厦门地区1995年6月8—9日大暴雨天气成因分析     

郭林  范新强 《台湾海峡》1997,16(1):17-20

１９９５年６月８￣９日闽南局部地区大暴雨主要是受南侵的冷空气和９５０２号热带风暴的共同影响而产生。该冷空气来源于整个西北地区和青藏高原东部，范围较大，由于受云贵高原地形的影响，槽在东移过程中表现出如下特点：大槽发生倾斜、断裂，然后又在沿海地区合并；大槽的结构特征为垂直方向同相位；在华南形成中尺度热带云团随西南气流北上影响闽南地区。与此同时，９５０２号热带风暴穿过台湾海峡与槽前云系相互作用。上述原因  相似文献   

竖直螺旋槽管强化传热传质特性的研究—壁面几何形状对液膜流动特性的影响     

梅宁  张则荣  陆建辉  石湘 《中国海洋大学学报(自然科学版)》2002,32(1):120-126

该文研究竖直螺旋槽管壁面液膜形成及流动特性。建立了单组分流体的物理和数学模型并得出解析解 ,并分析了壁面几何形状对液膜流动特性的影响。结果表明 :液膜的形状主要受表面张力影响 ,在表面内弯处液膜较厚 ,而在槽道起始部液膜较薄。相对于光滑直管 ,竖直螺旋槽管壁面液膜具有均匀的厚度分布和更好的传热传质性质。  相似文献   

A real-time observation network of ocean-bottom-seismometers deployed at the Sagami trough subduction zone,central Japan     

Eguchi  Takao  Fujinawa  Yukio  Fujita  Eisuke  Iwasaki  Sin-Iti  Watabe  Isao  Fujiwara  Hiroyuki 《Marine Geophysical Researches》1998,20(2):73-94

We installed a real-time operating regional observation network of Ocean-Bottom-Seismometers, connected to an electro-optical fiber communication cable, at the Sagami trough subduction zone, just south of the Tokyo metropolitan area, central Japan. The network, called ETMC, has six seismic observation sites at approximately 20 km spacing. In addition, there are three tsunami observation sites along the ETMC network to monitor the propagation process of tsunamis around the Sagami trough region.The on-line data from the ETMC has been improving the detection capability of smaller-magnitude earthquakes even at areas close to the margin of the trough. The ETMC data analyzing system, which has a function of real-time digital filtering for each seismic channel, can read the arrival times of P- and S-waves precisely, constraining well the automatic on-line hypocenter locations. The network has been providing useful information regarding the bending and downgoing process of the Philippine sea plate at the Sagami trough subduction zone.The pressure sensors of the installed network have a detection capability of tsunami wave trains with an amplitude of less than 1 cm. For example, the sensors recorded the full time history of tsunami wave trains, with mm order resolution, originating from a tsunami earthquake with 5.7 M_W and the tsunami magnitude of 7.5 occurred near Tori Shima (Tori Is.) of the Izu-Bonin Is. arc on September 4, 1996. The maximum amplitude of the tsunami signals on the trough-floor was approximately 1 cm (P-P), in contrast with approximately 20 cm (0-P) at a coastal site on Izu-Oshima, near the trough. Also, the pressure sensors observed tsunamis due to a large tsunami earthquake (7.1 M_W) at the northern New Guinea, on July 17, 1998.  相似文献   

Influence of slow active faults in probabilistic seismic hazard assessment: the northwestern margin of the València trough     

Hector Perea  Kuvvet Atakan 《Natural Hazards》2007,43(3):379-396

Areas of low strain rate are typically characterized by low to moderate seismicity. The earthquake catalogs for these regions do not usually include large earthquakes because of their long recurrence periods. In cases where the recurrence period of large earthquakes is much longer than the catalog time span, probabilistic seismic hazard is underestimated. The information provided by geological and paleo-seismological studies can potentially improve seismic hazard estimation through renewal models, which assume characteristic earthquakes. In this work, we compare the differences produced when active faults in the northwestern margin of the València trough are introduced in hazard analysis. The differences between the models demonstrate that the introduction of faults in zones characterized by low seismic activity can give rise to significant changes in the hazard values and location. The earthquake and fault seismic parameters (recurrence interval, segmentation or fault length that controls the maximum magnitude earthquake and time elapsed since the last event or T_e) were studied to ascertain their effect on the final hazard results. The most critical parameter is the recurrence interval, where shorter recurrences produce higher hazard values. The next most important parameter is the fault segmentation. Higher hazard values are obtained when the fault has segments capable of producing big earthquakes. Finally, the least critical parameter is the time elapsed since the last event (T_e), when longer T_e produces higher hazard values.  相似文献   

Geochemical characteristics of sediment pore water from Site XS-01 in the Xisha trough of South China Sea and their significance for gas hydrate occurrence     

Yang Tao  Jiang Shaoyong  Ge Lu  Yang Jinghong  Ling Hongfei  Wu Nengyou  Zhang Guangxue  Liu Jian  Chen Daohua 《Frontiers of Earth Science》2007,1(2):212-217

Gas hydrate is a recently-found new source of energy that mostly exists in marine sediments. In recent years, we have conducted gas hydrate exploration in the South China Sea. The Xisha trough, one of the promising target areas for gas hydrate, is located in the northern margin of the South China Sea, adjacent to several large oil and gas fields. The Xisha trough extends 420 km long with the water depth of 1 500 m in the west part and 3 400 m in the east part and deposits thick sediments with organic matter content of 0.41%–1.02%. Previous studies on topographical features, geological P-T conditions, structural geology, sedimentary geology and geophysical bottom simulating reflectors (BSR) in the Xisha trough suggest that this area is favorable for the formation and accumulation of gas hydrate. In this paper, we present geochemical analyses for the sediment and pore water from a piston core at Site XS-01 in the Xisha trough. Seven pore water samples were analyzed for their anion (Cl⁻, SO₄ ²⁻, Br⁻, I⁻) contents, cation (Na, K, Ca, Mg) contents and trace element (Li, B, Sr, Ba, Rb, Mn) contents. Eight sediment samples were analyzed for stable carbon and oxygen isotopic compositions. A number of geochemical anomalies such as anions (e.g. Cl⁻, SO₄ ²⁻), cations (e.g. Ca, Mg) and trace elements (e.g. Sr, Ba, B) were found in this study. For example, the concentrations of Cl⁻ and SO₄ ²⁻ in pore water show a decreasing trend with depth. The estimated sulfate/methane interface (SMI) is only 18 m, which is quite similar to the SMI value of 23 m in the ODP164 Leg 997 at Blake Ridge. The Ca, Mg and Sr concentrations of pore water also decrease with depth, but concentrations of Ba, and Mg/Ca and Sr/Ca ratios increase with depth. These geochemical anomalies are quite similar to those found in gas hydrate locations in the world such as the Blake Ridge and may be related to the formation and dissociation of gas hydrates. The salt exclusion effect during the gas hydrate formation will cause an increase in major ion concentrations in the pore waters that diffused upward such as Cl. The anaerobic methane oxidation (AMO) may lead to the change of SO₄ ²⁻ and other cations such as Ca, Mg, Sr and Ba in pore water. Low δ ¹³C value of authigenic carbonates is a good indicator for gas hydrate occurrence. However, the bulk sediment samples we analyzed all show normal δ ¹³C values similar to biogenic marine carbonates, and this may also suggest that no gas hydrate-related authigenic carbonates exist or their amount is so small that they are not detectable by using this bulk analytical method. In conclusion, we suggest that the Site XS-01 in the Xisha trough of the northern margin of the South China Sea is a potential target for further gas hydrate exploration. Translated from Quaternary Sciences, 2006, 26(3): 442–448 [译自: 第四纪研究]  相似文献   

用于检测同相轴的Duffing型系统恢复力项的讨论   总被引：1，自引：2，他引：1       下载免费PDF全文

赵雪平  李月  杨宝俊 《地球物理学进展》2006,21(1):53-60

在用于检测同相轴的Duffing型系统中，非线性恢复力项的选取至关重要．针对具有不同非线性恢复力项的混沌系统，本文首先就非线性恢复力项的来源进行了说明，然后通过对哈密顿系统和耗散系统的仿真实验分析，以及理论推导，确定了势能—哈密顿多项式方程中可用于混沌振子检测系统的各项幂次和各项系数组合关系，即非线性恢复力项的选取规则：幂次最高项为奇次，其系数大于零．  相似文献   

T213模式对强冷空气短期预报能力的分析检验   总被引：7，自引：1，他引：7  

张守峰  郭文华  张金艳  杨克明 《气象》2003,29(8):43-47

利用T213模式的500hPa高度、地面气压、850hPa温度预报格点资料和客观分析实况格点资料，对2001—2002年冬半年我国出现的8次强冷空气天气过程的主要影响天气系统进行了预报能力的客观分析检验。所得结果有利于数值预报产品的释用及实时预报业务。  相似文献   

浙江省北部地区一次飑线天气过程分析          下载免费PDF全文

王雷 张伟红林伟  王志武 《气象科技》2003,31(2):97-100

文章分析了2002年7月16日浙江省北部地区的一次飑线天气过程。分析表明：高空前倾槽是这次飑线发生的大尺度环流背景，飑线发生在副热带高压边缘的不稳定区域。浙江省北部地区低层暖湿平流和地面的持续强烈升温，一方面为其积蓄了大量不稳定能量；另一方面高空冷平流形成并大大促进了这一地区的不稳定层结，这一不稳定层结主要是通过高空、地面的温度差动平流来实现的。水汽分析表明：低层850hPa的水汽输送是通过暖湿西南气流来实现的，强对流发生的浙江省北部地区正好处于低层850hPa干湿区交界中的露点锋区，而高层700hPa和500hPa的水汽输送却主要是通过西北气流来实现的。  相似文献   

数值产品在2001年主汛期暴雨过程中的释用     

王海艳郝齐芬  宁德峰张时英 《河南气象》2003,(2):24-25

利用天气学暴雨天气形势概念模式，根据KCMWF数值预报产品，提前2天预报出7月22和30日的暴雨过程；日本传真图预报的降水量和物理量，也满足多年使用日本传真图总结出的强降水指标。  相似文献   

速流结构防治泥石流的理论及应用   总被引：17，自引：4，他引：17  

陈洪凯  唐红梅 《中国地质灾害与防治学报》2004,15(1):11-16

作为一种公路沿线发育的地质灾害，泥石流是路基、路面及相关建、构筑物最强烈的毁损动力。为了防治泥石流公路灾害，作者开发了速流结构。该结构由汇流槽和速流槽组成。其中汇流槽的侧墙长度、高度’、厚度等参数通过泥石流沟形态及其冲击力综合确定；而速流槽的宽度、侧墙及纵横断面则由泥石流排泄量、流速、锁固桩及流体性质综合确定。根据公路穿越速流结构的方式，将速流结构分为底越式和顶越式2种。速流结构对于解决具有大冲大淤特性的冲淤变动型沟谷泥石流灾害具有重要应用价值。据此可以确保穿越泥石流沟的公路构、建筑物的安全与稳定．确保公路交通有序进行。此外，文章对速流结构的一些子结构，如速流槽侧墙及锁固桩进行了力学分析。位于川西南西昌-木里干线公路的平川泥石流属于典型的冲淤变动型沟谷泥石流。该沟长度8．2km，沟床平均比降0．181，平均流速9．0m／s，沉积区宽度500m左右。为了确保该段公路交通的有序进行，作者干1999年实施了平川泥石流速流结构。通过2000年以来的研究及现场测试，显示了该防治结构的优越性。但是，作为一种特殊的水工结构，泥石流对速流结构的磨蚀作用是比较强烈的。因此，开展速流结构的抗冲、抗撞研究是进一步研究具有重要价值。  相似文献