华南暖区暴雨研究进展   总被引：23，自引：8，他引：15       下载免费PDF全文

何立富  陈涛  孔期 《应用气象学报》2016,27(5):559-569

华南前汛期暴雨预报一直是我国大气科学界的一个研究热点,特别是发生在锋前的暖区暴雨,由于其天气尺度斜压性强迫不明显,环境大气水汽含量丰富,热动力不稳定性强,边界层触发机制复杂,以及特殊的地形和海陆热力差异的外强迫作用,导致暴雨突发性强,地域性特征显著,也是困扰预报业务人员的难点问题。目前我国预报业务中使用的全球数值预报模式对暖区暴雨的预报能力十分有限,高分辨率中尺度数值模式的预报效果也不尽人意。该文回顾了近40年华南前汛期暴雨大部分研究成果,针对华南暖区暴雨的提出及典型背景场、暖区暴雨与低空急流的关系、暖区中尺度对流系统的形成及传播、暖区暴雨触发机制等独特的天气动力学特征进行了系统梳理与分析,并依据前人研究成果及中央气象台预报实践经验,总结提炼了3类华南暖区暴雨类型——边界层辐合线型、偏南风风速辐合型,以及强西南急流型的天气系统配置及触发因子。最后提出针对华南暖区暴雨需要进一步研究的科学问题。  相似文献   

Characteristic and Geological Significance of Microbially Induced Sedimentary Structures(MISS) in Terrestrial P-T Boundary in Xingyang,Western He’nan Province     

Zheng Wei  Qi Yongan  Zhang Zhonghui  Xing Zhifeng 《地球科学进展》2016,31(7):737-750

Microbially Induced Sedimentary Structures (MISS) are primary sedimentary structures that arise syndepositionally from microbial community activity. Especially valuable are MISS for the analysis of early Archean (and extraterrestrial) deposits. However, most reports of MISS have focused on the Precambrian and Phanerozoic mass extinction marine sediments, and only a few and terrestrial MISS have been studied. The MISS presented in this paper, which mainly consists of mat growth feature, mat destruction feature and mat decay feature, are well preserved in terrestrial clastic rocks around the P-T boundary in Xiyang area, western Henan. Large U ridges, oriented sand quartz, mica grains and thin clayey laminae arranged parallel to bedding plane are the main features visible under the microscope. Several lines of evidence indicate that the Xingyang MISS are of biogenic origin. Abundant MISS in Xingyang may indicate the degradation of terrestrial ecosystems and proliferation of microbial mats immediately after the severe Permian-Triassic mass extinction. Study aiming at MISS helps to analyze their space distribution in the globe and to probe into links between microbial proliferation and environmental stresses following the end-Permian mass extinction in terrestrial ecosystems.  相似文献   

层状边坡滑动边界强度参数取值方法研究     

向俊博  喻邦江  刘士伟  魏玉峰  王小群 《地质灾害与环境保护》2016,(3):75-80

滑坡滑带土强度参数取值的准确性,决定了滑坡稳定性计算的可靠程度。因此获得准确、可靠的滑动边界强度参数至关重要。然而在实际情况中,由于取样位置试样的代表性,以及试样转运过程中保存条件的限制,现场所取得的滑带土在室内试验得到的强度参数已经不能完全反映真实环境下的抗剪强度。因此考虑软弱夹层、滑带土各种物理和力学指标间存在必然联系,并表现出特定的规律性,尝试通过试验,揭示指标间的关联规律,并建立了相关性好的关系式,据此评价滑动边界的抗剪强度参数。  相似文献   

锆石Hf和全岩Nd同位素填图研究进展:以三江特提斯造山带为例   总被引：5，自引：5，他引：0  

杜斌  王长明  贺昕宇  杨立飞  陈晶源  石康兴  罗政  夏锦胜 《岩石学报》2016,32(8):2555-2570

近年来,区域性的Nd-Hf同位素填图正成为探索岩石圈结构和演化,制约陆块边界位置和壳-幔相互作用以及它们与金属成矿作用耦合关系的重要研究方法。目前的研究主要集中于中国的拉萨地体以及澳大利亚太古宙尤冈克拉通,包括地体地壳性质与空间变化规律、成矿系统约束和区域找矿潜力等方面。本文以三江特提斯造山带为例,使用克里格插值法在MAPGIS平台完成同位素等值线图,基此解析三江地区岩石圈结构以及大规模成矿作用。Nd-Hf同位素填图支持昌宁-孟连缝合带为冈瓦纳和泛华夏古陆的分界。昌宁-孟连缝合带划分了两个εNd(t)同位素明显不同的异常区,缝合带以西表现为古老地壳基地组成,而缝合带以东部表现为较年轻的地体。三江特提斯造山带中不同类型与岩浆岩有关的发矿床大多汇聚在同位素边界处,这些同位素边界可能代表着地体边界或缝合带、岩浆弧。沿金沙江-哀牢山缝合带分布的斑岩型或斑岩-矽卡岩型Cu-(Mo)矿床,具有高εHf(t)正值和较高εNd(t)负值的特征,对应始新世钾质斑岩及有关的矿化。在腾冲-保山地块、义敦岛弧和临沧次地块,具有低εHf(t),低εNd(t)值岩浆岩分布特征,主要形成与过铝质花岗岩型有关的锡-钨矿床。因此,我们认为区域尺度的同位素填图对研究岩石圈结构和演化、解剖壳-幔相互作用机理、解析深部动力学机制和成矿机制、总结区域成矿规律和指导区域成矿潜力具有重要意义。  相似文献   

高阶边界元方法求解规则波在三维局部渗透海床上的传播     

章旭  勾莹  倪云林  滕斌  刘珍 《海洋学报》2016,38(1):133-142

基于线性势流理论,利用高阶边界元法研究了规则波在三维局部渗透海床上的传播。根据Darcy渗透定律推导出渗透海床的控制方程,利用渗透海床顶部和海底处法向速度和压强连续条件得到渗透海床顶部满足的边界条件。根据绕射理论,利用满足自由水面条件的格林函数建立了求解渗透海床绕射势的边界积分方程,采用高阶边界元方法求解边界积分方程进而得到自由水面的绕射势和波浪在局部渗透海床上传播过程中幅值的变化情况。通过与已发表的波浪对圆柱形暗礁的时域全绕射结果对比,证明了本文建立的频域方法计算波幅的正确性和有效性。利用这一模型研究了三维矩形渗透海床区域上波浪的传播特性,并分析了入射波波长、海床渗透特性系数等参数对波浪传播的影响。  相似文献   

Calculation method for thickness of discontinuous boundary layer of engineering pavement     

ZhongQiong Zhang  QingBai Wu  Peng Zhang  SiRu Gao 《寒旱区科学》2016,8(6):461-466

The boundary layer is a buffer layer of water and heat exchange between the atmosphere and permafrost.Based on the atmospheric boundary layer and heat transfer theory,we established a method for determining the boundary layer thickness of engineering pavement(asphalt and sand pavement)in permafrost region.The boundary layer can be divided into the Boundary Layer Above Surface(BLAS)and the Boundary Layer Below Surface(BLBS).From in-situ monitoring data,the thickness of BLAS was determined through the laminar thickness,and the thickness of BLBS was determined through ground temperature,the heat conduction function,and the mean attenuation function(α).For asphalt pavement,the BLAS thickness varied between 2.90 and 4.31 mm and that of BLBS varied between 28.00 and 45.38 cm.For sand pavement,the BLAS thickness varied between 2.55 and 3.29 mm and that of BLBS varied between 15.00 and 46.44 cm.The thickness varied with freezing and thawing processes.The boundary layer calculation method described in this paper can provide a relatively stable boundary for temperature field analysis.  相似文献   

矿业权边界在资源储量估算垂直纵投影图上的确定   总被引：1，自引：0，他引：1       下载免费PDF全文

贾绍松  栾元滇  岳伟佳  杨元 《山东国土资源》2016,32(1)

利用垂直纵投影图进行资源储量估算时,当矿体走向与矿业权边界斜交时,矿业权边界在资源储量垂直纵投影图上投影的准确位置较难确定。该文介绍了利用不同中段平面图和利用计算公式确定矿业权边界在资源储量垂直纵投影图上的投影位置,对解决此类问题具有一定的参考价值。  相似文献   

Tracking temporal palynofloral changes close to Cretaceous-Paleogene boundary in Deccan volcanic associated sediments of eastern part of central Deccan volcanic province     

《世界地质(英文版)》2016,(4):205-215

Deccan volcanic sequences( DVS) in the central Deccan volcanic province( CDVP) are designated as Sahyadri Group having ~ 500 m thick lava pile associated with multiple sedimentary beds at different stratigraphic levels. In the eastern part of CDVP between the latitude 19 °55 '--20 °25 ' N and the longitudes 78 °15 '--78 °30 ' E,palynological investigation of the intertrappean sedimentary beds at five stratigraphic levels was carried out. The study was basically aimed for tracking the floral and environmental changes across the Deccan transition. The resulting finds indicate that the intertrappean sediments at the lowest stratigraphic level between the earliest lava flows are characterized by presence of marker Maastrichtian palynomorphs- Gabonisporis vigourouxii,Aquilapollenites bengalensis,Azolla cretacea and Farabeipollis associated with triporate and tricolpate pollen grains,phytoliths of Oryzeae of Poaceae family and peridinoid dinoflagellate cysts. The increasing volcanism deteriorated the existing flora as evident by absence of pollen-spores and presence of only structured biodegraded organic matter,fungal spores,acritarchs and algal( Botryococcus) remains in the sediments of higher-up in the sequence. For chronostratigraphic constraints on the lava flows magnetic polarity of the flows bracketing the intertrappean beds was investigated. The results indicated presence of N-R-N-R magnetic polarity in the basal lava pile that are interpreted as representing the magnetochron C30 N to C28 R( Maastrichtian-Paleogene). The floral change begins with the onset of volcanism in the chron C30 N and floral deterioration is observed in C29 N with increasing volcanism and it is only in the chron C28 R( Danian) that some evidence of recovery of flora is recorded. The current study shows that in eastern part of CDVP the post Cretaceous-Paleogene boundary eruptions represent the main phase of eruptions that triggered deterioration of the flora.  相似文献   

TTI介质拟声波方程数值模拟     

黄杰  杨国权  李振春  谷丙洛 《物探与化探》2018,(1):134-143

TTI介质qP波数值模拟方法因为考虑了倾角因素,可以比VTI介质qP波数值模拟方法更加准确地描述各向异性介质中地震波场的传播规律。文中用拟声波方程对TTI介质中的地震波场进行了高阶有限差分数值模拟,在改进衰减函数分布方式后,通过坐标变换,利用改进的完全匹配层(perfectly matched layer,PML)边界控制方程对波场边界进行吸收处理,取得了良好的效果;然后分析了拟声波方程数值模拟中的稳定性问题,并对波场中的伪横波进行压制。通过对不同模型的数值模拟,验证了文中使用的TTI介质拟声波波动方程的稳定性以及所采用的PML边界控制方程的可靠性和适用性。  相似文献   

四川江油马角坝刺林包剖面二叠-三叠系间粘土岩研究     

邓煜霖  郎兴海  崔志伟  王旭辉  娄渝明  韩鹏 《岩石矿物学杂志》2018,37(3):417-433

二叠-三叠纪之交华南地区普遍发育火山成因的粘土岩,其对于了解二叠纪末大规模火山活动及扬子板块碎屑物质来源具有重要意义。本文对扬子西缘马角坝刺林包剖面飞仙关组底部粘土岩进行了碎屑锆石U-Pb定年及原位Hf同位素测试、X衍射和全岩地球化学分析,以揭示粘土岩的岩石成分及物源信息。镜下特征、X衍射及主量元素特征表明岩石中粘土矿物主要为伊利石,含少量方解石、石英。碎屑锆石年龄显示,特征峰值年龄主要集中在2 615~2 383、1 868~1 328、1 186~778和430~246 Ma,并出现~250 Ma特征高峰,结合原位Hf同位素特征表明锆石与秦岭造山带、华南典型PTB剖面粘土岩及峨眉山大火成岩省具有较高的相似性。同时,通过微量、稀土元素分析发现粘土岩中Zr、Hf、Th、Cr、Co、Ti相对富集,与华南典型PTB粘土岩和峨眉山玄武岩相近,并结合构造背景及锆石特征,综合认为刺林包剖面PTB粘土岩来自于秦岭造山带及龙门山岛链局部剥蚀区、二叠纪末火山活动和峨眉山大火成岩省剥蚀岩体。  相似文献