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51.
Simulation of the east asian summer monsoon using a variable resolution atmospheric GCM 总被引:6,自引:0,他引:6
The East Asia summer monsoon (EASM) is simulated with a variable resolution global atmospheric general circulation model (GCM) developed at the Laboratoire de Météorologie Dynamique, France. The version used has a local zoom centered on China. This study validates the model's capability in reproducing the fundamental features of the EASM. The monsoon behaviors over East Asia revealed by the ECMWF reanalysis data are also addressed systematically, providing as observational evidence. The mean state of the EASM is generally portrayed well in the model, including the large-scale monsoon airflows, the monsoonal meridional circulation, the cross-equatorial low-level jets, the monsoon trough in the South China Sea, the surface cold high in Australia, and the upper-level northeasterly return flow. While the performance of simulating large-scale monsoonal climate is encouraging, the model's main deficiency lies in the rainfall. The marked rainbelt observed along the Yangtze River Valley is missed in the simulation. This is due to the weakly reproduced monsoonal components in essence and is directly related to the weak western Pacific subtropical high, which leads to a fragile subtropical southwest monsoon on its western flank and results in a weaker convergence of the southwest monsoon flow with the midlatitude westerlies. The excessively westward extension of the high, together with the distorted Indian low, also makes the contribution of the tropical southwest monsoon to the moisture convergence over the Yangtze River Valley too weak in the model. The insufficient plateau heating and the resulting weak land-sea thermal contrast are responsible for the weakly reproduced monsoon. It is the deficiency of the model in handling the low-level cloud cover over the plateau rather than the horizontal resolution and the associated depiction of plateau topography that results in the insufficient plateau heating. Comparison with the simulation employing regular coarser mesh model reveals that the local zoom technique improves, in a general manner, the EASM simulation. 相似文献
52.
X射线衍射峰五基本要素的物理学意义与应用 总被引:6,自引:0,他引:6
本文根据Bragg衍射方程、Scherrer方程、衍射强度计算原理,研究讨论了X射线衍射5构成要素中的衍射峰位置、衍射峰宽度、衍射峰高度的物理学意义。根据实验研究证明了衍射峰不对称性的几何条件特征,并用地质事实验证了衍射形态变化与晶格应变和粒度大小的内在联系。从而阐明了单个衍射峰5基本构成要素的完整物理学意义,并以实例论证了5要素的实际应用价值。 相似文献
53.
Origin of a large breccia-vein system in the Sanerlin uranium deposit, southern China: a reinterpretation 总被引:1,自引:0,他引:1
The early Tertiary Sanerlin uranium deposit is located near the southwestern margin of the Chaling-Yongxing pull-apart basin defined by the Chaling-Yongxing and Chenxian-Linwu sinistral strike-slip faults in southern China. The uranium ores are hosted in 15 breccia-vein bodies, which are separately located in the cores of three secondary anticlines of the Upper Permian Dangchong Formation. Individual breccia-vein bodies are composed of fragments of silicified shale and sandstone from the Dangchong Formation, and quartz veinlets as cements. These fragments, together with quartz veins, form a mosaic texture. Hydrothermal pitchblende is the only commercial uranium mineral, mainly occurring as disseminated grains within quartz veins or coating fragments. Other metallic minerals include molybdenite, pyrite, chalcopyrite, galena, sphalerite, and red microcrystalline hematite. Fluid inclusions in quartz veins have homogenization temperatures ranging from 150 to 280 °C, and calculated salinity values between 5.6 and 13.4 wt% NaCl equivalent. Stable isotope analyses show that the mineralizing fluid was characterized by '18O values of -2.2 to +2.6 and 'DH2O values of -134 to -110. These analytical data demonstrate that hydrothermal fluids were mainly derived from formation waters (brines) of the Chaling-Yongxing basin. Fluid overpressuring was caused by an abnormal geothermal gradient and impermeable shales in the deposit area. The geometry, texture, and structure of the breccia-vein system, along with the fluid pressure estimates, suggest that hydraulic fracturing generated the mineralized breccia-vein system. Pitchblende and associated minerals were deposited when gaseous phases were released abruptly from the ore fluids due to the hydraulic fracturing. 相似文献
54.
55.
Tectonics and distribution of gold deposits in China – an overview 总被引:20,自引:0,他引:20
56.
Continental crust and lithospheric mantle interaction beneath North China: isotopic evidence from granulite xenoliths in Hannuoba, Sino-Korean craton 总被引:40,自引:0,他引:40
Mafic granulite and pyroxenite xenoliths from Cenozoic alkaline basalts at Hannuoba, Hebei Province, North China have been selected for a systematic geochemical and Sr–Nd–Pb isotopic study, which provides a unique opportunity to explore nature of the lower crust and the interaction between the continental crust and lithospheric mantle beneath an Archean craton. The major, compatible and incompatible elements and radiogenic isotopes of these xenoliths suggest great chemical heterogeneity of the lower crust beneath the Hannuoba region. Petrological and geochemical evidences indicate a clear cumulate origin, and most likely, they are related to basaltic underplating in different geological episodes. However, the Sr–Nd–Pb isotopic compositions of the xenoliths reveal a profound enriched source signature (EM I) with some influence of EM II, which implies that some portion of pre-existing, old metasomatized subcontinental lithospheric mantle could have played an important role in their genesis. It is suggested that the interaction between continental crust and subcontinental mantle as manifested by basaltic underplating would be closely related to regional tectonic episodes and geodynamic processes in the deep part of subcontinental lithospheric mantle. 相似文献
57.
中国西南及邻区上地幔P波三维速度结构/ 总被引:8,自引:0,他引:8
利用ISC报告以及中国和NEIC基本测震台网报告中的80974条P波初至到时资料(地震数为7053,台站数为165,且地震和台站都分布在研究区内),对中国西南及邻区(北纬10~36、东经70~110)的深至400km的上地幔三维速度结构进行了研究,分辨率达22.初步结果表明:①研究区速度的横向不均匀性,虽随深度增加而减弱,但至400km深度时仍很明显;②在北纬16和24的纵剖面上,可以看到与印度板块向东和欧亚板块相碰撞挤压相对应的速度结构,以及印度板块与欧亚板块速度结构的差异.在东经90的纵剖面上,与印度板块向北俯冲到欧亚板块(青藏高原)之下相对应的速度结构也比较明显;③在90km深度的横剖面上,由缅甸的密支那至越南的洞海的低速条带,可能与红河断裂带有关;④ 提出并使用了能够更为准确直观地描述分辨率好坏的图示方法. 相似文献
58.
59.
The experimental studies on electrical con-ductivities and P-wave velocities of anortho-site at high pressure and high temperature 总被引:1,自引:0,他引:1
Introduction The measurements of the compressional wave velocity and electrical conductivity of minerals and rocks are of fundamental importance to look into the earths interior, including composition, geotherm, generation and distribution of fluids and melts. Hydrous minerals formed by metamatu-siom are abundant within the earth. Previous studies have been carried out on the dehydration effect on the electrical conductivity and wave velocity of rocks such as serpentine, amphibole, most of whi… 相似文献
60.
Seismic structural control using semi-active tuned mass dampers 总被引:8,自引:1,他引:8
This paper focuses on how to determine the instantaneous damping of the semi-active tuned mass damper (SATMD) with continuously
variable damping. An off-and-towards-equilibrium (OTE) algorithm is employed to examine the control performance of the structure/SATMD
system by considering the damping as an assumptive control action. The damping modification of the SATMD is carried out according
to the proposed OTE algorithm, which is formulated based on analysis of the structural movement under external excitations,
and the measured responses of the structure at every time instant. As examples two numerical simulations of a five-storey
and a ten-storey shear structures with a SATMD on the roof are conducted. The effectiveness on vibration reduction of MDOF
systems subjected to seismic excitations is discussed. Analysis results show that the behavior of the structure with a SATMD
is significantly improved and the feasibility of applying the OTE algorithm to the structural control design of SATMD is also
verified. 相似文献