大气对黑潮延伸区中尺度海洋涡旋的响应——冬季暖、冷涡个例分析     

马静  徐海明  董昌明 《大气科学》2014,38(3):438-452

采用动态合成、带通滤波等方法,通过对冬季黑潮延伸区暖、冷两个中尺度海洋涡旋的分析,研究了大气对中尺度海洋涡旋的响应特征。结果表明,海表温度（SST）与近海面风速的正相关关系在涡旋的动态合成图上清晰可见,暖（冷）涡上空对应10 m风速的极大（小）值,即海洋对大气的强迫作用在日时间尺度上表现显著;SST高低值中心基本对应10 m风无辐散区,暖（冷）涡上空为异常正（负）涡度分布;暖（冷）涡上空潜热、感热通量增大（减小）,降低（增大）大气稳定度,从而加强（减弱）边界层垂直混合作用,使得海洋大气边界层增厚（变薄）。暖（冷）涡旋上空对应摩擦速度极大（小）值,反映了湍流粘性力在高（低）海温中心增大（减小）的特征,表明动量垂直混合机制在中小尺度海气相互作用中起着主要作用。中尺度海洋涡旋能够影响大气瞬变扰动,大气瞬变扰动强度在暖（冷）涡下游上空出现极大（小）值,该影响不仅表现在海洋大气边界层,在自由大气中低层也有较为清晰的反映。此外,从能量转换的角度入手,发现斜压能量转换在中尺度海洋涡旋影响大气瞬变扰动强度中贡献明显。  相似文献   

保护地震监测环境与经济建设快速发展的思考   总被引：1，自引：0，他引：1  

王锋吉  张刚  卢仲斌  公璐 《国际地震动态》2013,(11):5-12

随着经济的发展,地震观测环境受到的干扰越来越严重。本文阐述了山东地区地震监测环境的现状,引述了山东省在经济建设中地震监测环境受到影响和破坏的实例,分析了产生的原因,结合山东省地震监测环境保护的实例探讨依法保护的意义,通过郯城地震台等监测环境保护实践活动,认识到法律、法规是地震监测环境得到保护的重要保障;阐述了依靠当地政府及其管理部门共同做好地震监测环境保护工作的必要性,并认为,应从加强县级地震机构建设及合理规划地震监测台网等方面入手,加强对地震监测环境的保护。进而提出了实现经济建设发展和保护地震监测环境矛盾统一的构想。地震台站工作人员要加强法律、法规的学习和运用,担负起地震台站监测环境保护的任务。同时,针对遇到的问题,提出了一些工作对策和建议。  相似文献   

感应式磁传感器的补偿电路     

朱旭  张世中  胡哲 《物探与化探》2012,36(6):970-974

感应式磁传感器在电磁法勘探和地震短临预测中被广泛使用.文中论述了电磁扰动观测仪中感应式磁传感器的频率补偿方法,着重介绍了感应线圈的等效电路和补偿电路,并给出了传感器的性能测试方法和主要技术指标,表明这种数字传感器适用于观测0.1～10 Hz频段内天然场源的磁场扰动.  相似文献   

Torsional Dynamic Impedance of a Tapered Pile Considering its Construction Disturbance Effect     

Wen-Bing Wu  Guo-Sheng Jiang  Shu-Hui Lü  Bang-Hua Xie 《Marine Georesources & Geotechnology》2016,34(4):321-330

The dynamic response of a tapered pile (considering its construction disturbance effect) is investigated when the tapered pile is subjected to a time-harmonic torsional loading. For most engineering conditions, the surrounding soil may be weakened or strengthened owing to the construction disturbance effect of the tapered pile, resulting in the soil becoming radially inhomogeneous. In order to consider this problem, the circumferential shear complex stiffness transfer model is proposed to simulate the radial inhomogeneity of soil. Then, the governing equations of a tapered pile-soil system subjected to torsional dynamic loading are established. By virtue of the circumferential shear complex stiffness transfer method and the impedance function transfer method, the analytical solution of torsional dynamic impedance at the head of the tapered pile is derived. Based on the presented solution, the influence of the construction disturbance effect of the surrounding soil on the torsional dynamic impedance at the pile head is investigated within the low-frequency range concerned in the design of a dynamic foundation. The results show that, even if the hardening range and softening range of the surrounding soil vary within a smaller scale, the hardening effect and softening effect also have a notable influence on the torsional dynamic impedance at the pile head.  相似文献   

Response of Sedimentary Nucleic Acids to Benthic Disturbance in the Central Indian Basin     

C. E. G. Fernandes  M. J. B. D. De Souza  Shanta Nair  P. A. Loka Bharathi 《Marine Georesources & Geotechnology》2013,31(4):289-297

Information on the response of nucleic acids (i.e., DNA and RNA) to simulated benthic disturbance was obtained from samples collected from eight sediment cores (0–10 cm) located in the Central Indian Basin (CIB). In general the total sedimentary DNA (DNA) increased with depth (from 380.09 to 408.99 μg·g^?1), while total sedimentary RNA (RNA) decreased (from 878.13 to 484.16 μg·g^?1). Following the simulated benthic disturbance brought about by the benthic hydraulic disturber, DNA decreased by 10% along the disturbed track while the RNA increased by around 75%. The RNA/DNA ratio decreased nearly 10%. However, the ratio doubled along the disturbed track suggesting that the activity was stimulated at molecular level following artif icial disturbance. The nucleic acid ratio thus shows that the CIB sediments are metabolically active, and with disturbance the activity tends to increase further.  相似文献   

Restoration of Deep-Sea Macrofauna after Simulated Benthic Disturbance in the Central Indian Basin     

B. S. Ingole  S. Pavithran  Z. A. Ansari 《Marine Georesources & Geotechnology》2013,31(4):267-288

ABSTRACT

Macrofaunal communities of the Central Indian Basin (CIB) were sampled with a spade before (June 1997), and immediately after (August 1997), and 44 months (April 2001) after a simulated benthic disturbance for polymetallic nodule mining. The average density recorded down to a sediment depth of 40 cm ranged from 89 to 799 ind·m^?2 (mean: 373 ± 221 SD; n = 12) and 178–1066 ind·m^?2 (mean: 507 ± 489 SD; n = 3) in the test and reference area, respectively. Most of the macrobenthic animals (64%) were concentrated in the upper 0 to 2 cm sediment layers, whereas, sizeable fauna (6%) inhabited the 20–40 cm sediment section and the deepest 5 cm section from 35–40 cm contributed only about 2% to the total population density. The fauna, comprised of 12 groups, were dominated by the nematodes, which constituted 54% of the total population. The macrofaunal density in the test site showed a significant increase (x:400 ind·m^?2) in the 44 months postdisturbance sampling (x:320 ind·m^?2). The population of nematodes and oligochaetes was nearly restored after 44 months, but the polychaetes and crustaceans did not reach the baseline populations measured in June 1997. The top 0–2 cm sediment layer was severely affected by the disturber, and the study suggests that physically disturbed deep-sea macrofauna may require a longer period for restoration and resettlement than normally believed.  相似文献   

Alterations in Geochemical Associations in Artificially Disturbed Deep-Sea Sediments     

B. Nagender Nath  G. Parthiban  S. Banaulikar  Subhadeep Sarkar 《Marine Georesources & Geotechnology》2013,31(4):373-400

In view of the role of Sediment geochemistry in regulating the benthic ecosystem, diagenetic remobilization of dissolved constituents, bottom water redox, and regeneration of benthic fluxes, surficial sediments in and around the track disturbed by a “benthic disturber” were studied for metal variation in three phases: (1) before the disturbance, (2) immediately after the disturbance, and (3) during monitoring of restoration after ~44 months, from the same locations. Minor variations in metal concentrations before the disturbance ere noticed indicating the homogeneity in the area or supply from similar source areas. Terrigenous fraction determined normatively from titanium contents in these sediments ranges between 40 and 47%. Most of the elements analyzed showed reduced average concentrations immediately after the disturbance suggesting physical removal and resedimentation in other areas with the migration of the plume. All the elements showed positive relation and coherence in the sediments collected after the disturbance, irrespective of their susceptibility to changes in provenance and depositional environment, whereas elemental associations during the predisturbance and monitoring periods can be explained by the known geochemical processes. The changes in Al, Ti, excess aluminium contents, their interelement relations, and factor analyses, suggest the possible transformation of clay mineral type due to the benthic disturbance that would involve changes in surface chemistry of clays. Interelement relations among redox-sensitive elements have also changed with time. This includes decoupling of Co from Mn after 44 months, probably due to the varying oxidation kinetics of two major oxides, Fe and Mn. Model calculations suggest increased diagenetic remobilization rates of Mn during the monitoring phase. Substantial increase in redox-sensitive elements, especially Fe and Mn indicate oxygenation of bottom water due either to reduced activity of benthic burrowing organisms or to renewal of oxygen-rich Antarctic Bottom water (AABW). Increase in these elements is consistent with the results of the HEBBLE experiment, where the burrows seem to protect these elements from strong bottom currents. Restoration of predisturbance values in the terrigenous component is attributed to the influence of shifts in the direction of bottom flow and suggests that bottom currents would play a major role in restoring the lithogenic component by transporting it from other locations within the Basin during commercial mining operations.  相似文献   

Response of Meiofauna to Immediate Benthic Disturbance in the Central Indian Ocean Basin     

B. S. Ingole  Z. A. Ansari  V. Rathod  N. Rodrigues 《Marine Georesources & Geotechnology》2013,31(3):263-272

Abstract

Twenty-four stations (12 each, during pre- and postdisturbance studies) 5300 to 5330 m deep between 10°01' and 10°03'S latitude and between 75°59' and 76°02'E longitude were sampled to study the effect of benthic disturbance on the distribution of meiofauna in the Central Indian Ocean. Bottom-sampling was conducted with a box corer. Total meiofauna density ranged from 35 to 45 organisms per 10 cm² of bottom area during the predisturbance period and 21 to 32 organisms per 10 cm² during the postdisturbance period in the test and reference sites. Differences between pre- and postdisturbance study results were statistically significant (P < 0.05). Nematoda was the most abundant meta-zoan group, on an average representing >55% of the meiofaunal population. The abundance of nematodes and harpacticoid copepods as well as total meiofauna showed marked decreases during postdisturbance sampling. Vertical distribution of meiofauna in the sediment cores revealed that 75% to 90% of the metazoan population was confined to the top 2-cm layer of the sediment. Recolonization experiments suggest that harpacticoid copepods may take more time for recolonization than the nematodes and are more sensitive to the physical disturbance. These findings suggest that nematodes and harpacticoid copepods can be used as indicator organisms in recolonization experiments.  相似文献   

Self-expanded piles: A new approach to unconventional piles development     

Ebrahim Shojaei  Navid Ganjian 《Marine Georesources & Geotechnology》2021,39(1):115-128

Abstract

In onshore and offshore fields of ocean engineering, piles are used as foundation systems for various structures. Piles are classified into different types depending on their materials, geometries, and particularly, installation methods, which have advantages or limitations. Companies and engineers have developed a new group of piles, because of necessity to improve their performance in terms of increasing the bearing capacity, reducing impacts of traditional installation procedures, implementing by low- torque power equipment, and utilizing them in widely different ground conditions, including in a marine environment. In the present study, three different models of a new pile with an expander body are introduced to increase the shaft and pile-toe diameters and its self-expansion in the embedment depth under the titles of the Bubble pile (BP), Self-Expanded pile (SEP) and Wing pile (WP). The main subject of this research is to achieve increased bearing capacity, reduced installation effects, and decreased required installation torque. The frustum-confining vessel of Amirkabir University of Technology (FCV-AUT) was employed for this purpose. Up to 14 axial compressive and tensile load tests were carried out on different model piles on sand collected from Anzali shore located on the northern coast of Caspian Sea in Iran, with relative densities of 45% to 50% within FCV-AUT. Comparing the performance of introduced pile with traditional pile corresponding to the same characteristics, the results indicated a significant increase in the axial bearing capacity and reduced disturbance effect of the pile. Also, a lower installation torque of the SE pile was required compared to the helical pile. The test results also demonstrated that the new pile could resist considerable compressive and uplift loads, and could be a possible alternative to traditional piles in the onshore sector.  相似文献   

Effects of mechanical macrophyte control on suspended sediment concentrations in streams     

MJC Greer  AS Hicks  SK Crow  GP Closs 《新西兰海洋与淡水研究杂志》2013,47(2):254-278

Suspended sediment (SS) is an important pollutant in freshwater ecosystems and can be detrimental to fish communities. Although macrophytes mediate sediment deposition, little effort has been put into determining how their removal affects sediment resuspension. The present study examined the immediate and long-term impacts of mechanical macrophyte removal on SS concentrations in streams. The results of this study suggest that bed disturbance during mechanical excavation of macrophytes significantly increases SS in the short term, and concentrations were found to increase by as much as 15,687 mg L^–1 immediately after macrophyte removal. Significant long-term (77 day) increases in SS were also observed, indicating that without macrophytes, disturbed material is continually resuspended after excavation by fluvial processes. These results demonstrate that macrophyte removal can result in SS levels that have previously been shown to harm fish, and indicate that this activity may be more detrimental to fish than previously thought.  相似文献