Monsoonal precipitation variation in the East Asia since A.D. 1840 ——Tree-ring evidences from China and Korea     

刘禹  Won-Kyu Park  蔡秋芳  Jung-Wook Seo  Hyun-Sook Jung 《中国科学D辑(英文版)》2003,46(10)

The main characteristic of the East Asian climate is the monsoon system. Plenty of studies have demonstrated that the Asian monsoon system plays a crucial role in the global climate sys- tem [1-4]. The Asian summer monsoon can be divided into two parts, t…  相似文献   

辽河盆地东部凹陷热历史及构造—热演化特征   总被引：9，自引：5，他引：9  

王永新  汪集旸  胡圣标 《地质科学》2003,38(2):214-220

根据辽河盆地东部凹陷大地热流测量和镜质体反射率数据,恢复了该区的热历史,结果表明:东部凹陷热流呈现古热流高现今热流低的变化特征,沙河街组三段沉积期到东营组沉积期(距今43～25Ma)盆地热流为66～82mWm²,现今热流值为47～70mWm²。构造沉降史分析显示,盆地经历了早期的裂谷阶段(距今43～25Ma)和后期的热沉降阶段,裂谷阶段包含了两个裂谷亚旋回。盆地现今较低的大地热流和较高的古热流及典型的裂谷型构造沉降样式为东部凹陷的构造—热演化提供了重要认识。  相似文献   

Stochastic Structural Modeling   总被引：3，自引：0，他引：3  

Lars Holden  Petter Mostad  Bjørn Fredrik Nielsen  Jon Gjerde  Chris Townsend  Signe Ottesen 《Mathematical Geology》2003,35(8):899-914

A consistent stochastic model for faults and horizons is described. The faults are represented as a parametric invertible deformation operator. The faults may truncate each other. The horizons are modeled as correlated Gaussian fields and are represented in a grid. Petrophysical variables may be modeled in a reservoir before faulting in order to describe the juxtaposition effect of the faulting. It is possible to condition the realization on petrophysics, horizons, and fault plane observations in wells in addition to seismic data. The transmissibility in the fault plane may also be included in the model. Four different methods to integrate the fault and horizon models in a common model is described. The method is illustrated on an example from a real petroleum field with 18 interpreted faults that are handled stochastically.  相似文献   

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   

Global thermal and dynamical perturbations due to Cretaceous mantle avalanche     

Philippe Machetel 《Comptes Rendus Geoscience》2003,335(1):91-97

The numerical models of mantle convection agree to depict avalanches behaviour according to the level of endothermicity of the spinel → perovskite phase change. Their potential effects on the global thermal and dynamical states of the mantle have been computed thanks to a numerical code, which takes into account both the 400-km exothermic and the 660-km endothermic phase changes. The cycle followed by the avalanches is: local layering, destabilization of the 660-km thermal layer, travelling and spreading on the core, and reappearing of the local layering. Therefore, mantle convection is characterized by quiet periods of partial layering embedded in catastrophic events. During the avalanche, the amplitude of the surface velocity is multiplied by two, which would imply an enhanced plate tectonic and ridge activities. The global thermal effects of the avalanche are compatible with a high mantle temperature and an acceleration of Earth's rotation during the Cretaceous. They also offer a coherent explanation to locate the origin of mantle plumes both within the CMB and just below the transition zone.  相似文献   

20世纪80～90年代我国气候增暖进程的统计事实   总被引：44，自引：8，他引：44       下载免费PDF全文

魏凤英  王丽萍等 《应用气象学报》2003,14(1):79-86

运用统计诊断方法分析了近50年来我国年平均及四季的气温变化特征，重点研究了20世纪90年代和80年代气温变化的主要差异及其增暖进程。结果表明，我国年平均气温是呈上升趋势的，但80年代以前年代际变化并不明显, 升温幅度不大。我国气候增暖始于20世纪80年代后期，90年代增暖加速，急剧增暖的主要原因是长江流域以南地区经历了由偏冷向偏暖的趋势转变。我国四季气温变化趋势在80～90年代增暖的进程中存在明显差异:其中冬季增暖开始时间最早、幅度最大、持续时间最长；90年代我国气候增暖急剧加速，其原因除了冬季气温持续攀升作用外，春、夏、秋季气温上升, 特别是春、夏季增暖幅度的加大增暖区域的显著扩展也起到很重要的作用。  相似文献   

陕南2002-06-08暴雨洪水灾害分析   总被引：5，自引：0，他引：5       下载免费PDF全文

孙伟  侯明全 《山西气象》2003,(1):29-31

利用太原市1961年至2000年气温和降水资料，以1971年至2000年各要素的平均值作为基本气候态，统计分析近40a来的气候变化情况，结果表明：40a来太原市气温呈非连续的增温趋势，平川上升率为0．273℃／10a，山区上升率为0．266℃／10a；降水量呈减少趋势，平川减少率为38．07mm/10a，山区减少率为20．75mm/10a。气候变化具有明显的阶段性、突变性和时空不对称性特征。  相似文献   

基于正交投影和广义投影(POCS)算法的研究进展     

姜明  张兆田 《CT理论与应用研究》2003,12(1):51-55

目的 在于提请有关读者关注近年来关于图像重建的凸集投影算法的进展，这一重要的方法及应用。方法 主要讨论了基于正交投影和广义投影的算法。对基于正交投影的算法，并讨论了一般形式的加权松驰格式，这包含了分块格式和同时格式。并以三个定理报道有关的算法收敛性结果。结果 分别包含了相容和不相容条件和弱强收敛下的结果。对基于广义投影的算法，有关的基本概念和例子，基本算法的收敛性结果。结论 报道最近关于引入松弛系数的工作和在CT图像重建中的应用。  相似文献   

江西2003年夏季罕见高温气候特征及成因分析   总被引：2，自引：2，他引：2  

尹洁  张传江  张超美  文绮新 《气象与减灾研究》2003,26(4):19-22

对江西省2003年夏季罕见高温干旱的强度、气候历史地位、500hPa环流形势特征和海温特征等进行了分析。结果表明,2003年夏季高温强度在多项指标上均排建国以来第一位;在500hPa环流形势上具有特殊的分布特征;在前期环流形势场和海温场上具有一些前兆特征,有较好的预报意义。  相似文献   

强震前大气层中温压相关特征的异常显示     

张慧  张苏平 《高原地震》1997,(3)

对中国大陆已发生的多次7级以上强震震中区气温、气压资料进行了研究，结果表明：在大震前（30天之内），气温－气压函数的平衡状态被破坏，其相关系数（代数值）不断增大，“正弓”形可作为短临异常的标志，同时对其成因也进行了初步探讨。  相似文献