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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 {2., chinese academy of sciences, wuhan 430077, china 2.Key Laboratory of dynamic geodesy, chinese academy of sciences, wuhan 430077, china 3 Graduate University of chinese academy of sciences, Beijing 100049, china institute of Geodesy and geophysics Chinese Academy of Sciences Wuhan China Key Laboratory of dynamic geodesy 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

Experimental earth tidal models in considering nearly diurnal free wobble of the Earth's liquid core

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Science Bulletin 2003年第9期48卷 935-940页

作者： sun Heping, XU Jianqiao & B. Ducarme Key Laboratory of dynamic Geodesy, {2. of Geodesy and geophysics, chinese academy of sciences, wuhan 430077, china Observatoire Royal de Belgique, Av. Circulaire 3, B-1180, Brussels, Belgium Correspondence should be addressed to sun Heping (e-mail: heping@ ***) Key Laboratory of dynamic Geodesy Institute of Geodesy and Geophysics Chinese Academy of Sciences Wuhan 430077 China Observatoire Royal de Belgique Av. Circulaire 3 B-1180 Brussels Belgium

Based on the 2. series of the high precision and high minute sampling tidal gravity observations at 2. stations in Global Geodynamics Project (GGP) network, the resonant parameters of the Earth's nearly diurnal free wobble (including the eigenperiods, resonant strengths and quality factots) are precisely determined. The discrepancy of the eigenperiod between observed and theoretical values is studied, the important conclusion that the real dynamic ellipticity of the liquid core is about 5% larger than the one under the static equilibrium assumption is approved by using our gravity technique. The experimental Earth's tidal gravity models with considering the nearly diurnal free wobble of the Earth's liquid core are constructed in this study. The numerical results show that the difference among three experimental models is less than 0.1%, and the largest discrepancy compared to those widely used nowdays given by Dehant (1999) and Mathews (2.01) is only about 0.4%. It can provide with the most recent real

关键词： Earth’s nearly diurnal free wobble global observations of superconducting gravimeters dynamic ellipticity of liquid core experimental earth tidal models.

Quasirational dynamic system

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chinese Science Bulletin 2000年第14期45卷 1277-1279页

作者： sun Daochun & YANG Lo1. Department of Mathematics, South china Normal University, Guangzhou 510631, china 2. institute of Mathematics, academy of Mathematics and System sciences, chinese academy of sciences, Beijing 100080, china Department of Mathematics South China Normal University Guangzhou China institute of Mathematics Academy of Mathematics and System Sciences Chinese Academy of Sciences Beijing China

Using the iterations of quasirational mappings, the theorems on dynamic system are generalized to the quasirational dynamic system. Some different results are also obtained.

关键词： quasirational mapping dynamic system covering surface.

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 {2. Geodesy, institute of Geodesy and geophysics, chinese academy of sciences, wuhan 430077, china 3 Department of Surveying Engineering, School of Civil Engineering, Southwest Jiaotong University, Chengdu 610031, 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 Geodesy 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

Influence of the earth rotation on the interfacial wave solutions and wave-induced tangential stress in a two-layer fluid system

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Acta Oceanologica Sinica 2009年第2期28卷 115-120页

作者： SONG Jinbao LIU Yongjun institute of Oceanology Chinese Academy of Sciences Qingdao 266071 China Key Laboratory of Ocean Circulation and Waves （KLOCAW） Chinese Academy of Sciences Qingdao 266071 China Graduate University of chinese academy of sciences Beijing 100039 China

Interfacial waves and wave-induced tangential stress are studied for geostrophic small amplitude waves of two-layer fluid with a top free surface and a fiat bottom. The solutions were deduced from the general form of linear fluid dynamic equations of two-layer fluid under the f-plane approximation, and wave-induced tangential stress were estimated based on the solutions obtained. As expected, the solutions derived from the present work include as special cases those obtained by sun et al. （2.04. Science in{2., Ser. D, 47（12.： 1147-1154） for geostrophic small amplitude surface wave solutions and wave-induced tangential stress if the density of the upper layer is much smaller than that of the lower layer. The results show that the interface and the surface will oscillate synchronously, and the influence of the earth＇s rotation both on the surface wave solutions and the interfacial wave solutions should be considered.

关键词： two-layer fluid interfacial waves wave-induced tangential stress earth rotation

The retrieval of two-dimensional distribution of the earth's surface aerodynamic roughness using SAR image and TM thermal infrared image

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Science china Earth sciences 2004年第12期47卷 1134-1146页

作者： ZHANG Renhua 1 ,WANG Jinfeng 1 ,ZHU Caiying 1,2.,sun Xiaomin 1 & ZHU Zhilin 1 1.institute of Geographical {2. and Natural Resources,chinese academy of {2.,Beijing 100101,china 2.institute of Surveying and Mapping,Information Engineering University of the chinese People’s Liberation Army,Zhengzhou 450052.china chinese academy of {2. Institute of Geographical Sciences and Natural Resources Beijing China Information Engineering University of the chinese People’s Liberation Army Institute of Surveying and Mapping Zhengzhou China

After having analyzed the requirement on the aerodynamic earth’s surface rough- ness in two-dimensional distribution in the research field of interaction between land surface and atmosphere, this paper presents a new way to calculate the aerodynamic roughness using the earth’s surface geometric roughness retrieved from SAR (Synthetic Aperture Radar) and TM thermal infrared image data. On the one hand, the SPM (Small Perturbation Model) was used as a theoretical SAR backscattering model to describe the relationship between the SAR back- scattering coefficient and the earth’s surface geometric roughness and its dielectric constant re- trieved from the physical model between the soil thermal inertia and the soil surface moisture with the simultaneous TM thermal infrared image data and the ground microclimate data. On the basis of the SAR image matching with the TM image, the non-volume scattering surface geo- metric information was obtained from the SPM model at the TM image pixel scale, and the ground pixel surface’s equivalent geometric roughness—height standard RMS (Root Mean Square) was achieved from the geometric information by the transformation of the typical to- pographic factors. The vegetation (wheat, tree) height retrieved from spectrum model was also transferred into its equivalent geometric roughness. A completely two-dimensional distribution map of the equivalent geometric roughness over the experimental area was produced by the data mosaic technique. On the other hand, according to the atmospheric eddy currents theory, the aerodynamic surface roughness was iterated out with the atmosphere stability correction method using the wind and the temperature profiles data measured at several typical fields such as bare soil field and vegetation field. After having analyzed the effect of surface equivalent geo- metric roughness together with dynamic and thermodynamic factors on the aerodynamic surface roughness within the working area, this paper first establishe

关键词： surface geometric roughness, aerodynamic surface roughness, SAR backscattering model, moisture retrieval model, roughness transformation model.

General regularity of dynamic responses of slopes under dynamic input

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Science china(Technological sciences) 2003年第Z1期46卷 120-132页

作者： QI Shengwen, WU Faquan & sun Jinzhong institute of Geology and {2., chinese academy of sciences, Beijing 10002., china College of Engineering Technique, china University of Geosciences, Beijing 100083, china chinese Acad Sci Inst Geol & Geophys Beijing 100029 Peoples R China china Univ Geosci Coll Engn Techn Beijing 100083 Peoples R China

Through lots of numerical simulations with FLAC3D, dynamic responses of slopes are comprehensively studied in this paper and the general regularities of the isoline of the coefficient of the displacement, velocity and acceleration of the slope section are reached. Given a certain material slope, if the height of the slope is less than a certain value, the displacement, velocity and acceleration linearly enlarge with elevation in the vertical direction; if the height of the slope surpasses the certain value, the displacement,velocity and acceleration do not linearly enlarge with elevation any more, on the other hand, they fluctuate with a certain rhythm. At the same time, the rhythm appears in the horizontal direction, and the displacement, velocity and acceleration of the slope surface enlarge near the slope surface. The distribution form of the isoline of the coefficient of displacement, velocity and acceleration in the section of the slope is remarkably affected by the slope angle. In the certain area near the slope surface, the isoline of displacement,velocity and acceleration is parallel to the surface of the slope; in the mean time the strike direction of the extremum area is parallel to the surface of the slope, too. The charts of the slope dynamic responses can be depicted with two indexes, one is the strike direction of the isoline, and the other is the number of the rhythm extremum area of the direction parallel to the surface of the slope.

关键词： slope, dynamic response, regularity, rhythm.

Ab-initio molecular dynamics simulation on nano-system under external pressure

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Science china Mathematics 2004年第Z1期47卷 92-100页

作者： Jl Min, sun Deyan & GONG XingaoSurface Physics Laboratory and Department of Physics, Fudan University, Shanghai 2.0433, china {2. of Solid State Physics, chinese academy of sciences, Hefei 2.0031, china Interdisciplary Center for Theoretical studies, chinese academy of sciences, Beijing 100080, china Surface Physics Laboratory and Department of Physics Fudan University Shanghai China institute of Solid State Physics Chinese Academy of Sciences Hefei China Interdisciplary Center for Theoretical studies Chinese Academy of Sciences Beijing China

A new constant-pressure molecular dynamics (MD) method is developed to simulate the dynamic behavior and structure transition of finite system under external pressure. In this method, no artificial parameter is introduced and the computation overheads are very small. As an application, a hard-soft transition of single wall carbon nanotube (SWCNT) under external pressure is found, which is in agreement with the experiments.

关键词： phase transition, simulation, nano-particles

Analysis on the dynamical Process of Donghekou Rockslide-Debris Flow Triggered by 5.12.Wenchuan Earthquake

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Journal of Mountain Science 2011年第2期8卷 140-148页

作者： sun Ping ZHANG Yongshuang SHI Jusong CHEN Liwei Key Laboratory of Neotectonic Movement & Geohazard Ministry of Land and Resources Beijing China institute of Geomechanics Chinese Academy of Geological Sciences Beijing China china Nuclear Power Engineering Corporation Ltd. Beijing China

Among the geo-hazards caused by the great Wenchuan Earthquake, the rapid and long runout rockslide-debris flow is of primary concern due to the large volume of displaced material and the resultant catastrophic impacts to the landscape and socioeconomic structure. In order to analyze the dynamical process of this kind of geo-hazard, the Donghekou rockslide-debris flow is given as an example in this paper. This event, which killed 780 people, initiated at an elevation of 1300 m with a total long run-out distance of more than 2.00 m. The slide mass is mainly composed of dolomite limestone and siliceous limestone of Sinian system, together with carbon slate and phyllite of Cambrian. During the processes from slide initiation to the final cessation of slide movement, five dynamic stages took place, here identified as the initiation stage, the acceleration of movement stage, the air-blast effect stage, the impact and redirection stage and the long runout slidematerial accumulation stage. Field investigations indicate that due to the effects of the earthquake, the dynamics of the Donghekou rockslide-debris flow are apparently controlled by geologic and tectonic conditions, the local geomorphological aspects of the terrain, and the microstructural and macroscopic mechanical properties of rocks which compose the slide mass. These three main factors which dictate the Donghekou rockslide-debris flow dynamics are discussed in detail in this paper, and significant results of field investigations and tests of materials are presented. The above dynamical processes are analyzed in this paper, and some useful conclusions have been gained.

关键词： dynamical process Donghekou Rockslide-debris flow Wenchuan earthquake