月尺度降水可预报性的实验研究     

薛德强  奚秀芬 《山东气象》2000,20(3):14-17

利用信噪方差比探讨了山东省月尺度降水可预报性,发现２～３月、９～１０月不可预报,其它月份可预报性强。一般大气环流系统冬夏转换季节可预报性差。与１３个代表站预报评分进行了比较,发现可预报性指数越高,则实际预报评分也相对较高,两者有较好的对应关系。  相似文献   

Quantifying the effects of environmental change on an oyster population: A modeling study     

Margaret M. Dekshenieks  Eileen E. Hofmann  John M. Klinck  Eric N. Powell 《Estuaries and Coasts》2000,23(5):593-610

Three models are combined to investigate the effects of changes in environmental conditions on the population structure of the Eastern oyster,Crassostrea virginica. The first model, a time-dependent model of the oyster population as described in Powell et al. (1992, 1994, 1995a,b, 1996, 1997) and Hofmann et al. (1992, 1994, 1995), tracks the distribution, development, spawning, and mortality of sessile oyster populations. The second model, a time-dependent larval growth model as described in Dekshenieks et al. (1993), simulates larval growth and mortality. The final model, a finite element hydrodynamic model, simulates the circulation in Galveston Bay, Texas. The coupled post-settlement-larval model (the oyster model) runs within the finite element grid at locations that include known oyster reef habitats. The oyster model was first forced with 5 yr of mean environmental conditions to provide a reference simulation for Galveston Bay. Additional simulations considered the effects of long-term increases and decreases in freshwater inflow and temperature, as well as decreases in food concentration and total seston on Galveston Bay oyster populations. In general, the simulations show that salinity is the primary environmental factor controling the spatial extent of oyster distribution within the estuary. Results also indicate a need to consider all environmental factors when attempting to predict the response of oyster populations; it is the superposition of a combination of these factors that determines the state of the population. The results from this study allow predictions to be made concerning the effects of environmental change on the status of oyster populations, both within Galveston Bay and within other estuarine systems supporting oyster populations.  相似文献   

吐哈盆地及邻区早二叠世沉积特征与构造发育的耦合关系   总被引：7，自引：0，他引：7  

朱文斌  马瑞士  郭继春  孙岩  郭令智  徐鸣洁  胡德昭 《高校地质学报》2002,8(2):160-168

通过对不同露头剖面和探井资料的分析,在吐哈盆地及邻区区分出三种不同类型沉积相：（1）裂谷型海相火山喷发沉积相;（2）裂谷型陆相火山喷发沉积相;（3）造山带磨拉石相;不同沉积相特征并结合构造分析认为,早二叠世在吐哈及邻区存在二种不同类型的盆地,即前陆盆地和裂谷盆地,同时,还探讨了大陆一大陆碰撞带上两种不同类型盆地的形成机理。  相似文献   

北票—义县地区义县组岩石地层特征   总被引：6，自引：0，他引：6  

张立东  郭胜哲  张长捷  彭艳东  贾斌  陈树旺  邢德和  丁秋红  郑月娟 《地质与资源》2004,13(2):65-74

北票-义县地区的义县组地层是一套火山-沉积地层,其中火山岩地层占80%以上,具有四个火山作用亚旋回,第一亚旋回以基性-偏碱的基性-中基性火山作用为特征,第二亚旋回以中基性-酸性的火山作用为特征,第三亚旋回以基性-中性火山作用为特征,第四亚旋回以中酸性火山作用为特征;义县组火山-沉积地层包含至少7个沉积夹层,可以进一步归纳为四套沉积层,即底砾岩层、下部火山岩中的沉积夹层、中部湖相沉积层和上部河湖相沉积层,沉积层中生物化石主要集中在3个主要层位.综合火山岩的旋回性特征,岩石组合、岩石产出特征,不同岩石组合的上、下接触关系和岩石形成环境的分析结果,结合同位素年代学及生物地层学的研究成果,区内义县组被划分成了4个岩性段.同位素年龄数据显示义县组时代为早白垩世,其形成年龄介于135~120Ma之间,含中华龙鸟、孔子鸟和辽宁古果等珍稀化石的湖相沉积层是在125~127Ma之间形成的.  相似文献   

春季一次特殊的暴雨天气过程分析     

陈德林  梁利 《气象研究与应用》2000,21(3):19-21

对2000年春季一次高空槽快速移动影响的暴雨天气过程发生的特殊性进行分析,寻找这次暴雨过程发生的前期特征.  相似文献   

重庆地区夏季降水时空分布特征分析     

刘德  李永华 《高原山地气象研究》2000,20(4)

采用车贝雪夫正交多项式分解方法展开重庆地区夏季降水场, 揭示了最近40年来重庆地区夏季降水时空分布特征.研究结果表明:大部分年份重庆各地夏季降水变化趋势一致; 近40年来重庆地区夏季降水80年代中期以前有增加趋势,而80年代后期至今则有减少趋势, 洪涝灾害主要集中发生在80年代,70年代干旱姓频繁,从80年代末期开始至今,重庆地区又进入了一个干旱的相对高发期.  相似文献   

Adakitic lavas in the Central Luzon back‐arc region,Philippines: lower crust partial melting products?   总被引：6，自引：0，他引：6  

Graciano P. Yumul JR    Carla Dimalanta  Herve Bellon  Decibel V. Faustino  Joel V. De Jesus  Rodolfo A. Tamayo  JR    Ferdinand T. Jumawan 《Island Arc》2000,9(4):499-512

Abstract Volcanism in the back-arc side region of Central Luzon, Philippines, with respect to the Manila Trench is characterized by fewer and smaller volume volcanic centers compared to the adjacent forearc side-main volcanic arc igneous rocks. The back-arc side volcanic rocks which include basalts, basaltic andesites, andesites and dacites also contain more hydrous minerals (ie, hornblende and biotite). Adakite-like geochemical characteristics of these back-arc lavas, including elevated Sr, depleted heavy rare earth elements and high Sr/Y ratios, are unlikely to have formed by slab melting, be related to incipient subduction, slab window magmatism or plagioclase accumulation. Field and geochemical evidence show that these adakitic lavas were most probably formed by the partial melting of a garnet-bearing amphibolitic lower crust. Adakitic lavas are not necessarily arc–trench gap region slab melts.  相似文献   

The 1997 Umbria-Marche (Italy) earthquake sequence: analysis of the data recorded by the local and temporary networks   总被引：1，自引：0，他引：1  

M. Cattaneo  P. Augliera  G. De Luca  A. Gorini  A. Govoni  S. Marcucci  A. Michelini  G. Monachesi  D. Spallarossa  L. Trojani  Xgums 《Journal of Seismology》2000,4(4):401-414

We present some preliminary results obtained from thejoined analysis of the data collected by the permanentand the temporary networks operating in the area ofthe earthquake sequence that followed (andanticipated) the 26 September, Central Italy, mainshocks. In particular, these earthquake data haveallowed us to determine a well constrainedwave-velocity model (both P and S) with stationcorrections which demonstrated to produce robusthypocentral locations. These velocity modelswith station corrections have been used forre-locating the whole September 1997–July 1998subset of data of the permanent network, and theprevious background seismicity, starting from May1996. The focal mechanisms of the largest events werealso obtained from an analysis of the first-motionpolarities.Our results indicate that 1) the seismic activityaligns on a SE-NW trend for a total length of about50 km of extension; 2) the focal depth of theseevents is restricted to the range 0–9 km; 3) mostevents can be related to sub-parallel SW dipping faultplanes; 4) focal mechanisms of the largest shocks(M_L > 4) show a coherent behaviour, withnormal fault solution on SSE-NNW striking, SW dippingplanes; 5) the space-time evolution of the activitydisplays a discontinuous mode of energy release, withdifferent episodes of activation and an apparentclustering of aftershocks at the edges of the areaswhich presumably ruptured in the main shocks.  相似文献   

中国东部中新生代裂陷盆地与伸展山岭耦合机制   总被引：65，自引：5，他引：60  

刘和甫 《地学前缘》2000,7(4):477-486

中国东部中、新生代伸展构造系包括由松辽盆地、华北盆地和江汉盆地等构成的裂陷盆地 ,以及由大兴安岭、太行山及雪峰山等构成的伸展山岭。从大陆裂解和伸展构造动力学来看 ,主要存在底侵作用、对流作用和拆层作用 3种机制。因此裂陷盆地与伸展山岭耦合关系主要是深部壳幔作用在浅层的响应。  相似文献   

计算流体地球化学研究的进展   总被引：3，自引：0，他引：3  

张德会 《地学前缘》2000,(Z2)

成矿作用的化学机理可以通过实验和计算机模拟进行研究。随着计算机运算能力的不断增强 ,在地球化学中正在形成一门新兴学科———计算地球化学。其中热质输运模拟、化学质量迁移数值模拟和流体输运化学反应耦合动力学研究取得了显著进展。建立在Darcy定律和守恒方程基础上的多孔介质热质输运模拟通过流函数图、等温线图及速率矢量图等 ,从古水文学和流体地球化学方面高度动态研究成矿作用。根据化学和热力学原理进行的化学质量迁移数值模拟则通过矿物和流体中化学物种的热力学数据 ,预测多组分体系中发生的流体岩石相互作用 ,定量揭示经历了复杂化学反应进程的成矿作用的化学行为。将上述两方面结合的流体输运化学反应耦合动力学 ,可以从时间和空间上模拟真实成矿流体系统复杂的动力学行为 ,是计算流体地球化学的发展方向。  相似文献