral structures are different between the zonal direction and the meridional direction, there are great differences between the two models, which maybe ex-plain why the ocean currents derived from the two gravity models by Tapley show different pat-terns.

关键词： quasi-stationary sea surface topography, mean sea surface height, GGM01, fast Fourier transform, spectral analysis

The gravitational gradient tensor’s invariants and the related boundary conditions

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Science china Earth sciences 2010年第5期53卷 781-790页

作者： YU JinHai1,2,3.& ZHAO DongMing4 1 College of Earth Science, graduate University of Chinese academy of sciences, Beijing 100049,{3. 2 institute of geodesy and geophysics, Chinese academy of sciences, wuhan 43.077,{3. 3.State key laboratory of Astronautic dynamics, Xi’an 710043.{3. 4 Zhengzhou {13. of Surveying and Mapping, Zhengzhou 450052,{3. College of Earth Science Graduate University of Chinese Academy of Sciences Beijing China institute of geodesy and geophysics Chinese Academy of Sciences Wuhan China State key laboratory of Astronautic dynamics Xi’an China Zhengzhou institute of Surveying and Mapping Zhengzhou China

Here we report new approaches of recovering the Earth gravitational field from GOCE (Gravity field and steady-state Ocean Circulation Explorer) gradiometric data with the help of the gradient tensor’s invariants. Our results only depend on GOCE satellite’s position and gradiometry, in other words, they are completely independent of the satellite attitude. First, starting from the invariants, linearization models are established, which can be referred as the general boundary conditions on the satellite’s orbit. Then, the spherical approximation expressions for the models are derived, and the corresponding solving methods for them are discussed. Furthermore, considering effects of J2-term, the spherical approximation models are improved so that the accuracies of the boundary conditions can be theoretically raised to O ( J 2/2 T), which is approximately equivalent to O(T2). Finally, some arithmetic examples are constructed from EGM96 model based on the derived theories, and the computational results illustrate that the spherical models have accuracies of 10-7 and the order recovering the gravitational field can reach up to 200, and the models with regard to effect of J2-term have accuracies of 10-8 and the order can reach up to 280.

关键词： the Earth’s gravitational field gravitational gravidiometry tensor’s invariant

Variation properties of ionospheric eclipse factor and ionospheric influence factor

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Progress in Natural Science:Materials International 2005年第6期15卷 573-576页

作者： ZHAO Chunmei 1,2 *, YUAN Yunbin1, OU Jikun1 and CHEN Jinping3.1. institute of geodesy and geophysics, Chinese academy of sciences,{3., china 2. graduate school of Chinese academy of sciences, Beijing 10003., china 3. Department of Precision Instrument and Mechanology, Tsinghua University, Beijing 100084, china) institute of geodesy and geophysics Chinese Academy of Sciences Wuhan 430077 China graduate school Chinese Academy of Sciences Beijing 100039 China Department of Precision Instrument and Mechanology Tsinghua University Beijing 100084 China

The concepts and calculation methods of ionospheric eclipse factor (IEF) and ionospheric influence factor (IFF) are further illustrated. The temporal and spacial variation properties of IEF and IFF are studied, which shows that the properties are influenced by the geographic position and season. The possibility of improving the precision of using GPS data to determine ionospheric delay based on the above variation properties is also analysed.

关键词： GPS Ionospheric eclipse factor Ionospheric influence factor

Characteristics and geological significance of olivine xenocrysts in Cenozoic volcanic rocks from western Qinling

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Progress in Natural Science:Materials International 2006年第12期16卷 1300-1306页

作者： SU Benxun~ 1,2 **, ZHANG Hongfu~1, XIAO Yan~ 1,2 and ZHAO Xinmiao~ 1,2 (1. State key laboratory of Lithospheric Evolution, institute of Geology and {3., Chinese academy of sciences, Beijing 100029, china 2. graduate school of Chinese academy of sciences, Beijing 10003., china) State key laboratory of Lithospheric Evolution Institute of Geology and Geophysics Chinese Academy of Sciences Beijing 100029 China graduate school of Chinese academy of {3. Beijing 100039 China

Cenozoic volcanic rocks from the Haoti, Dangchang County of the western Qinling Mountains, contain a few clearly-zoned olivines. These olivines are relatively big in grain sizes and usually have cracks or broken features. Their cores have similar compositions （Mg#=90.4-91.0） to those for the peridotitic xenoliths entrained in host volcanic rocks and their rims are close to the compositions of olivine phenocrysts （Mg#=85.5-81.9）. The CaO contents in these zoned olivines are lower than 0.1%. These features demonstrate that the clearly-zoned olivines are xenocrysts and disaggregated from mantle peridotites. The zoned texture was the result of the interaction between the olivine and host magma. Available data show that the volcanic rocks would have been derived from the mantle source metasomatized by subducted hydrathermally-altered oceanic crust. The formation of these Cenozoic volcanic rocks was perhaps related to the rapid uplift of the Tibetan Plateau.

关键词： Western Qinling Dangchang Haoti Cenozoic volcanic rocks olivine xenocrysts zoned texture.

Interactions between hotspots and the Southwest Indian Ridge during the last 90 Ma:Implications on the formation of oceanic plateaus and intra-plate seamounts

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Science china Earth sciences 2011年第8期54卷 1177-1188页

作者： ZHANG Tao 1,2,3.4,LIN Jian 5 & GAO JinYao 3.4 1 institute of geodesy and geophysics,Chinese academy of sciences,{3. 43.077,china 2 graduate University of Chinese academy of sciences,Beijing 100049,china 3.The Second institute of Oceanography,State Oceanic Administrator,Hangzhou 3.0012,china 4 key {13. of Submarine Geosciences,State Oceanic Administrator,Hangzhou 3.0012,china 5 Department of Geology and geophysics,Woods Hole Oceanographic Institution,Woods Hole,MA 02543.USA institute of geodesy and geophysics Chinese Academy of Sciences Wuhan China graduate University of Chinese academy of sciences Beijing China The Second institute of Oceanography State Oceanic Administrator Hangzhou China key laboratory of Submarine Geosciences State Oceanic Administrator Hangzhou China

This study investigates the relationship between the hotspot-ridge interaction and the formation of oceanic plateaus and seamounts in the Southwest Indian *** first calculated the relative distance between the Southwest Indian Ridge (SWIR) and relevant hotspots on the basis of models of plate reconstruction,and then calculated the corresponding excess magmatic anomalies of the hotspots on the basis of residual bathymetry and Airy *** results reveal that the activities of the Marion hotspot can be divided into three main phases:interaction with the paleo-Rodrigues triple junction (73.6-68.5 Ma),interaction with the SWIR (68.5-42.7 Ma),and intra-plate volcanism (42.7-0 Ma).These three phases correspond to the formation of the eastern,central,and western parts of the Del Cano Rise,*** magnitude and apparent periodicity of the magmatic volume flux of the Marion hotspot appear to be dominated by the hotspot-ridge *** periodicity of the Marion hotspot is about 25 Ma,which is much longer than that of the Hawaii and Iceland hotspots (about 15 Ma).

关键词： Southwest Indian Ocean hotspot-ridge interaction magmatic volume flux oceanic plateaus seamounts

Determination of ocean tide loading displacements in Hong Kong using GPS technique

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Science china Earth sciences 2010年第7期53卷 993-1007页

作者： YUAN LinGuo1,3. DING XiaoLi1, SUN HePing2, ZHONG Ping1,3.& CHEN Wu1 1 Department of Land Surveying and Geo-Informatics, The Hong Kong Polytechnic University, Kowloon, Hong Kong, china 2 key laboratory of {3. geodesy, institute of geodesy and geophysics, Chinese academy of sciences, wuhan 43.077, china 3.Department of Surveying Engineering, school of Civil Engineering, Southwest Jiaotong University, Chengdu 61003., china Department of Land Surveying and Geo-Informatics The Hong Kong Polytechnic University Kowloon Hong Kong China Department of Surveying Engineering School of Civil Engineering Southwest Jiaotong University Chengdu China key laboratory of dynamic {3. Institute of Geodesy and Geophysics Chinese Academy of Sciences Wuhan China

Ocean tide loading (OTL) displacements of eight principal constituents at 12 sites in Hong Kong were determined using more than eight years of continuous GPS observations. Parameters of the OTL displacements were estimated using daily GPS solutions obtained with precise point positioning (PPP) technique. The results were compared with predictions from seven latest global ocean tide models. Gravity measurements of OTL in Hong Kong were also used to validate the GPS results. The study shows that the results from both the GPS and gravity measurements agree best with the GOT4.7 and NAO99b models, when the K1 and K2 constituents are excluded. The agreements between the GPS and the model estimates are generally at sub-millimeter level in both the horizontal and vertical directions, except for S2, K2 and K1 constituents that have relatively larger errors. After removing the systematic biases between the GPS and the model estimates, the misfits of M2, S2, N2, O1, P1 and Q1 at all sites are within 0.5 and 1.0 mm in the horizontal and the vertical directions, respectively, whereas K1 and K2 show relatively larger misfits of up to 2.3.mm. Both the GPS and the gravity S2 estimates have large biases with unknown reasons when compared with the modeled values, which needs to be further investigated. The study demonstrates that GPS is capable of estimating the OTL displacements with the same accuracy as the model predictions, especially for coastal areas.

关键词： GPS ocean tide loading ocean tide model site displacement

A tentative study for the prediction of the CME related geomagnetic storm intensity and its transit time

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Science china(Technological sciences) 2005年第6期48卷 648-668页

作者： ZHAO Xinhua1,2 & FENG Xueshang1,3.1. SIGMA Weather Group, key laboratory of Space Weather, Center for Space Science and Applied Re-search, Chinese academy of {3., Beijing 100080, china 2. graduate school of the Chinese academy of {3., Beijing 10003., china 3. school of geophysics and Geoinformation Systems, china University of Geo{3., Beijing 100083. china SIGMA Weather Group Key Laboratory of Space Weather Center for Space Science and Applied Research Chinese Academy of Sciences Beijing China graduate school of the Chinese academy of {3. Beijing China school of geophysics and Geoinformation Systems China University of Geosciences Beijing China

Using 80 CME-ICME events during 1997.1―2002.9, based on the eruptive source locations of CMEs and solar magnetic field observation at the photosphere, a current sheet magnetic coordinate (CMC) system is established in order to study the propagation of CME and its geoeffectiveness. In context of this coordinate system, the effect of the eruptive source location and the form of heliospheric current sheet (HCS) at the eruptive time of CME on the geomagnetic storm intensity caused by CME and the CME’s transit time at the Earth is investigated in detail. Our preliminary conclusions are: 1) The geomagnetic disturbances caused by CMEs tend to have the so-called “same side-opposite side effect”, i.e. CMEs erupt from the same side of the HCS as the earth would be more likely to arrive at the earth and the geomagnetic disturbances associated with them tend to be of larger magnitude, while CMEs erupting from the opposite side would arrive at the earth with less probability and the corresponding geomagnetic disturbance magnitudes would be relatively weaker. 2) The angular separation between the earth and the HCS affect the corresponding disturbance intensity. That is, when our earth is located near the HCS, adverse space weather events occur most probably. 3. The erupting location of the CME and its nearby form of HCS will also affect its arrival time at the earth. According to these conclusions, in this context of CMC coordinate we arrive at new prediction method for estimating the geomagnetic storm intensity (Dstmin) caused by CMEs and their transit times. The application of the empirical model for 80 CME-ICME events shows that the relative error of Dst is within 3.% for 59% events with Dstmin≤?50 nT, while the averaged absolute error of transit time is lower than 10 h for all events.

关键词： coronal mass ejections, current sheet magnetic coordinate system, geomagnetic storm intensity, transit time, prediction method.