利用树轮资料重建青海都兰地区过去1835年的气候变化

根据青海都兰地区树木年轮样本,建立了上前我国最长的年轮年表序列（１８３５a）,系 统地与所在地区气候资料进行了综合分析。通过响应函数计算得出,该年表对温度因子的反映更为第三一些。在响应面分析中发现,温度、降水与年轮宽度的关系呈现出随温度和降水的不同而不同。在温度低而降水量少的情况下,其线性相关性明显;但在温度较高和降水量较多时,树轮与两要素间的关系就显得不明显。另外,还对该年表玮秋季平均温度的关系进     

利用钻孔温度梯度重建过去气候变化进展

地球表面的温度信号向地下传播并影响地下温度剖面,这种温度剖面可从钻孔中测量,通过分析可重建过去表面温度变化.虽然认识到表面温度变化对地下温度和热流的影响已有很长时间,但仅在20世纪80年代以后钻孔温度剖面才被广泛应用于气候变化研究.钻孔气候方法与其他重建过去气候的近似方法不同,因为它是基于温度剖面测量与过去气候,即地表温度(GST)、重构参数的直接物理联系之上的.钻孔温度气候研究方法已被证实可以重建过去地表温度趋势,并且最终可结合表面气温序列估计其预观测平均值(POMs).钻孔温度剖面并不是地表温度的代用指标,而是地球大陆表面能量平衡的直接测量.这种地下的信号通过热扩散衰减非常快,因而对从地下温度测量数据中提取过去气候变化信息的方法施加了一个物理限制.描述由钻孔中测量的温度—深度剖面来重建GST历史的基本特征及问题.     

青藏高原表土孢粉定量重建的气候参数探讨

孢粉在古环境研究中具有重要价值,尤其是在重建古气候方面,既可以定性地恢复过去的植被类型变化,也能定量地重建气候变化规律,是古气候研究中最常用、较可靠和较成熟的环境代用指标。现代类比法是探讨表土孢粉与气候定量关系的方法之一,适用性较为广泛。本文利用青藏高原及其毗邻地区495个现代表土样点的孢粉谱,及现代气象站点器测资料,采用现代类比法得到气候参数的模拟值,并分析模拟值与气候参数观测值之间的关系。结果表明:相关性最高的气候因子是年均降水(r=0.894),其次为年均相对湿度(r=0.863)和年均蒸发量(r=0.801),最低的是干燥度(r=0.18)。因此在重建古气候时降水的可信度较高,相对湿度和蒸发量也具有一定的可信度。并选用相关性较好的年均降水指标,分析其与11个孢粉类型之间的相关性,然后将相关性较高的孢粉组合与降水之间建立孢粉-气候函数模型,用以重建该地区过去气候变化。     

Primary Study on Quantitative Reconstruction of Middle-Late Eocene Climate in Jianghan Basin

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江汉盆地始新世中、晚期古气候定量重建初探

依据江汉盆地明钾1孔中、晚始新统系统的孢粉资料, 应用化石孢子花粉亲缘植物的生态位估算孢粉组合所反映的古气候特征.气候参数曲线的变化趋势显示江汉盆地始新世中期气候参数与现今北纬2 2°~ 2 6°的数值相接近, 为中-南亚热带湿润半湿润气候.晚期气温较前期低1~ 4℃, 相当于现今北纬2 3°~ 2 8°处的数值, 为北-中亚热带气候.但是, 气候构型与现今截然不同, 具有气温高、年较差小、降水波动大的特点.始新世中期1月均温比今高5~ 9℃, 表明冬季风作用尚不明显, 晚期略显冬季风的影响.气候的降温发生在孔深2 10 0m处, 主要表现为1月均温的下降和年较差增长, 因而孢粉组合中落叶阔叶树种增多.年降水量波动强烈, 一般于30 0~ 170 0mm之间, 这有利于盐类矿物的迁移和堆积.降水量低于10 0 0mm时, 麻黄灌木花粉增多, 且与膏盐堆积深度相一致.高山深盆的干热环境是本区盐类矿物沉积的主要原因, 年降水量波动强烈且偏低, 有利于盐类的持续堆积, 从而有别于现今西北地区的盐类堆积.      

Reconstruction of the Past Climate From Tree Rings Over Western Himalaya, India

RECONSTRUCTION OF THE PAST CLIMATE FROM TREE RINGS OVER WESTERN HIMALAYA, INDIA     

气候变化适应对策的评价方法和工具

气候变化影响和适应对策方法评估的研究目的主要是建立和应用先进有效的分析工具和评价方法对气候变化脆弱性和适应对策进行科学评估. 因此需要了解当前已经在自然资源和环境研究中广泛使用的决策分析工具,掌握和了解各种适应对策评估工具的关键特性及其优缺点. 首先介绍各种有关适应对策的定义及两大类适应评估方法途径, 同时举例介绍不同方法在气候变化影响和适应评估研究中的应用. 常规的适应对策评估分析主要以政府间气候变化专业委员会(IPCC)气候变化影响和适应对策评估技术指南中的方法工具为代表, 另一种适应对策研究则致力于改善各种对气候变化敏感系统的适应能力和复原能力. 文中对各种适应对策评估方法和工具进行了介绍和讨论,并提出气候变化适应研究的新方向.     

黄土高原地区古气候定量化研究方法评述

定量化重建黄土高原地区古气候,是黄土研究的新方向和大趋势。本文主要从土壤磁化率、植物孢粉、植物硅酸体和稳定同位素等替代性指标方面回顾了国内外对黄土高原地区古气候定量化研究的现状,并对研究中存在的问题进行了讨论。相关的研究结果表明,黄土高原地区的古气候定量化研究取得了积极的成果,但还仍处在初步阶段。由于指标本身存在局限性或指标与气候要素之间机理尚不十分清楚,所获得的定量化结果并不能令人十分满意。提出今后定量化重建古气候研究的重点是要进一步加强对黄土高原现代生态过程的研究,清楚地认识各指标与气候要素之间的机理和联系,建立可信的相关函数。希望对这方面的研究有所裨益。     

岩土力学数值分析方法研究

随着岩土工程领域的不断扩展与延伸,岩土力学数值分析方法得到了迅速发展,出现了各种各样的数值分析方法。将岩土力学常用的数值分析方法分为连续变形分析方法与非连续变形分析方法两大类,对各种方法的研究现状和最新进展进行了评述,着重介绍了各种方法的优缺点,并提出了解决问题的思路、方法和建议。     

Comparison of the Methods of Rock-Microscopic Grain-Size Determination and Quantitative Analysis

This study is a methodological investigation of the textural constituents of one- and multicomponent magmatic, sedimentary, and metamorphic rocks as well as artificially cemented composites (concrete, ceramics, etc.) in view of both quantity and grain-size distribution. After the theoretical comparison of the known procedures available (e.g., point counting, measurement along reference lines, planimetry, etc.) the most convenient measurement technique is selected, complemented, then characterized. Most convenient for the dual purpose, with respect to efficiency and standard deviation, is the simple measurement with a scaled cross hairs eyepiece along a reference line. The basic data obtained in this way can be presented both in tables and diagrams. In the area under the cumulative curve demonstrable in the semilogarithmic grain-size-frequency coordinate system, well-known in sedimentology, size-distribution of the constituents can be presented. On the grounds of the individual character of the exact data described, assumptions on the properties, degree of homogeneity, and origin of the material can be drawn. The optimal procedure selected is suitable for computer processing. The texture of the rocks can be characterized with the variable accuracy desired, any unnecessary excess work, and oversize measurement can be avoided. At the same time, an opportunity is opened to check the reliability of earlier measurements performed with different methods or on limited amounts of material (e.g., drill core).     

Analysis of Wedge Stability Using Different Methods

Summary The stability problem of a rock slope containing a wedge resting on two intersecting discontinuities is of great interest in rock slope engineering. It is a statistically indeterminate problem with two extra unknowns according to the force (stress) equilibrium analysis. The widely used limit equilibrium methods in practice assume that the directions of the shear forces acting on the two discontinuities are parallel to their line of intersection. The validity of this assumption, however, has not been verified theoretically. This paper presents a general limit equilibrium method that determines the directions of the shear forces by using Pans Maximum principle and an upper bound method that applies the classic upper bound theorem of limit analysis to avoid making extra assumptions. The formulations of the two methods are derived. A non-symmetric wedge and a symmetric wedge are analyzed using the two derived methods. To further explore the influence on stability due to the direction of the shear force acting on the two discontinuities, three-dimensional finite-element analyses are also conducted. The results are compared and discussed.     

岩土力学数值方法的应用及发展

本文为在第三届全国岩土力学数值分析与解析方法讨论会上的专题综述报告。文中就提交本届会议有关数值方法在岩土力学中的应用的论文以及数值方法的应用及发展的若干问题作一综合报导与述评。     

气候变异与气候变化对水循环影响研究综述

阐述了水循环及其受气候变化与人类活动影响的途径与特性，介绍并指出了在这一领域的研究方法及存在的问题，综述了我国一些地区和流域的初步研究成果。     

基于共存分析法和叶缘分析法重建中国渐新世年均温

渐新世全球气候总体上发生了降温,代表着地球新生代早期的一个"冰室"。植物对气候变化反应敏感,作为地质时期的产物,植物化石能够反映当时陆地气候的变迁。本文利用共存分析法(Coexistence Approach,CA)对中国5个渐新世植物群的年均温进行了恢复,并利用叶缘分析法(Leaf Margin Analysis,LMA)对其中木本双子叶植物不少于15种的4个植物群年均温进行了分析。两类方法的推测值整体表现为CA的年均温相对高于LMA值,其中叶缘分析法东亚模型得出的年均温高于中国模型值。通过对能影响两类方法结果的因素分析,推测CA恢复的值能更好地代表化石点当时的年均温,咸水河组下段植物群为13.3~15.6℃,杨连屯组大桥段植物群为12.1~19.4℃,三合植物群为14.3~16.8℃,景谷植物群为19.7~23.7℃,宁明组植物群为22.0~23.6℃。由于CA恢复的年均温都高于当地现在的年均温,推测渐新世时,虽然全球温度自始新世以来整体相对降低,但还是比现在温暖。     

古大气CO2浓度重建方法技术研究现状

温室气候引起的全球气候变暖越来越引起人们的关注,大气中不断上升的CO2浓度被认为是导致气候变暖的主要因素.地史时期大气CO2浓度变化与温室气候可能存在类似的关系,可提供参考,因而古大气CO2浓度重建是首要任务.总结近年来古大气CO2浓度重建的进展,重点介绍GEOCARB模型模拟、植物叶片气孔参数和同位素指针的方法和技术.GEOCARB模型是反映全球古大气CO2浓度长期变化的碳相关模型;气孔参数方法是使用气孔比例来估计古大气CO2浓度;同位素指针包括成壤碳酸盐、浮游植物有机质生物标记物、钙质浮游有孔虫、古苔藓植物等,其中成壤碳酸盐碳同位素方法使用最为广泛.国内只是在叶片参数研究方面有一些进展,古大气CO2浓度重建工作任重而道远.     

Paleoenvironmental Evolution of the Beilun River Estuary, Northwest South China Sea, During the Past 20,000 Years Based on Diatoms

The paleoenvironmental history of the Beilun River estuary on the coast of Beibu Gulf in the northwest South China Sea is reconstructed based on fossil diatoms, isotopic dating, sedimentary grain size data, mineralogy and geochemistry in three sediment core samples. Results show that the estuary has experienced significant environmental changes since deposition began about 20,000 yr ago. Freshwater runoff of the Beilun River initially was strong. However, the freshwater runoff reduced significantly after a transgressive event. Subsequently the estuary’s position began to migrate to the northeast. At the end of the Late Pleistocene the estuary shifted gradually towards the southwest. In the Early-Mid Holocene, the estuary’s geomorphology was shaped by seawater transgressing into the ancient river channel. The basin was filled continuously but slowly to form the present Beilun River estuary. Holocene transgression in this area could be divided roughly into three stages, including oscillation period 1, the maximum transgression period, and oscillation period 2.     

Climate Reconstruction based on Pollen Analysis in Inner Mongolia, North China from 51.9 to 30.6 kaBP

The palynomorph assemblage of lake sediments younger than 51.9 kaBP from Wulagai Gobi in Inner Mongolia was analyzed to reconstruct the vegetation and climate.From 51.9 to 30.6kaBP,the vegetation was arid to semi-arid grassland with only slight changes.According to the palynomorphs,trees and shrubs were very rare.The large number and diversity of algae indicate the presence of a lake.Quantitative climatic conditions were reconstructed using the Best Analogues Method.The results indicate that the annual mean temperature was higher than that at present.The combination of temperature and annual precipitation suggests a change in the climate from cool dry to warm dry and then cool humid.Our results show that the annual precipitation values were mostly higher than that at present but were lower than 400 mm.It infers that the study area was already within the arid to semi-arid regions but with a stronger influence of the summer monsoon during 51.9to 30.6 kaBP than at present.With slight differences mainly in time scale,the changing trend of the annual temperature curve is consistent with the other climatic records from Antarctica,Greenland,Hulu Cave(East China),and the Tibetan Plateau during the last glacial period.From 30.6 kaBP to present,very few palynomorphs were detected in the samples.Hence,no information about the vegetation and climate could be extracted.Combined with other studies during Late Pleistocene,we presume that the reason for the lack of pollen during this period was caused by an abrupt temperature fall after 30.6 kaBP or that the lacustrine conditions were unsuitable for pollen deposition.It was probably incurred by the oxidation on land prior to deposition.But for those samples only with algae,it might be caused by the fact that algae could finish their life history in a very short time in a seasonal lake.     

Quantitative Electron Microprobe Analysis of Silicates Using Energy-Dispersive X-Ray Spectrometry

The advantages of using a lithium-drifted silicon X-ray detectorinstead of conventional Bragg spectrometers in microprobe analysisinclude simplicity and speed of operation. Also electron beamdamage to minerals can be almost eliminated, owing to the lowprobe current required. A procedure for quantitative analysisis outlined here, and its scope and limitations are discussed,with special reference to silicate analysis. Analyses of 34silicates independently analysed by chemical methods and conventionalprobe analysis are given. Above about 0.2 wt. per cent (element)systematic differences between energy-dispersive and conventionalprobe results are hardly significant. There are some discrepanciesbetween probe and chemical data, probably mostly due to errorsin the latter (e.g. high A12O3 and low FeO). Concentrationsbelow 0.2 per cent but above the theoretical limit of detectionare sometimes not recorded. This is presumed to be due to slightover-correction for background, which could be rectified bya more complicated background correction procedure.