共查询到19条相似文献，搜索用时 156 毫秒
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中国表土花粉与建群植物地理分布的气候指示性对比 总被引：5，自引：0，他引：5
利用中国建群植物数字化的地理分布数据与1860个中国表土样品花粉数据和气候插值,定量分析了中国主要花粉含量与植物种类的地理分布和气候指示性．研究结果显示,绝大多数表土花粉含量的气候指示性与建群植物地理分布的气候区间是吻合的,表土花粉与建群植物的气候阈值的重合取决于花粉与气候的正态分布关系．此外,部分花粉种类指示的气候相对于植物存在一定的偏移,如杜鹃花科、菊科、禾本科和藜科等,这与花粉的分类鉴定水平较低和自然植被的人为干扰有关．本研究在较大空间尺度范围内将表土花粉与建群植物的气候指示性进行对比,为全球生态学、第四纪环境和古气候学研究提供了重要的数据和参照． 相似文献
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δEuN-∑REEs图解定量区分长江和黄河沉积物 总被引：4，自引：0，他引：4
对取自长江下游河道和黄河的沉积物样品进行了稀土元素分析,并搜集了文献资料中长江和黄河沉积物样品的稀土元素数据,发现在δEuN-∑REEs关系图中长江和黄河沉积物之间有一条明显的分界线,回归分析表明该分界线是一个3次多项式方程,在该界线的上方是长江沉积物,下方是黄河沉积物．为了考察该分界线的合理性及其应用价值,在长江口和黄河口分别取样进行稀土元素分析,并搜集了来源于长江255孔和源于黄河的YA01孔沉积物的稀土元素数据．在δEuN—∑REEs关系图中,长江口和255孔沉积物绝大部分分布在长江沉积物的区域,而黄河口和YA01孔沉积物绝大部分分布在黄河沉积物的区域．因此,通过δEuN-∑REEs关系图和回归曲线方程,可以直观、定量地区分长江和黄河沉积物,并可用于中国东部边缘海沉积物源的定量识别．δEuN-∑REEs是长江和黄河沉积物的源区气候条件和物质组成差异的综合体现,在沉积物由源区进入河流,再由河流进入海洋的过程中,δEuN—∑REEs关系基本保持不变,使得其最初的物源和气候信息得以保存,并继承下来． 相似文献
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若尔盖盆地RH孔有机碳同位素序列指示的古气候事件诊断 总被引：3，自引：1，他引：3
定量化是过去全球气候变化研究的必然趋势，突变事件的诊断是古气候定量化研究中极其重要的过程。本文运用Ｍ－Ｋ法和ｔ检验法对ＲＨ孔有机碳同位素序列进行了气候突变诊断研究。结果发现，近８００ｋａＢＰ来该区气候存在明显的突变，且突变开始于４７０ｋａＢＰ。进一步的研究发现４７０ｋａＢＰ开始的这一气候突变事件与青藏高原的构造隆升有密切的关系。 相似文献
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《中国科学:地球科学》2017,(8)
理解过去生态系统对气候变化的响应是评估未来气候变化影响的关键.在全新世气候逐渐变化背景下,萨赫勒-撒哈拉生态系统经历了由萨瓦拉到荒漠的突变.这样的非线性响应现象是否具有普遍意义仍需深入研究.本研究基于38个高质量的化石孢粉记录,系统分析了全新世中亚地区植被与气候的关系.结果显示全新世中亚地区的植被发生了两次大的突变,一次在早全新世(突变Ⅰ,"建立式"突变),另一次在晚全新世(突变Ⅱ,"崩溃式"突变),全新世中期则较稳定.然而这些植被突变无法与任何已知的气候突变事件相关联,并且不同区域发生植被转型的时间表现出异步性,显示出与当地降水量变化密切相关.这些植被突变可归因于植被响应轨道驱动的气候渐变的阈值效应.早全新世在轨道驱动下降水量增加,较湿润的区域首先达到植被"建立"的阈值,而在较干旱的区域明显较晚才达到该阈值.与之相反,晚全新世时在轨道驱动下降水量降低,首先在较干旱的区域达到阈值,导致植被"崩溃",而在较湿润地区延后达到阈值.另外,4.2kyr BP左右的干旱事件以及人类活动干扰对植被的崩溃退化也起到了一定的作用.上述认识得到了现代孢粉-气候关系分析以及生态系统模拟结果的支持.这些结果暗示未来气候变化一旦达到阈值将导致干旱生态系统产生突变. 相似文献
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洞庭湖流域气候变化特征(1961-2003年) 总被引：6，自引：0，他引：6
以22个气象站1961-2003年的气象观测数据为基础,对洞庭湖流域的气温、降水和参照蒸散量进行趋势与突变分析．从1970年开始,洞庭湖流域经历了一个缓慢而稳定的增温过程,1990s发生突变进入快速增温时期；尤其是是在春、冬季节,这种突变式的增温特征非常显著；秋季持续而稳定增温,而夏季气温并无明显变化．进入1990s,洞庭湖流域降水有明显增多,尤其是夏季降水突变式增加；与此同时,夏季暴雨频率也突变式增大,但是暴雨强度并无明显变化．1900s迄今,参照蒸散量持续而稳定的减少,夏季减少量尤为显著．全球变暖的区域响应,驱动洞庭湖流域水循环速度加快,夏季降水增多,而蒸发能力减弱,这是1990s洞庭湖流域洪水频发的主要气候因子． 相似文献
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全新世气候变化的动力成因，至今未有定论．大量地质证据揭示了全新世气候多次降温，并反映出与火山爆发有时问对应关系．现代气候观测证明了火山灰进入平流层滞留后随环流扩散成为太阳辐射的屏障层，从而导致地表降温．停留在地质火山爆发和伞新世气候在逐个点遥相关研究上，难以从宏观机制上加以认识．本文试图对地质火山影响古气候变化的定性推论与现代火山气候效应这两个环节，给予动力机制上的联系和分析．通过火山地质记录的现代气候效应类比，对地质火山数据进行集成，所反映的五次全新世强火山爆发集中期与地质记录的寒冷期／降温期／新冰期能够对应．对火山爆发集中期和平静期两种气候状况，通过三维大气环流模式进行气候数值模拟，评估火山灰产生的不同区域的降温效应．模拟结果表明，火山灰阳伞效应造成北半球年平均温度普遍降低，且具有明显的区域差异．高纬度降温幅度大于低纬度，夏季降温幅度大于冬季．全新世火山影响气候时空记录和火山灰敏感性气候试验为进一步探讨全新世气候变化成因提供重要的科学依据，也为最终认识现代气候系统变化以及对未来十年一百年尺度的气候预测提供重要的参照系． 相似文献
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复杂观测系统下的三维波动方程叠前深度偏移 总被引：1，自引：6，他引：1
波动方程三维叠前深度偏移是近年应复杂地质构造与地震岩性成像需求而发展的一项关键技术。此项技术与集群式并行机的结合，更是将其价格性能比较低至工业生产规模应用水平，然而，波动方程三维叠前深度偏移的实用化还需要诸如地震资料网络化、并行计算负载平衡等一系列配套技术。本文针对油田实际资料，试验了其应用波动方程三维叠前深度偏移的规则化技术，并结合地震炮集数据的特点，在自组装的集群式并行机上，解决了其节点间的负载平衡问题。本项工作有助于推近复杂观测系统下的地震数据实现三维波动方程叠前深度偏移。 相似文献
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Gudrun Richter Joachim Wassermann Martin Zimmer Matthias Ohrnberger 《Journal of Volcanology and Geothermal Research》2004,135(4):331-342
In this paper we present densely sampled fumarole temperature data, recorded continuously at a high-temperature fumarole of Mt. Merapi volcano (Indonesia). These temperature time series are correlated with continuous records of rainfall and seismic waveform data collected at the Indonesian–German multi-parameter monitoring network. The correlation analysis of fumarole temperature and precipitation data shows a clear influence of tropical rain events on fumarole temperature. In addition, there is some evidence that rainfall may influence seismicity rates, indicating interaction of meteoric water with the volcanic system. Knowledge about such interactions is important, as lava dome instabilities caused by heavy-precipitation events may result in pyroclastic flows. Apart from the strong external influences on fumarole temperature and seismicity rate, which may conceal smaller signals caused by volcanic degassing processes, the analysis of fumarole temperature and seismic data indicates a statistically significant correlation between a certain type of seismic activity and an increase in fumarole temperature. This certain type of seismic activity consists of a seismic cluster of several high-frequency transients and an ultra-long-period signal (<0.002 Hz), which are best observed using a broadband seismometer deployed at a distance of 600 m from the active lava dome. The corresponding change in fumarole temperature starts a few minutes after the ultra-long-period signal and simultaneously with the high-frequency seismic cluster. The change in fumarole temperature, an increase of 5 °C on average, resembles a smoothed step. Fifty-four occurrences of simultaneous high-frequency seismic cluster, ultra-long period signal and increase of fumarole temperature have been identified in the data set from August 2000 to January 2001. The observed signals appear to correspond to degassing processes in the summit region of Mt. Merapi. 相似文献
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Paul Francis Worthington 《Surveys in Geophysics》1975,2(3):313-366
Groundwater flow and storage in granular aquifers are much more amenable to analysis than in fissured reservoirs. The hydrological parameters used to describe the behaviour of a granular aquifer have been seen to be related to geophysical parameters in diverse water-bearing formations. This means that certain geophysical survey techniques are potentially useful as quantitative hydrogeological tools. Yet the study of these basic relationships and their subsequent field application have been disjointed and lacking in overal co-ordination. Consequently these quantitative hydrogeophysical procedures have not been applied to maximum advantage. The role of geophysics in quantitative studies of granular aquifers is reviewed in terms of the prediction of effective porosity and intergranular permeability from geophysical measurement. The potential usefulness of these methods manifests itself through the degree of correlation between hydrological and geophysical parameters observed from laboratory studies, borehole logging investigations or field survey data. Their application is exemplified through an ordered series of hydrogeophysical case histories. It is contended that the potential of geophysical methods in quantitative studies of this kind has by no means been fully exploited. 相似文献
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H. H. Guliyev Kh. B. Aghayev G. H. Hasanova 《Izvestiya Physics of the Solid Earth》2016,52(6):836-843
The method of determining the values of elastic moduli of the third order of sedimentary series of rocks is developed based on a complex of well-logging data. The calculation algorithm is based on the theory of elastic wave propagation in deformed solids, seismic-geological modeling, and the cluster analysis of well data on artificial neural networks. The elastic moduli of sedimentary series of rocks of oil- and gas-bearing structures of the Gunashli of the South Caspian Basin (SCB) are determined using the offered method. The numerical values of Poisson’s ratio are also determined for these rocks. The inaccuracies of the results obtained within the simplified theories are revealed in this example without considering the current geodynamic changes. 相似文献
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Abstract A new series of detailed observations of the Coma cluster of galaxies has been undertaken with the aim of better specifying the intergalactic gas component through high dynamic range, combined-telescope observations of the radio emission from the cluster which detect both the cluster-scale and galaxy-scale emission. By combining these multi-frequency radio maps with a Faraday rotation probe experiment using cluster and background sources, and the published X-ray data, we have been able to estimate the intracluster magnetic field strength independently of the usual assumptions of equipartition. The result is approximately 2 microgauss. We compare the X-ray and radio distributions in detail, and describe how our combined results suggest that acceleration of the relativistic electrons occurs in situ, and we suggest that the conditions in the cluster provide good physical arguments to support this. 相似文献
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Time series analysis of optical remote sensing data for the mapping of temporary surface water bodies in sub-Saharan western Africa 总被引：2，自引：0，他引：2
A map of temporary small water bodies (TSWB) at 1 km resolution was derived for the arid, semi-arid and dry sub-humid regions of sub-Saharan western Africa where the spatio-temporal distribution of actual surface water occurrence exhibits high inter- and intra-annual variability. Water bodies and humid areas have been mapped and characterized by the analysis of 10 daily small water bodies (SWB) maps based on SPOT VEGETATION (VGT) data spanning the period January 1999–September 2007. Further analysis of the SWB time series provided additional information about the seasonal recurrence of water bodies as well as their hydrological function. A map derived from a continuous time series assures the inclusion of temporary features, a clear advantage compared to other datasets, which are based on several single date observations. The method described in this paper targets at a rapid creation of TSWB maps based on the SWB time series for different time intervals and regions.An accuracy assessment has been carried out with a stratified random sampling approach and a one-stage cluster analysis that relies on high-resolution satellite data to verify the detected water bodies. The overall accuracy, considering only the commission error, is 95.4% for the whole study region, with best results in the arid and semi-arid climate zone. The method to map water bodies delivers satisfactory results, particularly for sparsely vegetated areas as well as flat areas of the study region. In more humid, more vegetated areas and in mountainous areas, the possibility of false detections increases due to surface characteristics. 相似文献
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Tackling mass redistribution phenomena by time-dependent GRACE- and terrestrial gravity observations
Time variable gravity field models derived from the satellite mission GRACE have been demonstrated to be consistent with water mass variations in the global hydrological cycle. Independent observations are provided by terrestrial measurements. In order to achieve a maximum of reliability and information gain, ground-based gravity observations may be deployed for comparison with the gravity field variations derived from the GRACE satellite mission. In this context, the data of the network of superconducting gravimeters (SG) of the ‘Global Geodynamics Project’ (GGP) are of particular interest. This study is focused on the dense SG network in Central Europe with its long-term gravity observations. It is shown that after the separation and reduction of local hydrological effects in the SG observations especially for subsurface stations, the time-variable gravity signals from GRACE agree well with the terrestrial observations from the SG station cluster.Station stability of the SG sites with respect to vertical deformations was checked by GNSS based observations. Most of the variability can be explained by loading effects due to changes in continental water storage, and, in general, the stability of all stations has been confirmed.From comparisons based on correlation and coherence analyses in combination with the root mean square (RMS) variability of the time series emerges, that the maximum correspondence between the SG and GRACE time series is achieved when filtering the GRACE data with Gaussian filters of about 1000 km filter length, which is in accordance with previous publications.Empirical Orthogonal Functions (EOF) analysis was applied to the gravity time series in order to identify common characteristic spatial and temporal patterns. The high correspondence of the first modes for GRACE and SG data implies that the first EOF mode represents a large-scale (Central European) time-variable gravity signal seen by both the GRACE satellites and the SG cluster. 相似文献
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趋势转折是地壳形变变化的一个重要信息,为定量、精确地提取地壳形变观测资料的趋势转折点,基于改进的有序聚类分析法,采用时窗滑动的方法,提取时间序列的趋势转折点,并编制了相应的程序.以新源地震台地倾斜南北向1992～2006年的观测数据为例,以4年窗长、2年步长滑动计算其趋势转折点.研究结果表明：（1）采用改进的有序聚类分析法提取时间序列的趋势转折点具有明确的统计意义,可减少人为判断的主观和任意性.（2）该方法算法简单,易于实现,可用于日常的地壳形变观测资料的分析预报工作.（3）新源地震台地倾斜南北向观测数据计算结果表明,在2001年之前,趋势转折比较频繁,变化也比较明显,而在2001年之后,趋势转折较少,变化更接近线性. 相似文献
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A novel methodology for the solution of the 2D shallow water equations is proposed. The algorithm is based on a fractional step decomposition of the original system in (1) a convective prediction, (2) a convective correction, and (3) a diffusive correction step. The convective components are solved using a Marching in Space and Time (MAST) procedure, that solves a sequence of small ODEs systems, one for each computational cell, ordered according to the cell value of a scalar approximated potential. The scalar potential is sought after computing first the minimum of a functional via the solution of a large linear system and then refining locally the optimum search. Model results are compared with the experimental data of two laboratory tests and with the results of other simulations carried out for the same tests by different authors. A comparison with the analytical solution of the oblique jump test has been also considered. Numerical results of the proposed scheme are in good agreement with measured data, as well as with analytical and higher order approximation methods results. The growth of the CPU time versus the cell number is investigated successively refining the elements of an initially coarse mesh. The CPU specific time, per element and per time step, is found out to be almost constant and no evidence of Courant–Friedrichs–Levi (CFL) number limitation has been detected in all the numerical experiments. 相似文献