Tidal effects on estuarine circulation and outflow plume in the Chesapeake Bay     

Xinyu Guo  Arnoldo Valle-Levinson 《Continental Shelf Research》2007

The response of the Chesapeake Bay to river discharge under the influence and absence of tide is simulated with a numerical model. Four numerical experiments are examined: (1) response to river discharge only; (2) response to river discharge plus an ambient coastal current along the shelf outside the bay; (3) response to river discharge and tidal forcing; and (4) response to river discharge, tidal forcing, and ambient coastal current. The general salinity distribution in the four cases is similar to observations inside the bay. Observed features, such as low salinity in the western side of the bay, are consistent in model results. Also, a typical estuarine circulation with seaward current in the upper layer and landward current in the lower layer is obtained in the four cases. The two cases without tide produce stronger subtidal currents than the cases with tide owing to greater frictional effects in the cases with tide. Differences in salinity distributions among the four cases appear mostly outside the bay in terms of the outflow plume structure. The two cases without tide produce an upstream (as in a Kelvin wave sense) or northward branch of the outflow plume, while the cases with tide produce an expected downstream or southward plume. Increased friction in the cases with tide changes the vertical structure of outflow at the entrance to the bay and induces large horizontal variations in the exchange flow. Consequently, the outflow from the bay is more influenced by the bottom than in the cases without tide. Therefore, a tendency for a bottom-advected plume appears in the cases with tide, rather than a surface-advected plume, which develops in the cases without tide. Further analysis shows that the tidal current favors a salt balance between the horizontal and vertical advection of salinity around the plume and hinders the upstream expansion of the plume outside the bay.  相似文献   

河套地区4~5月雨量变化周期特征及其趋势预测   总被引：1，自引：0，他引：1  

郭新宇  蒋全荣 《南京气象学院学报》2001,24(4):576-580

Morlet子波分析表明，河套地区4－5月雨量明显存在7a,24a和3a周期，其中以7a周期为最强。用子波分析和周期图方法预测该地区4－5月在2000－2003年雨量将持续偏少，2004或2005年雨量可能会明显偏多。  相似文献   

拉张状态下方解石组构的递进变形规律     

宋传中  钱德玲 《西北地质科学》1995,16(2):23-28

拉张状态下方解石组构多星环带到，递进变形状态下才可能出现点极密．因为当分解剪应力达最大值时，含有众多方解石颗粒的岩石中，形成ｅ双晶滑动最有利的方位不可能是唯一的，而是不同方位的滑动系在三维空间中的组合，并且ｅ双晶极点和光轴各自构成古钟型。由于系同一应力作用下的产物，二钟型体的顶角大小不同，但彼此共轴，均平行主任应力方向，属共轴叠钟体。该叠钟体记录了岩石变形时的应力状态，未再变形之前，该组构为初始组构。岩石的递进变形过程，实际是初始组构的递进变形过程，最后形成定型组构．岩石递进变形的全过程，就是初始组构到定型组构的全过程．  相似文献   

首届全国地震工作好新闻评选活动概况     

柴保平  王伟 《国际地震动态》1993,(6):17-19

  相似文献   

长庆气田奥陶系风化壳气藏、气源研究   总被引：22，自引：4，他引：18  

戴金星  夏新宇 《地学前缘》1999,6(Z1):195-203

对10年来长庆气田奥陶系风化充气藏气源问题存在的不同观点（上古生界煤成气和奥陶系海相碳酸盐岩气何者为主）及相应的证据进行了总结和讨论,认为“奥陶系自生自储为主”的观点对地质和地球化学现象的解释存在疑问,包括用次要组分来判别混源天然气的主要来源,用不确切的端员气地球化学特征来计算混源比,对本溪组底部岩石的封盖性和下奥陶统碳酸盐岩的原始生烃潜力评价偏高,忽略了石炭系存在能够生成油型气的海相源岩。因此,长庆气田不能作为海相贫有机质的碳酸盐岩生成的大、中型油气田的实例。根据天然气及气源岩的地球化学特征,提出长庆气田奥陶系风化壳气藏气是以上古生界煤成气为主、石炭系海相源岩生成的油型气为辅的混合气。  相似文献   

Effect of near-fault earthquake on bridges: lessons learned from Chi-Chi earthquake   总被引：4，自引：1，他引：3  

Chin-Hsiung?LohEmail author  Wen-I?Liao  Juin-Fu?Chai 《地震工程与工程振动(英文版)》2002,1(1):86-93

The objective of this paper is to describe the lessons learned and actions that have been taken related to the seismic design of bridge structures after the Chi-Chi, Taiwan earthquake. Much variable near-fault ground motion data was collected from the rupture of Chelungpu fault during the Chi-Chi earthquake, allowing the seismic response of bridge structures subjected to these near-fault ground motions to be carefully examined. To study the near-fault ground motion effect on bridge seismic design codes, a two-level seismic design of bridge structures was developed and implemented. This design code reflects the near-fault factors in the seismic design forces. Finally, a risk assessment methodology, based on bridge vulnerability, is also developed to assist in decisions for reducing seismic risk due to failure of bridges. Director of Center for Research on Earthquake Engineering. Supported by: the Science Council, Chinese Taipei, under grant no. SC 90-2211-E-002-028.  相似文献   

相似变换在大比例尺地形图的投影换带中的应用     

房新玉  闻道秋  张秀梅  李娜 《现代测绘》2006,29(6):36-38,48

在大比例尺地形图的使用过程中，会遇地形图的坐标系变换，需要把中央子午线为L1的坐标系的地形图转换成中央子午线为L2的坐标系的地形图，称之为地形图投影变换。目前许多地形图是以电子地图形式存在的，是通过AUTOCAD软件形成的。基于此，本文提出了适用于AutoCAD中地形图投影换带的方法：相似变换法。即在满足精度要求的情况下，利用相似变换原理，对AutoCAD中的地形图进行平移，旋转，缩放变换，最终将其变换到需要的坐标系内。  相似文献   

LA-ICPMS U-Pb Ages of Zircon from Metaleucosomes, Olongbuluke Microcontinent, North Qaidam, and Implications on the Response to the Global Rodinia Supercontinent Assembly Event in NW China   总被引：1，自引：0，他引：1  

王树庆李晓彦陈能松王新宇  王勤燕柳小明 《中国地质大学学报(英文版)》2006,17(3):238-245

INTRODUCTION The Olongbuluke microcontinent , which wasdisintegratedfromthe northern margin of the Qaidamblock (Lu,2002) ,is composed of a two-fold base-ment with cover strata . The lower basement is themedium- to high-grade Delingha complex and theDakendaban Group, and the upper is the low-gradeWandonggou Group. The Wandonggou Group of theupper basement experienced a Late Mesoproterozoicmetamorphic event (see Yu et al .,1994) ,consistentwith the early isotopic geochronological respo…  相似文献   

Determination of Bromine and Iodine in Twenty-three Geochemical Reference Materials by ICP-MS   总被引：1，自引：0，他引：1  

Jian Y. Chai  Yasuyuki Muramatsu 《Geostandards and Geoanalytical Research》2007,31(2):143-150

Trace amounts (from nanogram to microgram levels) of bromine and iodine were determined by inductively coupled plasma-mass spectrometry (ICP-MS) in twenty-three geochemical reference materials issued by the GSJ, USGS, IAEA etc. The pyrohydrolysis technique was used to separate bromine and iodine from samples analysed in the form of powder. The accuracy and precision of the experimental values were assessed by the comparative analysis of well established reference materials such as USGS AGV-1, BCR-1 and IGGE GBW07312. The measured values agreed well with reported values within a 10% error range. We also report reliable new data for these elements in these geochemical reference materials.  相似文献   

星载加速度计的动力法校准   总被引：1，自引：0，他引：1  

邹贤才  李建成  罗佳  徐新禹 《武汉大学学报(信息科学版)》2007,32(12):1152-1155

通过模拟轨道，利用动力法对星载加速度计校准进行了研究。用不同参考重力场模型获得的校准参数分别重新积分卫星轨道，与模拟轨道的差异最大可达m级。结果表明，参考重力场模型误差对加速度计校准的影响不可忽略，在校准加速度计的同时应解算重力场模型，以削弱模型误差的影响。  相似文献