河西地区重力动态变化的二维离散小波多尺度分解   总被引：7，自引：5，他引：2  

朱桂芝  祝意青  唐文  程宏宾 《大地测量与地球动力学》2004,24(1):46-49

采用二维离散小波的多尺度分解技术，对1994～1995年和2002～2003年的河西地区重力动态变化进行分解，提取该地区不同层次的重力动态变化异常，结果反映了不同深度在一定尺度意义上的介质密度的动态变化分布。  相似文献   

全球纬向平均的海气耦合一维模式分析     

唐佑民 《成都信息工程学院学报》1991,(1)

本文从能量平衡角度,考虑海气相互作用和纬向间的差异,设计了一个纬向平均的海气耦合一维模式,进行了模式平衡态求解、敏感性试验以及随机分析。并对模式部分计算结果进行了与实测资料的比较,验证了模式的合理性和可信性。  相似文献   

A mass‐balance approach to estimate in‐stream processes in a large river     

Samuel Teissier  Sabine Sauvage  Philippe Vervier  Frédéric Garabétian  José‐Miguel Sánchez‐Pérez 《水文研究》2008,22(3):420-428

A mass‐balance approach was used to estimate in‐stream processes related to inorganic nitrogen species (NH₄⁺, NO₂^? and NO₃^?) in a large river characterized by highly variable hydrological conditions, the Garonne River (south‐west France). Studies were conducted in two consecutive reaches of 30 km located downstream of the Toulouse agglomeration (population 760 000, seventh order), impacted by modification of discharge regime and high nitrogen concentrations. The mass‐balance was calculated by two methods: the first is based on a variable residence time (VRT) simulated by a one‐dimensional (1‐D) hydraulic model; the second is a based on a calculation using constant residence time (CRT) evaluated according to hydrographic peaks. In the context of the study, removal of dissolved inorganic nitrogen (DIN) for a reach of 30 km is underestimated by 11% with the CRT method. In sub‐reaches, the discrepancy between the two methods led to a 50% overestimation of DIN removal in the upper reach (13 km) and a 43% underestimation in the lower reach (17 km) using the CRT method. The study highlights the importance of residence time determination when using modelling approaches in the assessment of whole stream processes in short‐duration mass‐balance for a large river under variable hydrological conditions. Copyright © 2007 John Wiley & Sons, Ltd.  相似文献   

Advancing process‐based watershed hydrological research using near‐surface geophysics: a vision for,and review of,electrical and magnetic geophysical methods     

D. A. Robinson  A. Binley  N. Crook  F. D. Day‐Lewis  T. P. A. Ferré  V. J. S. Grauch  R. Knight  M. Knoll  V. Lakshmi  R. Miller  J. Nyquist  L. Pellerin  K. Singha  L. Slater 《水文研究》2008,22(18):3604-3635

We want to develop a dialogue between geophysicists and hydrologists interested in synergistically advancing process based watershed research. We identify recent advances in geophysical instrumentation, and provide a vision for the use of electrical and magnetic geophysical instrumentation in watershed scale hydrology. The focus of the paper is to identify instrumentation that could significantly advance this vision for geophysics and hydrology during the next 3–5 years. We acknowledge that this is one of a number of possible ways forward and seek only to offer a relatively narrow and achievable vision. The vision focuses on the measurement of geological structure and identification of flow paths using electrical and magnetic methods. The paper identifies instruments, provides examples of their use, and describes how synergy between measurement and modelling could be achieved. Of specific interest are the airborne systems that can cover large areas and are appropriate for watershed studies. Although airborne geophysics has been around for some time, only in the last few years have systems designed exclusively for hydrological applications begun to emerge. These systems, such as airborne electromagnetic (EM) and transient electromagnetic (TEM), could revolutionize hydrogeological interpretations. Our vision centers on developing nested and cross scale electrical and magnetic measurements that can be used to construct a three‐dimensional (3D) electrical or magnetic model of the subsurface in watersheds. The methodological framework assumes a ‘top down’ approach using airborne methods to identify the large scale, dominant architecture of the subsurface. We recognize that the integration of geophysical measurement methods, and data, into watershed process characterization and modelling can only be achieved through dialogue. Especially, through the development of partnerships between geophysicists and hydrologists, partnerships that explore how the application of geophysics can answer critical hydrological science questions, and conversely provide an understanding of the limitations of geophysical measurements and interpretation. Copyright © 2008 John Wiley & Sons, Ltd.  相似文献   

Jurassic‐to‐present thermal history of the central High Atlas (Morocco) assessed by low‐temperature thermochronology     

Luis Barbero  Antonio Teixell  María‐Luisa Arboleya  Pedro del Río  Peter W. Reiners  Blaid Bougadir 《地学学报》2007,19(1):58-64

Apatite fission track (AFT) and (U–Th)/He data from the High Atlas have been obtained for the first time to constrain the tectono‐thermal evolution of the central part of the chain. Results from Palaeozoic basement massifs indicate long residence at low temperatures, consistently with their original location out of the deepest Mesozoic rift troughs and indicating minor exhumation. The best rocks for extracting the Alpine history of the Atlas Mountains are Jurassic intrusives, which yield AFT ages centred on c. 80 Ma; thermal models based on AFT data and constrained by (U–Th)/He suggest that these ages are included in a slow cooling trend from intrusion age to c. 50 Ma ago that we attribute to post‐rift thermal relaxation. This is followed by a stability period of c. 30 Ma and then by a final exhumational cooling until present exposure. Eocene intrusives yield AFT ages similar to those of Rb–Sr and K–Ar suggesting rapid emplacement in the uppermost crust.  相似文献   

Uniform Permian 40Ar/39Ar detrital mica ages in the eastern Qaidam Basin (NW China): where is the source?     

Andrea B. Rieser  Yongjiang Liu  Johann Genser  Franz Neubauer  Robert Handler  Xiao‐Hong Ge 《地学学报》2006,18(1):79-87

New single‐grain ⁴⁰Ar/³⁹Ar detrital white‐mica ages from the Lulehe section at the eastern Qaidam Basin yield uniform Permian ages between 250 ± 3 and 279 ± 3 Ma throughout the whole Cenozoic sequence. This is inconsistent with the present hinterland, which is composed of early Palaeozoic metamorphic units with subordinate early Palaeozoic and few Permian granites. The new data indicate that Permian tectonic units are likely more widespread at the north‐eastern margin of the Tibetan plateau as known at present, particularly within the Qilian Mountains. The preferred explanation is that the Qaidam block represents a rigid indenter, which indented during late Tertiary times into early Palaeozoic orogenic units. This is consistent with recent findings of a NW‐trending sinistral Permian ductile shear zone and a dextral, NW‐trending Tertiary fault system close to the north‐eastern margin of the Qaidam Basin.  相似文献   

Scattering of elastic wave by a partially sealed cylindrical shell embedded in poroelastic medium     

Liu Gan‐Bin  Xie Kang‐He  Yao Hai‐lin 《国际地质力学数值与分析法杂志》2005,29(11):1109-1126

Scattering of an elastic wave by a cylindrical shell embedded in poroelastic medium is investigated theoretically with the assumption that the shell material is also a porous elastic medium. The porous medium is modellized via Biot's theory and the scattering by cylindrical shell is expressed by the definition of scattering matrix. The normal mode expansion technique is employed for analysing the scattering field, and the asymptotic solutions of displacements, stresses and pore pressure are derived. Two limiting cases‐scattering by a poroelastic cylinder in Biot medium and a elastic cylindrical shell in elastic medium are obtained from the general solutions. The dispersion curves of displacement amplitude at the interface of shell and medium is compared with the case of elastic shell. The scattering amplitude associated with the fast, slow and transverse waves are identified by numerical simulation. Furthermore, the influence of the poroelastic property of shell material on scattering amplitude is analysed. Copyright © 2005 John Wiley & Sons, Ltd.  相似文献   

Analysis of geomorphologic and hydrological characteristics in watershed saturated areas using topographic‐index threshold and geomorphology‐based runoff model     

Chin‐Hsin Chang  Kwan Tun Lee 《水文研究》2008,22(6):802-812

The objective of this paper is to investigate the variation of geomorphology and runoff characteristics in saturated areas under different partial contributing area (PCA) conditions. Geomorphologic information and hydrologic records from two mid‐size watersheds in northern Taiwan were selected for analysis. The PCA ratio in the watershed during a storm was assumed equal to the ratio of the surface‐flow volume to the direct runoff volume from measured hydrologic data. The extents of PCA regions were then determined by using a topographic‐index threshold. Consequently, the geomorphologic factors in saturated and unsaturated areas could be calculated using a digital elevation model, and these factors could then be linked to a geomorphology‐based IUH model for runoff simulation, which can consider both the surface‐ and subsurface‐flow processes in saturated and unsaturated areas, respectively. The results show that geomorphologic characteristics in the saturated areas vary significantly with different PCA ratios especially for higher order streams. A large PCA ratio results in a sharp hydrograph because the quick surface flow dominates the runoff process, whereas the hydrologic response in a low PCA case is dominated by the delayed subsurface flow. Copyright © 2007 John Wiley & Sons, Ltd.  相似文献   

A neural network atmospheric model for hybrid coupled modelling     

Y. Tang  W. W. Hsieh  B. Tang  K. Haines 《Climate Dynamics》2001,17(5-6):445-455

 The possibility of using a nonlinear empirical atmospheric model for hybrid coupled atmosphere-ocean modelling has been examined by using a neural network (NN) model for predicting the contemporaneous wind stress field from the upper ocean state. Upper ocean heat content (HC) from a 6-layer ocean model was a better predictor of the wind stress than the (observed or modelled) sea surface temperature (SST). Our results showed that the NN model generally had slightly better skills in predicting the contemporaneous wind stress than the linear regression (LR) model in the off-equatorial tropical Pacific and in the eastern equatorial Pacific. When the wind stresses from the NN and LR models were used to drive the ocean model, slightly better SST skills were found in the off-equatorial tropical Pacific and in the eastern equatorial Pacific when the NN winds were used instead of the LR winds. Better skills for the model HC were found in the western and central equatorial Pacific when the NN winds were used instead of the LR winds. Why NN failed to show more significant improvement over LR in the equatorial Pacific for the wind stress and SST is probably because the relationship between the surface ocean and the atmosphere in the equatorial Pacific over the seasonal time scale is almost linear. Received: 2 March 1999 / Accepted: 13 July 2000  相似文献   

Hybrid coupled models of the tropical Pacific – II ENSO prediction     

Y. Tang  W. Hsieh 《Climate Dynamics》2002,19(3-4):343-353

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