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阿尔金山北缘喀腊大湾地区早古生代中酸性侵入岩岩石地球化学特征及构造意义 总被引：1，自引：0，他引：1
喀腊大湾地区位于阿尔金山脉东北缘,当地早古生代时期构造环境复杂并且伴随剧烈的花岗质岩浆活动.通过对区域内早古生代中酸性侵入岩5个岩体（大平沟岩体、阿北银铅矿岩体、阿北岩体、4337北花岗岩体、喀腊大湾南岩体）的岩石学、岩相学、地球化学特征研究,探讨早古生代区域重大构造事件和构造环境.南部的喀腊大湾南岩体表现低钾性质,其余4个岩体样本为中高钾钙碱性中酸性岩,并且有向高钾演变的趋势,铝饱和指数在1.0~1.1之间,数据统计和分析大部分样品具有I型花岗岩特征,少部分显示了I型向S型过渡的性质,代表了洋壳-陆壳活动性大陆边缘的环境.结合喀腊大湾周边地质背景,本地区应该是阿尔金古洋壳和塔里木地块南北向碰撞作用的火山岛弧区域. 相似文献
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Parallel back-building convective lines are often observed extending to the southwest of some mesoscale convective systems(MCSs)embedded in the mei-yu front in China.The convective lines with echo training behavior can quickly develop into a stronger convective group of echoes,resulting in locally heavy rainfall within the mei-yu front rainband.The initiation mechanism of the back-building convective lines is still unclear and is studied based on high-resolution numerical simulation of a case that occurred during 27?28 June 2013.In the present case,the new convection along the convective lines was found to be forced by nonuniform interaction between the cold outflow associated with the mei-yu front MCSs and the warm southerly airflow on the south side of the mei-yu front,which both are modified by local terrain.The mei-yu front MCSs evolved from the western to the eastern side of a basin surrounded by several mesoscale mountains and induced cold outflow centered over the eastern part of the basin.The strong southwest airflow ahead of the mei-yu front passed the Nanling Mountains and impacted the cold outflow within the basin.The nonuniform interaction led to the first stage of parallel convective line formation,in which the low mountains along the boundary of the two airflows enhanced the heterogeneity of their interaction.Subsequently,the convective group quickly developed from the first stage convective lines resulted in apparent precipitation cooling that enhanced the cold outflow and made the cold outflow a sharp southward windshift.The enhanced cold outflow pushed the warm southerly airflow southward and impacted the mountains on the southeast side of the basin,where the roughly parallel mountain valleys or gaps play a controlling role in a second stage formation of parallel convective lines. 相似文献
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Assessment of shallow landslides from Hurricane Mitch in central America using a physically based model 总被引：5，自引：2，他引：3
Shallow landslides induced by heavy rainfall events represent one of the most disastrous hazards in mountainous regions because
of their high frequency and rapid mobility. Recent advancements in the availability and accessibility of remote sensing data,
including topography, land cover and precipitation products, allow landslide hazard assessment to be considered at larger
spatial scales. A theoretical framework for a landslide forecasting system was prototyped in this study using several remotely
sensed and surface parameters. The applied physical model SLope-Infiltration-Distributed Equilibrium (SLIDE) takes into account
some simplified hypotheses on water infiltration and defines a direct relation between factor of safety and the rainfall depth
on an infinite slope. This prototype model is applied to a case study in Honduras during Hurricane Mitch in 1998. Two study
areas were selected where a high density of shallow landslides occurred, covering approximately 1,200 km2. The results were quantitatively evaluated using landslide inventory data compiled by the United States Geological Survey
(USGS) following Hurricane Mitch’s landfall. The agreement between the SLIDE modeling results and landslide observations demonstrates
good predictive skill and suggests that this framework could serve as a potential tool for the future early landslide warning
systems. Results show that within the two study areas, the values of rates of successful estimation of slope failure locations
reached as high as 78 and 75%, while the error indices were 35 and 49%. Despite positive model performance, the SLIDE model
is limited by several assumptions including using general parameter calibration rather than in situ tests and neglecting geologic
information. Advantages and limitations of this physically based model are discussed with respect to future applications of
landslide assessment and prediction over large scales. 相似文献
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The Lechówka section comprises the most complete Cretaceous–Paleogene (K-Pg) boundary succession in Poland and is among 29 sites worldwide with the youngest ammonite record. Here, cephalopods (ammonites and nautilids), organic-walled dinoflagellates (dinocysts) and foraminifera from the uppermost Maastrichtian interval are studied. In terms of ammonite biostratigraphy, the upper Maastrichtian Hoploscaphites constrictus crassus Zone is documented up to a level 120 cm below the K-Pg boundary. There is no direct, ammonite-based evidence of the highest Maastrichtian H. constrictus johnjagti Zone. However, the predominance of the dinocyst marker taxon Palynodinium grallator suggests the presence of the equivalent of the uppermost Maastrichtian Thalassiphora pelagica Subzone, which is correlatable with the H. c. johnjagti ammonite Zone. The planktonic foraminiferal assemblage is coeval with that from the H. c. johnjagti Zone as well. These data indicate that the top of the Maastrichtian at Lechówka is complete within the limits of biostratigraphic resolution, albeit slightly condensed. The dinocyst and foraminiferal assemblages are dominated by taxa that are characteristic of high-energy, marginal marine environments. A reduction in test size among the calcareous epifaunal benthic foraminifera is observed at a level 50 cm below the K-Pg boundary, which is possibly related to environmental stress associated with Deccan volcanism. 相似文献
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We describe a small ilium, with fibrous texture characteristic of juvenile bone, from the lower Cenomanian of central Utah, U.S.A. The ilium was recovered from the upper part of the Mussentuchit Member of the Cedar Mountain Formation. The ilium most closely resembles that of immature ceratopsid ilia referred to Agujaceratops mariscalensis from the Campanian Aguja Formation of southern Texas, U.S.A. Both have everted dorsal margins over the iliac body, subhorizontal postacetabular processes, and laterally compressed, anteroventrally curved preacetabular processes. If correctly identified, the small ilium from the Cedar Mountain Formation is the oldest ceratopsid or ceratopsoid known, and shows that the diversity of early ceratopsians was greater than previously realized. 相似文献
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Dalia Bach Kirschbaum Robert Adler Yang Hong Stephanie Hill Arthur Lerner-Lam 《Natural Hazards》2010,52(3):561-575
A systematic inventory of landslide events over the globe is valuable for estimating human and economic losses, quantifying
the relationship between landslide occurrences and climate variations and for evaluating emerging global landslide prediction
efforts based on remote sensing data. This study compiles a landslide catalog for rainfall-triggered events for several years,
drawing upon news reports, scholarly articles, and other hazard databases to provide a landslide catalog at the global scale.
While this database may only represent a subset of rainfall-triggered landslides globally, due to lack of reports, it presents
a lower boundary on the number of events globally and provides initial insight into the spatiotemporal statistical trends
in landslide distribution and impact. This article develops a methodology for landslide event compilation that can be used
in evaluating global landslide forecasting initiatives and assessing patterns in landslide distribution and frequency worldwide. 相似文献
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多卫星遥感降水产品为无/缺资料地区的水文过程模拟提供了新的数据来源。结合地面高密度雨量站网,在中国典型暴雨区赣江流域定量评估两种TRMM降水产品(3B42V7和3B42RTV7)的精度,并通过耦合分布式水文模型CREST,探讨了水文模拟中TRMM卫星降水产品对地面观测降水的可替代性。研究表明:3B42和3B42RT与地面观测流域平均月降水相关系数达到0.9以上,偏差在5%以内,日尺度上相关性略差,偏差略有增加。同时设计2种水文模拟对比试验:情景I为静态参数,使用地面雨量站降水率定模型参数,采用卫星降雨验证模型;情景II为动态参数,采用卫星数据重新率定模型参数,再利用卫星降雨验证模型。对比结果表明:情景II中完全使用TRMM降水后模型效果明显改善,证明TRMM卫星数据在赣江流域具有替代地面站点观测的潜力,但需要重新根据卫星降雨率定模型。 相似文献
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Observing system simulation experiments are performed using an ensemble Kalman filter to investigate the impact of surface observations in addition to radar data on convective storm analysis and forecasting. A multi-scale procedure is used in which different covariance localization radii are used for radar and surface observations. When the radar is far enough away from the main storm so that the low level data coverage is poor, a clear positive impact of surface observations is achieved when the network spacing is 20?km or smaller. The impact of surface data increases quasi-linearly with decreasing surface network spacing until the spacing is close to the grid interval of the truth simulation. The impact of surface data is sustained or even amplified during subsequent forecasts when their impact on the analysis is significant. When microphysics-related model error is introduced, the impact of surface data is reduced but still evidently positive, and the impact also increases with network density. Through dynamic flow-dependent background error covariance, the surface observations not only correct near-surface errors, but also errors at the mid- and upper levels. State variables different from observed are also positively impacted by the observations in the analysis. 相似文献
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How to obtain fast-growth errors, which is comparable to the actual forecast growth error, is a crucial problem in ensemble forecast (EF). The method, Breeding of Growth Modes (BGM), which has been used to generate perturbations for medium-range EF at NCEP, simulates the development of fast-growth errors in the analysis cycle, and is a reasonable choice in capturing growing errors modes, especially for extreme weather by BGM. An ideal supercell storm, simulated by Weather Research Forecast model (WRF), occurred in central Oklahoma on 20 May 1977. This simulation was used to study the application of BGM methods in the meso-scale strong convective Ensemble Prediction System (EPS). We compared the forecasting skills of EPS by different pertubation methods, like Monte-Carlo and BGM. The results show that the ensemble average forecast based on Monte-Carlo with statistics meaning is superior to the single-deterministic prediction, but a less dynamic process of the method leads to a smaller spread than expected. The fast-growth errors of BGM are comparable to the actual short-range forecast error and a more appropriate ensemble spread. Considering evaluation indexes and scores, the forecast skills of EPS by BGM is higher than Monte-Carlo’s. Furthermore, various breeding cycles have different effects on precipitation and non-precipitation fields, confirmation of reasonable cycles need consider balance between variables. 相似文献