2013年海洋和大气环流异常及对中国气候的影响     

司东  袁媛  崔童  孙冷  王东阡  柳艳菊  郭艳君  王遵娅 《气象》2014,40(4):494-501

本文对2013年海洋和大气环流异常特征进行分析,讨论这些异常特征对中国气温和降水的主要影响。结果表明：2012/2013年冬季,北极涛动持续维持负位相,500 hPa位势高度场上,欧亚大陆中高纬环流呈“两槽一脊”的环流形势,乌拉尔山的高压脊持续偏强,而东亚槽也异常偏强,导致全国平均气温较常年同期偏低。季内,西伯利亚高压强度变化显著,与之相对应,我国气温季内阶段性变化大,前冬冷、后冬暖。进一步研究表明,前秋北极海冰的大幅偏少是造成东亚冬季风偏强的重要原因。2013年冬季至夏季,赤道中东太平洋海温异常偏低而海洋性大陆至西太平洋海温异常偏高,受此影响,夏季西太平洋副热带高压位置明显偏北,导致我国北方夏季多雨。与此同时,受西太平洋副热带高压下沉气流的控制,我国南方大部高温持续。2013年南海夏季风爆发偏早两候,结束偏晚4候,强度偏弱。  相似文献   

Late glacial and Holocene environmental change in the Lake Baikal region documented by oxygen isotopes from diatom silica   总被引：4，自引：0，他引：4  

David W. Morley  Melanie J. Leng  Anson W. Mackay  Hilary J. Sloane 《Global and Planetary Change》2005,46(1-4):221

We investigate late glacial and Holocene climate change recorded in Lake Baikal using the oxygen isotope composition of diatom silica (δ¹⁸O_DIAT). Evaporation from the lake is minor, and the temperature fractionations of δ¹⁸O are unable to explain variations in the δ¹⁸O_DIAT record alone. Isotopically, low meltwater input from glaciers may have some influence on δ¹⁸O_DIAT, but the assumed periods of climatic warming and wastage do not coincide with large shifts in δ¹⁸O_DIAT. There is a gradual oxygen isotope lowering from 27.0‰ to 20.6‰ over the late glacial, while, during the Holocene, δ¹⁸O_DIAT values return to relatively high values. Previous studies of the modern oxygen and hydrogen isotope composition of Lake Baikal's inputs reveal that fluvial input to the lake's North Basin are isotopically lower than fluvial input from South Basin rivers. This north–south gradient of river δ¹⁸O and δD is mainly due to the greater input from isotopically low winter precipitation in the north and isotopically higher summer precipitation in the south. As a result, the δ¹⁸O_DIAT record from Lake Baikal can at least in part be explained by varying input from these sources related to seasonal changes in precipitation. Changes in atmospheric conditions may have a role in altering seasonality and the distribution of precipitation over Lake Baikal's catchment. A feedback mechanism is well known linking higher Eurasian spring snow cover extent (ESSC) to the development of anticyclonic conditions and low precipitation the following summer in the areas south of Lake Baikal. A simultaneous increase in the importance of depleted water (snowmelt) input from the north and decreased enriched summer precipitation in the south is needed to explain depletions in δ¹⁸O of lake water and subsequently δ¹⁸O_DIAT during colder periods. The opposite of this situation is required to enrich lake water during warmer periods. The analysis of δ¹⁸O from diatom silica is a useful proxy for environmental change, especially in lakes, like Lake Baikal, where carbonates are absent or diluted. However, analysis must be based on near pure diatom samples as even trace amounts of silt can have a dominating effect on δ¹⁸O_DIAT values.  相似文献   

基于裂隙扩展的多级岩质边坡开挖卸荷破坏路径分析     

王川  冷先伦  张占荣  杨闯  陈健 《岩土力学》2023,(4):1190-1203

开挖卸荷作用下裂隙岩体边坡的破坏模式与路径分析是边坡工程灾害研究的热点之一,准确识别边坡的潜在破裂路径对工程安全施工和支护优化设计具有重要意义。依据断裂扩展分析方法,将裂隙扩展判别的理论方法开发并应用于数值模拟分析中,通过裂隙尖端应力强度因子计算、裂隙扩展模式识别、裂隙起裂角演算、裂隙扩展交汇等技术实现了岩体中断续裂隙的起裂、扩展与贯通演化过程的快速模拟;以某高速公路沿线裂隙岩体路堑边坡为对象,采用提出的模拟方法分析了多级开挖卸荷作用下坡体裂隙的扩展机制与边坡的破坏路径。结果表明：裂隙岩体边坡从上至下多级开挖过程中,坡肩裂隙首先起裂,并通过拉张型扩展逐渐发展为优势裂隙;随着边坡下挖,优势裂隙沿坡面向下逐步发生拉张/剪切混合型扩展并与既有裂隙交汇,在边坡中上部形成阶梯状扩展破坏路径;裂隙扩展至边坡下部及坡脚后扩展模式由拉张/剪切混合型转化为剪切型,并最终以弧形剪切面从坡脚出露。研究揭示了裂隙岩体边坡多级开挖卸荷作用下上部阶梯状拉张/剪切混合型破裂-下部弧形剪切型破裂的复合破坏模式,可为边坡工程支护设计和施工稳定性控制提供新思路。  相似文献   

河南省卢氏县八宝山铜矿床地质特征及成因     

冷小明 《地质与勘探》2023,59(1):70-84

河南省卢氏县八宝山岩体属晚侏罗世中酸性浅成小岩体。结合前人研究成果,通过研究该矿区地质特征和物化探成果,结合本次普查中对成矿理论的实地钻探工程验证,研究认为八宝山矿床类型为斑岩-矽卡岩型矿床,且矿床由内向外具有明显的高中低温分带性,矿床三种分带围绕岩体呈环状分布。成矿模式为以岩体中心相为中心至外侧边缘相,依次为斑岩型-矽卡岩型-热液型三条环带模式。研究区最新提交备案成果（普查）：铁矿石量2389.10万吨,硫铁矿石量334.00万吨,铜金属量108962,提交一中型铜矿床。通过研究该矿床成因及成矿模式,为研究区资源储量提升找到工作靶区,也为寻找相同类型矿床或者附近隐伏矿床提供借鉴依据。  相似文献   

鄂尔多斯盆地庆城地区延长组7段致密油特征及油源分析     

屈童  高岗  梁晓伟  孙明亮  尤源  李涛涛  冯顺彦  刘艳妮  费国勇 《地质论评》2023,69(4):1313-1328

鄂尔多斯盆地三叠系延长组7段(长7段)半深湖—深湖相优质油源岩是油气的重要来源,包括黑色页岩和暗色泥岩,作为盆地重要的供烃源岩一直是研究的热点。为了明确不同烃源岩的贡献及油气来源,通过对庆城地区长7段致密油特征进行分析,对原油进行精细划分,并对源岩有效性进行分析,进一步明确油源对应关系,研究表明,庆城地区长7段黑色页岩和暗色泥岩均对油气成藏有贡献,其中黑色页岩贡献最大,长7₃段暗色泥岩次之,长7₂和长7₁段暗色泥岩贡献较小;原油为低密度、中—低黏度和低凝固点的轻质油。根据生标物特征将原油划分为3类,A类原油具有低C₃₀重排藿烷/C₂₉藿烷、低C₂₉Ts/C₂₉藿烷、低Ts/Tm的特征,由黑色页岩贡献,主要分布于长7₁段;C类原油具有高C₃₀重排藿烷/C₂₉藿烷、高C₂₉Ts/C₂₉藿烷、高Ts/Tm的特征,主要由暗色泥岩贡献,...  相似文献   

A high-resolution Late Glacial to Holocene record of environmental change in the Mediterranean from Lake Ohrid (Macedonia/Albania)     

Jack H. Lacey  Alexander Francke  Melanie J. Leng  Christopher H. Vane  Bernd Wagner 《International Journal of Earth Sciences》2015,104(6):1623-1638

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SWAN系统中雷达反射率因子质量控制算法及其应用   总被引：4，自引：0，他引：4  

吴涛  万玉发  沃伟锋  冷亮 《气象科技》2013,41(5):809-817

介绍了SWAN系统中雷达反射率因子质量控制算法原理,包括数据预处理、孤立噪声回波过滤、超折射回波抑制3部分.数据预处理将原始雷达资料转换为统一的RD20格式,并检测数据质量.孤立噪声回波过滤包括双向搜索、回波特征量过滤法.超折射（Anomalous Propagation,AP）回波抑制采用模糊逻辑原理.介绍算法配置参数,通过对比分析武汉、随州、西安雷达AP识别因子概率分布图可知,三者是类似的,表明默认参数的适用性.评估表明,该方法可过滤掉大部分AP回波,缺点是未能识别部分远距离AP回波以及错误识别部分降水回波.  相似文献   

THE STRATEGIC STRAIT WITH SPECIAL REFERENCE TO THE MALACCA STRAITS1     

Allan Chia  Lee Yong Leng 《Singapore journal of tropical geography》1987,8(2):97-113

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Bulk organic δ13C and C/N ratios as palaeosalinity indicators within a Scottish isolation basin     

Elizabeth A. V. Mackie  Melanie J. Leng  Jeremy M. Lloyd  Carol Arrowsmith 《第四纪科学杂志》2005,20(4):303-312

Microfossils in isolation basin sediments are frequently used to reconstruct sea‐level change, but preservation problems and non‐analogue situations can limit their usefulness. Here we investigate the potential of stable carbon isotopes (δ¹³C) and C/N ratios from bulk organic matter, as an alternative proxy of salinity within isolation basin sediments from a basin in northwest Scotland. Within the Holocene sediment δ¹³C and C/N are determined largely by the mean weighted values of the predominant source of the organic material. Analysis of modern materials and comparison with the diatom record shows that the marine parts of the sequence are dominated by high δ¹³C and variable C/N. In the fresh water sequences the organic material is a mixture of both freshwater aquatic and terrestrial plant input that have relatively low δ¹³C and high C/N. The application of δ¹³C and C/N ratios in the studied basin in general follow the environmental change recorded by the diatoms and shows the potential of bulk organic matter in the investigation of salinity change in isolation basins. Copyright © 2005 John Wiley & Sons, Ltd.  相似文献   

SOME GEOPOLITICAL IMPLICATIONS OF UNCLOS III* CONTINENTAL SHELF PROBLEMS     

Lee Yong Leng 《Singapore journal of tropical geography》1981,2(1):32-39

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