THE FORMATION AND DEVELOPMENT OF A MESOSCALE CONVECTIVE SYSTEM WITH HEAVY RAINFALL ALONG SOUTH CHINA COASTAL AREA   总被引：1，自引：1，他引：0  

蒙伟光  张艳霞  戴光丰  闫敬华 《热带气象学报(英文版)》2008,14(1):57-60

Observational analysis shows that a Mesoscale Convective System (MCS) occurred on May 13- 14 2004 along the coastal area in South China. The MCS initiated among the southwesterly flows within a west-east orientation low-level shear line. Associated with the system, in its subsequent development stages, no distinct vortex circulation developed in low-level. Instead, a cyclonic flow disturbance was observed in the mid-troposphere. How the convection starts to develop and evolve into a MCS? With observational analysis and numerical simulation, the problem has been studied. The high-resolution MM5 simulation shows that topographic convergence along the coastal line and the nearby mountains in western South China plays an important role to initiate the MCS convection. Once the convection occurs, due to the condensation heating, a cooperative interaction between the preexisting mid-level disturbance and convection is created,which may greatly affect the MCS development during periods when the system continues moving eastward.Compared to some typical MCS that happen in Southern China, which are usually accompanied with upward development of cyclonic vorticity, the development and evolution of the investigated MCS shows distinguishing features. In this article, the physical mechanisms responsible for the intensification of mid- level disturbance are discussed, and a viewpoint to interpret the effects of mid-level disturbance on the MCS organizational development is proposed.  相似文献   

地磁低点位移频谱特征及机理探讨   总被引：1，自引：0，他引：1       下载免费PDF全文

张学民  钱家栋  王亚丽  赵旭  欧阳新艳  赵庶凡 《地震学报》2008,30(5):474-483

以河北省昌黎地震台为例,使用该台地磁Z分量的分钟值数据,分别对比了正常时段、磁暴发生时段、 低点位移时段的主要频率谱值变化特征. 通过多频点功率谱对数拟合,发现在数据长度相等的情况下,相对于正常时段而言磁暴时段各频率的能量明显增强,特别是高频端尤其明显; 而当大范围低点位移发生时,高频端的能量基本与正常时段持平,但4个小时以上的周期功率谱大部分要低于正常段. 通过对多日低点位移时段的FFT累加与正常时段对比后发现,低点位移发生时,8.5小时和13.7小时周期的频谱值增加. 通过与DE-METER卫星观测的电子密度数据空间图象进行对比,发现地磁低点位移的发生与空间Ne的增加有很好的对应性. 最后对这些变化特征及低点位移可能产生的机制进行了探讨.   相似文献   

西伯利亚下地幔底部的剪切波各向异性   总被引：1，自引：0，他引：1       下载免费PDF全文

杨凤琴  刘斌  倪四道  曾祥方  戴志阳  吕彦 《地震学报》2008,30(2):209-213

D"在地球动力学演化中起着重要的作用.地震学研究已表明,D"区存在着显著的大尺度区域的地震波各向异性,但由于地震震源与接收台分布的地理局限性,D"区各向异性的研究主要局限于北太平洋、加勒比海、阿拉斯拉、中太平洋等地区(Wookey et al,2005;Garnero,Lay,2003;Matzel,1996;Pulliam,Sen,1998),对西伯利亚下地幔底部的各向异性研究目前尚未见到.  相似文献   

Geometric structure and formation mechanism of Lintong-Chang’an fault zone     

师亚芹  冯希杰  戴王强  李晓妮  任隽  种瑾 《地震学报(英文版)》2008,21(2):156-169

The results from investigation of large quantity of fault outcrops and artificial earthquakes suggest that the Lin-tong-Chang’an fault zone mainly consists of two faults. One is the Majie-Nianwan fault that separates a branch of Wangjiabian-Houjiawan fault on the right bank of the Bahe River; the other is the Hujiagou-Shoupazhang fault that separates a branch of Zhongdicun-Tangjiazhai fault in Tongrenyuan and Shaolingyuan. As tensional dip-slip normal faults, the faults distribute with approximately parallel equal intervals in local regions and the profiles drop in a step-like form to the northwest, presenting a Y-shape combination. The result from deep seismic reflection indicates that the fault is about 5~8 km in depth, which is not only a basement fault, but also a listric normal fault in the deep stratum. The Lintong-Chang’an fault is a typical outstretching rift system under the NS-trending ten-sion stress field. At the same time, affected by the sinistral strike slip of the Yuxia-Tieluzi fault, the fault extends like a broom from the northeast to the southwest.  相似文献   

甘肃年度地震危险区划定的R值评分研究     

代炜  胡永钧  孙军杰  冯建刚  陈立琼 《中国地震》2008,24(3)

年度地震危险区是一个比较特殊的评价对象.作者在前人研究的基础上对R值评分公式做了适当的改进,将原有方法的用地震个数求报准率,改为用地震危险区面积求取报准率,在不改变公式物理意义的前提下,使其更适合于对年度地震危险区这个特殊对象做出科学评价.改进后的公式排除了数学上不成立的情况,不鼓励虚测,不鼓励漏测.对甘肃1986～2007年的年度地震危险区和目前甘肃地震预测预报水平做出了科学客观的评价.依据评价结果提出了改进年度地震危险区划定方法的建议.  相似文献   

A comparative overview of weathering intensity and HCO₃ flux in the world's major rivers with emphasis on the Changjiang,Huanghe, Zhujiang (Pearl) and Mississippi Rivers     

Wei-Jun Cai  Xianghui Guo  Chen-Tung Arthur Chen  Minhan Dai  Longjun Zhang  Weidong Zhai  Steven E. Lohrenz  Kedong Yin  Paul J. Harrison  Yongchen Wang 《Continental Shelf Research》2008

In this paper, general relationships of riverine bicarbonate concentrations and fluxes as a function of drainage basin mineral content and runoff are examined using a database of the 25 largest rivers in the world. Specific HCO₃⁻ flux normalized to unit basin area, which peaks in the mid latitudes, was found to be strongly correlated with the carbonate mineral content of river basins, while river HCO₃⁻ concentration was related to the balance of precipitation and evaporation. Within this global context, the weathering patterns of CO₂ in a few large rivers (Changjiang, Huanghe, Pearl, and Mississippi rivers) were examined in further detail. The Zhujiang (Pearl River), especially its largest branch (Xijiang), was characterized by the highest specific weathering rate among all the world's large rivers due to an exceptionally high carbonate mineral content (over 80%) in its drainage basin and its warm and wet environment. It has a moderate level of HCO₃⁻ concentration, however, due to dilution by relatively high precipitation in the watershed. In stark contrast, the Huanghe (Yellow River) has one of the lowest specific weathering rates because of low carbonate mineral content and a dry climate. However, it has a high HCO₃⁻ concentration due largely to the concentrating effects of high evaporative water loss, as a result of arid weather and the agricultural use of water through irrigation systems, as well as carbonate-containing surficial deposits (i.e., loess). The strong correlation between specific HCO₃⁻ fluxes and discharge in all four rivers with different discharge seasonality suggests that higher precipitation in drainage basins promotes higher weathering rates.  相似文献   

CDMA VPDN构建IP数字测震台网     

谌亮  张艺  戴仕贵 《地震地磁观测与研究》2008,29(1):70-76

通过对目前CDMA2000 1x网络技术和构架的深入介绍,可了解CDMA VPDN的应用原理。针对CDMA传输的早期台网方案在应用中的不足,以四川省数字测震台网为例,详细介绍了利用CDMA VPDN构建IP数字测震台网的组网方式和网络构架。最后,对该方案使用中存在的一些常见问题给予了详细分析并针对问题提出了处理方法和建议。  相似文献   

青岛崂山ML 4．1地震序列应力降变化研究   总被引：1，自引：1，他引：0  

郑建常  潘元生  万连初  代磊 《地震地磁观测与研究》2008,29(4)

根据Andrews谱积分方法,采用近震源Brune圆盘模型,研究了2003年6月3日青岛崂山ML4.1地震序列破裂过程中应力降变化情况.结果表明,崂山序列主震静应力降为24 MPa,动态应力降大约为静态应力降的2.2倍;崂山序列余震应力降普遍低于5 MPa,约有80%的余震应力降小于1 MPa,显示出与主震断层面有关的余震低应力降现象,这说明主震的破裂与余震破裂过程之间存在明显的差别.这种现象与崂山序列的弱强度衰减一致,表明此次序列的余震属于低能量破裂过程.计算结果显示:①由Andrews谱积分方法得到的小震应力降与震级大小存在一定的相关性;②小应力降事件的静态应力降和动态应力降的比值普遍小于1,未发现明显的应力降之比与Brune应力降之间的关系.  相似文献   

三十烷醇对海带三个品系雌配子体克隆生长和发育的影响   总被引：4，自引：1，他引：3  

庄岩  戴继勋 《海洋湖沼通报》1998,(4):39-42

以海带雌配子休克隆为实验材料,通过施用三十烷醇处理。结果表明,三个品系在供试条件下,LH36生长最好,LH30发育率最高。它们对TA的反应为浓度在0．5～1．0×10-5mg／L时,都有促生长作用,其中LH30反应最敏感,LH10次之。浓度在1．0×10-5mg／L时,发育率最高,其中LH30发育率为51．5％,LH10为18．0％。LH36对各浓度处理的发育反应,差异都不明显。  相似文献   

利用WSBV的引物扩增中国对虾的杆状病毒DNA     

汪岷  苏冬梅  包振民  邵济钧  戴继勋 《中国海洋大学学报(自然科学版)》1998,(4)

利用台湾报道的ＷＳＢＶ的ＰＣＲ引物,成功地扩增出了１４００ｂｐ左右的中国对虾的杆状病毒的ＤＮＡ片段,与预计的产物长度吻合。该引物对经初步离心处理的病虾组织也能扩增出特异性ＤＮＡ条带,而对正常虾组织ＤＮＡ、昆虫杆状病毒（ＡｃＭＮＰＶ）ＤＮＡ进行扩增,均获得阴性结果。说明该引物的特异性较高,对中国对虾的杆状病毒的检测具有一定的实际应用价值。实验结果同时说明ＷＳＢＶ与中国对虾的杆状病毒有同源序列存在,具有一定的保守性;用该引物进行的ＰＣＲ扩增为中国对虾的杆状病毒与其他相关病毒的比较研究提供了一种技术手段。  相似文献