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991.
Experimental outputs of 11 Atmospheric Model Intercomparison Project (AMIP) models from phase 5 of the Coupled Model Intercomparison Project (CMIP5) are analyzed to assess the atmospheric circulation anomaly over Northern Hemisphere induced by the anomalous rainfall over tropical Pacific and Indian Ocean during boreal winter.The analysis shows that the main features of the interannual variation of tropical rainfall anomalies,especially over the Central Pacific (CP) (5°S-5°N,175°E-135°W) and Indo-western Pacific (IWP) (20°S-20°N,110°-150°E) are well captured in all the CMIP5/AMIP models.For the IWP and western Indian Ocean (WIO) (10°S-10°N,45°-75°E),the anomalous rainfall is weaker in the 11 CMIP5/AMIP models than in the observation.During El Ni(n)o/La Ni(n)a mature phases in boreal winter,consistent with observations,there are geopotential height anomalies known as the Pacific North American (PNA) pattern and Indo-western Pacific and East Asia (IWPEA) pattern in the upper troposphere,and the northwestern Pacific anticyclone (cyclone) (NWPA) in the lower troposphere in the models.Comparison between the models and observations shows that the ability to simulate the PNA and NWPA pattern depends on the ability to simulate the anomalous rainfall over the CP,while the ability to simulate the IWPEA pattern is related to the ability to simulate the rainfall anomaly in the IWP and WIO,as the SST anomaly is same in AMIP experiments.It is found that the tropical rainfall anomaly is important in modeling the impact of the tropical Indo-Pacific Ocean on the extratropical atmospheric circulation anomaly. 相似文献
992.
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993.
994.
Ahmed I. Rushdi Peter U. Clark Alan C. Mix Vasile Ersek Bernd R. T. Simoneit Hai Cheng R. Lawrence Edwards 《Environmental Earth Sciences》2011,62(6):1245-1261
We analyzed speleothem calcite from the Oregon Caves National Monument, southwestern Oregon, to determine the preservation,
distribution, concentrations and sources of aliphatic lipid compounds preserved in the calcite. Maximum speleothem growth
rate occurs during interglaciations and minimum during glacial intervals. Concentrations of the total lipid compounds range
from 0.5 to 12.9 μg g−1. They increase at times of low speleothem growth rate, suggesting dilution, whereas the apparent accumulation rate of lipid
compounds tends to be highest during times of fastest speleothem growth rate. Such increased accumulation generally corresponds
to times of warm (interglacial) climate, suggesting either a greater source of organic materials during interglacial times
and/or greater efficiency of compound capture during more rapid calcite growth. Aliphatic lipid compounds include homologous
n-alkanoic acids, n-alkanols and methyl n-alkanoates and sterols with concentrations ranging from 0.3 to 7.8 μg g−1, 0.4 to 1.1 μg g−1, 0.5 to 9.6 μg g−1 and 0.1 to 2.7 μg g−1, respectively. Minor amounts of branched methyl n-alkanoates and dimethyl n-alkanedioates are also present. The high concentrations of methyl n-alkanoates are the result of esterification reactions of free fatty acids in alkaline solutions with high pH values associated
with the dripping cave waters. The distribution patterns and geochemical parameters and indices indicate that the major sources
of the aliphatic lipids involved leaching from higher plants and microbial residues derived from the soil zone above the cave
system. The estimated percentage of microbial inputs ranged from 42 to 90% of the total lipids and also showed an increase
in accumulation during warm climates. These well-preserved lipid compounds in speleothem calcite could be used as biomarkers
for paleoenvironmental study. 相似文献
995.
996.
997.
通过实地地质调查和取样测试,对二里河铅锌矿床进行标型矿物微量元素、围岩稀土元素地球化学特征、流体包裹体特征分析。结果表明:二里河铅锌矿床具有海底热水喷流沉积矿床一般地质特征,多期(华力西期+印支期)构造运动和幅度较大的裂陷发育史为大量矿质的喷流和聚集提供了十分有利的导矿和容矿构造条件。标型矿物微量元素地球化学特征显示:闪锌矿明显富集Cd((6 493.74~7 225.68)×10-6),贫Sb、As,黄铁矿w(S)与w(Se)比值为23 443.48~250 284.36,w(Co)与w(Ni)比值为3.47~104.10,指示矿床具热水沉积特征,而黄铁矿w(Fe)/(w(S)+w(As))为0.87~1.52,表明该矿为浅部成因矿床;流体包裹体特征、围岩和闪锌矿稀土元素显著亏损Eu、Ce,指示二里河铅锌矿床可能具有喷流沉积型矿床远源矿化特征;log(δCe)为-0.04~0.04,表明二里河铅锌矿床围岩在还原环境下成岩;石英流体包裹体均一温度及闪锌矿成分指示的温度范围(215℃~333℃)特征表明该矿床为中温矿床。综上所述,二里河铅锌矿床可能为相对远离喷流口的喷流沉积型浅层中温层状矿床。 相似文献
998.
An analytical solution of cavity expansion in two different concentric regions of soil is developed and investigated in this paper. The cavity is embedded within a soil with finite radial dimension and surrounded by a second soil, which extends to infinity. Large‐strain quasi‐static expansion of both spherical and cylindrical cavities in elastic‐plastic soils is considered. A non‐associated Mohr–Coulomb yield criterion is used for both soils. Closed‐form solutions are derived, which provide the stress and strain fields during the expansion of the cavity from an initial to a final radius. The analytical solution is validated against finite element simulations, and the effect of varying geometric and material parameters is studied. The influence of the two different soils during cavity expansion is discussed by using pressure–expansion curves and by studying the development of plastic regions within the soils. The analytical method may be applied to various geotechnical problems, which involve aspects of soil layering, such as cone penetration test interpretation, ground‐freezing around shafts, tunnelling, and mining. © 2014 The Authors. International Journal for Numerical and Analytical Methods in Geomechanics published by John Wiley & Sons Ltd. 相似文献
999.
随着国内市场对天然气需求量的迅速增长,如何成功开发宁武盆地储量丰富的煤层气资源已成为目前非常规气藏开发的一个重要课题。结合宁武盆地地应力状态、地层孔隙压力、地层强度参数、井斜角和方位角等参数,科学确定适合煤层气井钻进的钻井液密度窗口,成为宁武盆地煤层气项目能够高效、安全实现产业化发展的关键因素之一。通过ANSYS软件对宁武盆地9号煤层建立有限元模型,分别分析了不同地应力方向时不同井斜角钻井液密度对井眼扩大率的影响规律,针对不同方位和井斜得出了适用的钻井液密度窗口,对于下一步宁武盆地煤层气井产业化开发中有效控制煤层坍塌,降低复杂情况,提高钻井效率及提高煤层气开发综合效益提供了技术支撑。 相似文献
1000.
西藏羌塘盆地以发育中生代海相地层为特征,成为近年来油气勘探的重要区块。对于整个盆地的中生代海相沉积是否跨入早白垩世过去仍存在一些争议。本次在光明湖一带的白龙冰河组上部采集到大量早白垩世化石,证实了该组沉积晚期已跨入早白垩世,为区域上与该组同时异相的其它中生代地层沉积时代的进一步厘定提供了新的化石依据。对整个羌塘盆地晚侏罗世—早白垩世沉积古地理的研究,以及羌塘盆地早白垩世海相地层的圈定和油气地质条件的探讨具有重要意义。 相似文献