Boreal temperature variability inferred from maximum latewood density and tree-ring width data, Wrangell Mountain region, Alaska   总被引：3，自引：0，他引：3  

Nicole K. Davi  Gordon C. Jacoby  Gregory C. Wiles 《Quaternary Research》2003,60(3):252-262

Variations in both width and density of annual rings from a network of tree chronologies were used to develop high-resolution proxies to extend the climate record in the Wrangell Mountain region of Alaska. We developed a warm-season (July–September) temperature reconstruction that spans A.D. 1593–1992 based on the first eigenvector from principal component analysis of six maximum latewood density (MXD) chronologies. The climate/tree-growth model accounts for 51% of the temperature variance from 1958 to 1992 and shows cold in the late 1600s–early 1700s followed by a warmer period, cooling in the late 1700s–early 1800s, and warming in the 20th century. The 20th century is the warmest of the past four centuries. Several severely cold warm-seasons coincide with major volcanic eruptions. The first eigenvector from a ring-width (RW) network, based on nine chronologies from the Wrangell Mountain region (A.D. 1550–1970), is correlated positively with both reconstructed and recorded Northern Hemisphere temperatures. RW shows a temporal history similar to that of MXD by increased growth (warmer) and decreased growth (cooler) intervals and trends. After around 1970 the RW series show a decrease in growth, while station data show continued warming, which may be related to increasing moisture stress or other factors. Both the temperature history based on MXD and the growth trends from the RW series are consistent with well-dated glacier fluctuations in the Wrangell Mountains and some of the temperature variations also correspond to variations in solar activity.  相似文献   

Tree-ring dated landslide movements and their relationship to seismic events in southwestern Montana, USA     

Paul E Carrara  J.Micheal O’Neill 《Quaternary Research》2003,59(1):25-35

To determine periods of incremental landslide movement and their possible relationship to regional seismic events, the tree-ring records of 32 tilted and damaged conifers at three sites on landslides in the Gravelly Range of southwestern Montana were examined. Several signs of disturbance in the tree-ring record indicating landslide movement were observed. Commonly, the tree-ring record displayed a marked reduction in annual ring width and/or the reaction wood formation. The tree-ring records from the three landslide sites indicate multiple periods of movement during the 20th century. Many of the periods of movement indicated by the strongest signals (most trees) at the sites occurred the year following significant earthquakes in the region. Those seismic events for which evidence in the tree-ring record was found at one or more of the three sites are the 1983 Borah Peak, 1959 Hebgen Lake, 1935 Helena, 1925 Clarkson, and 1908 Virginia City earthquakes. This study suggests that many of the landslide movements were triggered by, or are coincident with, earthquakes as much as 200 km from the study area.  相似文献   

采用基础摩擦隔震房屋高宽比限值的研究   总被引：12，自引：3，他引：12  

李宏男  王苏岩 《地震工程与工程振动》1997,17(3):73-76

大量的试验结果和地震经验表明，采用基础隔震方法能有效地提高建筑物的抗震能力，但建筑物的高度在什么范围，即建筑物的高宽比在什么范围内才适合采用这种方法，仍然是一个有待解决的课题。本文对采用基础滑移隔震多层砌体房屋在实际地震作用下的抗倾覆高宽比限值进行了研究，利用Ｗｉｌｓｏｎ－θ数值积分方法计算，得到了多层砌体房屋的高宽比限值的统计值。其数值结果可供编制建筑隔震设计规程参考。  相似文献   

天山北坡中部不同海拔高度雪岭云杉树轮宽度气候响应对比分析     

喻树龙  袁玉江  秦莉  尚华明  张同文  陈峰  张瑞波  范子昂 《沙漠与绿洲气象(新疆气象)》2016,10(3):30-38

利用天山北坡中部沙湾地区两个坡面随海拔高度采集的雪岭云杉树芯样本,建立了13个树轮宽度年表。分析结果表明,2个坡面年表特征值随海拔高度的变化而不同,不同海拔树轮宽度对气候因子的响应呈现规律性。高低海拔采样点在生长季前对气候因子的响应相同,而在生长季则呈相反的响应。在生长季,高海拔采样点随海拔的升高,树轮宽度对气温的响应降低。不同坡面间受小生境的干扰较大,坡度较小的大鹿角湾高海拔采样点主要受气温的影响,而在坡度较大的石头沟高海拔采点则对降水有更明显的响应。沙湾树轮宽度年表对PDSI指数的响应与大尺度范围的树轮响应一致,即与PDSI呈正相关,低海拔区域响应最显著。主成分分析表明,在同一坡面树轮宽度年表的前3个主分量可以反映因海拔高度变化气候因子对树木年轮生长的影响。2个坡面树轮宽度年表的第一主分量表征持续干旱对整个坡面的影响。  相似文献   

Study on the Relationship between Large Volcanic Eruptions and Temperature Variation Based on Tree-Ring Data in the Eastern Tibetan Plateau during the Past Millennium   总被引：1，自引：0，他引：1  

Li Mingqi  Shao Xuemei 《地球科学进展》2016,31(6):634-642

Volcanic eruptions can significantly cool the global troposphere on the time scales from several months up to a decade due to reflection of solar radiation by sulfate aerosols and feedback mechanisms in the climate system. The impact of volcanic eruptions on global climate are discussed in many studies. However, few studies have been done on the impact of volcanic eruption on climate change in China in the past millennium. The 1300-year and 600-year temperature series were reconstructed based on the six tree-ring temperature proxy data in northeastern and southeastern Tibetan Plateau, respectively. Three warm periods occurred in 670-920,1000-1310 and 1590-1930, and three cold periods happened at 920-1000,1310-1590 and 1930-2000 in the northeastern Tibetan Plateau. There were two obviously warm periods (1385-1450 and 1570-1820) and two cold periods (1450-1570 and 1820-2000) in southeastern Tibetan Plateau. Contrasting with volcanic eruption chronology, we analyzed the relationship between volcanic activity and temperature variation in the eastern Tibetan plateau during the past millennium using Superposed Epoch Analysis (SEA) method. The results indicated that the temperature decreased one year after large volcanic eruptions located beteen 10°S and 10°N in latitude in northeastern Tibetan Plateau and two years in southeastern Tibetan Plateau. The volcanic eruptions occurred at different latitudes have different impacts on the temperature variations, which may be caused by regional difference, the nature of the eruption, the magnitude of the resulting change in incoming solar radiation, prevailing background climate and internal variability, season, latitude, and other considerations.  相似文献   

Failure Pressure Analysis of Corroded Moderate-to-High Strength Pipelines     

苏晨亮  李昕  周晶 《海洋工程》2016,(1):69-82

Based on the elastic-plastic, large-deformation finite element method, burst capacity of steel pipeline with longitudinal corrosion defect subjected to internal pressure is studied. The appropriate stress-based criterion is used to predict the failure pressure of finite element model of corroded pipeline under internal pressure. By considering the pipe steel grades and geometries of corrosion defects, a series of finite element analyses is conducted. The effects of corrosion depth, length and width on burst capacity are also discussed. A specific failure pressure solution for the assessment of corrosion defects in moderate-to-high strength pipeline is proposed on the base of numerical results. The failure pressures predicted by the proposed method are in better agreement with the experimental results than the results by the other methods.  相似文献   

河北柳江盆地柳江村上石盒子组露头研究          下载免费PDF全文

刘梦瀛  胡光明  左宇  范一鸣  王旭阳 《沉积与特提斯地质》2018,38(4):104-110

目前资料对柳江盆地上石盒子组沉积特征的描述比较简略,针对这种情况,本团队详细考察了柳江村小北山露头,以期揭示上石盒子组更多的沉积特征。通过对3条剖面进行分层,并详细描述岩层的岩性特征和沉积构造,认为该露头发育有侧积体和典型的牛轭湖,为曲流河沉积体系。根据河相经验公式算出其弯曲度大于1. 7,为高弯度曲流河。在演化过程中,曲流河的规模逐渐变小,同时经历了频繁改道和迁移。此项研究对于实习教学和河流构型研究均有参考价值。  相似文献   

直角分水口水流形态的实验研究   总被引：4，自引：0，他引：4       下载免费PDF全文

罗福安  梁志勇 《水科学进展》1995,6(1):71-75

对分水口前水流形态进行了研究,测量了分水口前不同水深处的平面流场,初步给出了分水口前水流的运动形态,分析了分水宽度沿水深的变化规律。  相似文献   

武昌电离层E-F谷区白天变化形态   总被引：2，自引：0，他引：2       下载免费PDF全文

苏元智  黄信榆 《地球物理学报》1987,30(6):555-559

本文利用文献[4]的分析程序对武昌地区三年共300多张频高图作了剖面换算和统计分析,得出白天E-F谷区电离的基本形态并发现一些新的变化特征;对分析结果的可能原因提出了讨论。  相似文献   

Barchans of Minqin: Morphometry   总被引：2，自引：0，他引：2  

Zhen-Ting Wang  Shi-Chen Tao  Yao-Wen Xie  Guang-Hui Dong 《Geomorphology》2007,89(3-4):405-411

The barchans on the border of Minqin oasis, China, were surveyed. Our data reconfirmed that the height of slipface is proportional to the width of horns and the baseline can be roughly described by parts of an ellipse and a parabola. We attempted to study dune geomorphology using the theory of differential geometry. The geometrical characteristics of the brink can be quantitatively determined by its curvature and torsion.  相似文献