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从描述f平面上的正压地形拦截波的非线性动力方程出发,利用常微分方程定性理论研究了海底地形坡度和海底摩擦对线性和非线性地形拦截波的动力不稳定性的影响,分析了不稳定的性质,找出了不稳定的判据。还在特定的海底地形坡度和海底摩擦条件下,建立了线性和非线性波的频散关系,并比较了两者的差别。 相似文献
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地形斜坡对东海黑潮陆架坡折锋稳定性影响研究 总被引：1，自引：1，他引：0
为了研究地形斜坡对东海黑潮陆架坡折锋稳定性的影响,利用简化的线性原始方程,在一定背景流的情况下,主要从增长率、相速度、空间结构和能量方面分析海底地形斜坡变化对坡折锋稳定性的影响。模式结果表明,平底地形时,扰动的强度大且扰动区域广,但有地形斜坡时,扰动区域变窄,强度变弱,地形对坡折锋起稳定性作用。通过能量分析得出东海黑潮陆架坡折锋是正压和斜压的混合不稳定,其中斜压不稳定占主导地位。实验分析得出,地形对东海黑潮陆架坡折锋起稳定作用,斜坡增大,斜压不稳定和正压不稳定均减弱,斜压不稳定减弱更明显。 相似文献
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采用不同年代的水深图和物质来源测量资料,研究了青岛港外航道开挖区的海床演变情况。分别利用等深线、区域地形及海底地形剖面来对比水深地形变化,研究开挖区的地形冲淤变化,结果表明拟开挖航道区近70 a来,其海床演变主趋势为轻微侵蚀,而其南北两侧的邻近海域海底地形变化则既有局部侵蚀又有局部淤积;通过外航道开挖区域11个观测点测量的有关水流、底沙粒径等数据计算分析,得到其开挖后淤积厚度在0.453~4.149 cm/a之间。青岛港外航道开挖区年平均回淤速率不大,适合扩建。 相似文献
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以南黄海江苏岸外辐射沙脊群为对象,基于已验证的该区域沉积动力学数值模型模拟近30 a(1979~2011年)的水下地形演化,计算辐射沙脊区域海底地形年际变化标准偏差,对沙脊和水道的地貌稳定性进行定量评估。研究发现,地形变化标准偏差愈小,地貌愈稳定;标准偏差愈高,地貌愈不稳定。定量地确定了南黄海辐射沙脊区域内沙脊与水道稳定性系数的时空分布,发现主要淤积区域位于沙脊周围,近岸沙洲有淤高的趋势;主要侵蚀区位于水道,沙脊间水道逐渐冲刷加深,如西洋水道和黄沙洋水道。本研究提出的基于海底地形年际变化标准偏差确定地貌稳定性评估方法,可为海岸陆架地貌稳定性研究、区域资源开发和环境保护等提供参考。 相似文献
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利用卫星合成孔径雷达(SAR)图像信息探测海底地形是海洋遥感物理学和海洋动力学研究具有挑战性的问题,这是因为根据电磁波传播原理,雷达脉冲没有能力穿透海水,因而不可能直接探测到海底地形特征,可是,许多卫星SAR图像上确实显示出海底地形特征。这些海底地形不仅分布在水深小于100m的浅海,而且在600~800m甚至2 000~3 000m的深海区也有发现。本文概略介绍该领域的发展前沿和研究进展,主要内容包括海面过程雷达成像基本理论,我国辽东浅滩、台湾滩以及美国东部湾流海域等3个海区海底地形特征SAR成像理论:分别为速度切变流纵向流经平行海底地形、层化流体横向流流经平行(周期性)海底地形和强海流流经孤立海底地形。据此建立的理论和分析方法可做为研究更复杂情况和探索新应用领域的基础和出发点。 相似文献
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南海海底地形以复杂著称,适合布放沉底自容式观测仪器的海区不多。通过对南海海底地形、水深、通航条件及作业时间的科学合理分析,为南海海域海底日变站布防选址提供了有效方法并取得良好的实际效果,确保了南海水下地磁日变观测的安全性。 相似文献
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福建海坛海峡峡道动力地貌研究 总被引：2，自引：0，他引：2
从海坛海峡的形成演变规律、水动力条件、海底地形地貌及沉积特征等方面分析了海坛海峡的动力地貌特征．研究结果表明，海坛海峡峡道效应明显，因受海峡周边地形影响，区域内水动力环境及地形地貌变化复杂，分别在海峡两侧不同区域发育着岩滩、沙滩和泥滩3种地貌，在海底中发育着水下浅滩、潮流脊系和潮流三角洲3种地貌．海峡南北出口位置及海峡海底深槽海域水动力强，两侧岸滩、海滩发育，水下冲刷槽发育明显，处于弱冲刷状态，海底分布粗粒沉积物．海峡港湾内水动力弱，潮滩较发育，处于稳定至弱淤积状态，海底分布细粒沉积物． 相似文献
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Using a two-dimensional semi-geostrophic model. the stability of fronts near shelf break (shelfbreak font, western boundary current front) and its mechanism are studied. We find that the stability of the front is related to the frontal structure. In general, the increase of the lower layer depth lowers the unstable growth rate (a1). (1) The shelfbreak front is baroclinically unstable and ai increases with the increase of the bottom slope, different from the conclusion of Flagg and Beardsley (1978). (2) A western boundary current front with uniform vorticity in the upper layer is barotropically unstable, due to the strong horizontal shear of the mean current. The unstable growth rate of this front for a realistic topography is only one seventh of that of the flat bottom case. (3) For a western boundary current front with hyperbolic tangent structure, we find its wave propagation speed to be about 0. 5 m/s, in agreement with the observed values. The front is baroclinically unstable. (4)The unstable growth 相似文献
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On the basis of the data array of detailed echosounding surveys carried out from the research vessels of the Marine Hydrophysical
Institute of the Ukrainian National Academy of Sciences and other institutions and the corresponding cartographic materials,
we perform the numerical analyses of the morphometric characteristics of the bottom topography of the northwest shelf of the
Black Sea and the underwater margin of the Crimea. We reveal the specific features of the main types of morphological structures
and analyze the values of the bottom slopes and the vertical and horizontal ruggednesses of the bottom. The ruggedness of
the bottom has a low-frequency character reflecting a noticeable smoothness of the topography. The large regional structures
of the surrounding land represented by the East-European platform and the Crimean-Caucasian orogen directly affect the formation
of topography in the analyzed region. The agreement between the contemporary digital data arrays on the bottom topography
and the data of echosounding surveys in the Black Sea is estimated. 相似文献
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海滩是砂质海岸重要的沉积地貌单元,其沉积特征和稳定性对于海滩的开发利用与保护具有重要意义。本文根据海口湾西海岸海滩表层沉积物粒度数据,阐述了该区域海滩沉积物的时空分布规律,并通过对比滩面高程数据和水下地形数据分析了该区域的岸滩稳定性。结果表明：海口湾西海岸海滩处于滩面微蚀的轻度不稳定态,其岸外浅滩处于边坡侵蚀的轻度不稳定态。另外,根据波浪作用和泥沙来源进一步探讨了海口湾西海岸海滩沉积物动力机制及其海滩侵蚀的原因。 相似文献
14.
A. N. Romanov A. O. Kovrigin A. F. Lazarev V. A. Lubennikov 《Izvestiya Atmospheric and Oceanic Physics》2016,52(8):869-875
Air pollution by industry and motor vehicles, the use of coal ash for the construction of residential and nonresidential buildings, and the presence of dead zones in the residential sector are the main factors of carcinogenic risk to human health. Natural factors (such as topography and prevailing wind directions) can weaken or strengthen technogenic factors. Based on the estimate of pollutant concentrations in the snow cover of Barnaul, we reveal residential areas that are located at the crossroads of atmospheric transport of carcinogenic substances and characterized by concentrations considerably exceeding the maximum allowable concentration. These areas are characterized by the integral accumulation of carcinogenic substances concurrently from multiple sources; for almost any wind rose, the impact of one of the pollution sources is observed throughout the year. The assessment of the carcinogenic risk for a territory depends much on the correlation between local topography and the height of apartments above ground level. Using cancer register data for Barnaul, we reveal an increased level of the incidence of malignant neoplasms in people living in high-rise buildings located in areas with a sharp change in topography (such as ledges, hills, and lowlands). This may occur due to stagnant zones and wind shadows; under certain correlation between topography and the height and shape of buildings, carcinogenic substances accumulate maximally. 相似文献
15.
珊瑚礁地质稳定性研究现状 总被引：1，自引：1，他引：0
为探究珊瑚礁稳定性的研究现状,对影响礁体稳定性的诸多因素如礁体结构、地形地貌、波浪、潮汐、潮流、风诸如热带气旋和风暴、海流等进行总结,结果表明以上诸多因素可在不同程度上决定或影响礁体稳定性。同时指出现阶段礁体稳定性研究所需注意的问题,其一是涉及珊瑚礁地质稳定性的礁体结构、地貌形态的研究尚少,需合理利用多波束测深仪、高分辨率多道地震探测系统、钻探及AUV、三维实时声学成像声呐技术获取礁体地形、地层及剖面形态,并借助GIS技术对滑坡等失稳地带进行圈定,其二是潟湖区、礁体边坡等区域的稳定性研究缺乏,需引入极限平衡法评估礁体边坡、泻湖等区域的稳定性,且需考虑波浪、潮汐引入的孔隙水压力、渗流力的影响。通过综述礁体稳定性研究现状及未来礁体稳定性研究的方向的展望,以期为珊瑚礁体上的工程建设及未来的珊瑚礁地质稳定性研究提供些许启示。 相似文献
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东海西部海域工程地质条件评价 总被引：1，自引：0，他引：1
黄慧珍 《海洋地质与第四纪地质》1993,13(1):47-64
根据东海西部海域浅部地层的成因、地质年代及沉积层序,将晚更新世末以来的地层自上而下划分为Ⅰ、Ⅱ、Ⅲ、Ⅵ工程地质层。又根据所遇地层的岩性、厚度,埋藏条件及物理——力学性质的不同分若干亚层。东海西部海底不稳定因素有:地震、浅层气、滑坡、崩塌、侵蚀与沉积作用、海底地貌形态。综上因素将东海西部海域划分为:长江水下三角洲工程地质区、浙东海域工程地质区和陆架平原工程地质区。 相似文献
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强潮河口盐水入侵对饮用水源地危害极大。基于平面二维水动力盐度模型, 对典型强潮河口—钱塘江的水动力及盐水入侵过程进行了数值模拟研究。结果表明枯水径流时盐度变化与潮位过程曲线类似, 潮差对盐度大小影响显著, 径流量的增加将逐渐减小其相似程度。当流量增加到一定程度后, 继续增加的一定径流量所产生的抑咸效果减弱, 水资源有效利用率降低, 此时允许水源地盐度超标并改从蓄淡避咸水库取水可有效节约水资源。盐度平面分布显示, 盐水入侵在强潮河口弯道处受涨潮流主流线影响明显, 靠近主流线一岸的盐度大于对岸, 单从盐水入侵角度考虑, 强潮河口弯道段的取水口应设置在远离涨潮流主流线一岸。钱塘江河口盐度数值模拟对于研究减轻盐水入侵对水源地危害的措施具有指导意义。 相似文献
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The spectral analyses of moored current velocities in the central Luzon Strait reveal northward (i.e., downstream of the Kuroshio)
propagation of a frontal wave with a five-day period, with wave amplitude increasing northward. Estimated from both curve
fitting and frequency domain Empirical Orthogonal Function methods, the characteristics of five-day variations have wave speeds
ranging from 32 to 40 cm s−1, wavelengths ranging from 130 to 150 km, and e-folding time scales for growth ranging from 0.8 to 3 days. An analytical two-layer model used to explore linear stability
characteristics indicates that bottom topography (two meridional ridges) is important for the Kuroshio stability characteristics
in the Luzon Strait. In the two-layer model with the two ridges, the flow is stabilized for the long-wave mode but destabilized
for the short-wave mode (due to increasing vertical shear in the horizontal velocity). The analytical model produces wavelengths
and phase speeds for the most unstable mode which is similar to the observation, but the growth rate is underestimated. However,
a spectral numerical model applied with a more realistic stratification and velocity structure does obtain faster growth rates
comparable to the observations. Parameter sensitivity tests were conducted using the analytical model. The characteristics
of the most unstable mode are most sensitive to the surface front location relative to the bottom topography but not sensitive
to varying the density difference and thickness of the upper layer. 相似文献
19.
基于海洋灾害地质评价基础上的我国近海海底稳定性区划 总被引：3，自引：2，他引：1
通过对我国近海灾害地质类型的分析、评价进而进行海底稳定性区划研究,旨在反映近海地质环境对人类工程活动的适宜程度。文中提出了海底稳定性评价的概念,构建了以地震动、工程地质、地貌、直接型灾害地质类型和限制型灾害地质类型为主要评价指标的海底稳定性评价指标体系,并利用层次分析法确定了各评价指标权重值;将我国近海海底划分为6′×6′的网格单元,并以近海海底灾害地质图、地震动峰值加速度区划图和地貌图等矢量化图层为数据源,建立了模糊评价模型并对近海海底稳定性进行了定量评价。在此基础上将我国近海海底区域稳定性从稳定到不稳定划分为五级。 相似文献
20.
The shelfbreak wintertime thermal front in the Northeastern Gulf of Mexico often exhibits meandering, eddy formation and warm-water
intrusion. A high level of frontal variability plays an essential role in exchange processes across the shelf. This study
examines the impacts of local frontal instability and bottom topography on turbulent heat exchange across the front using
the results of two numerical models. Analysis of a series of numerical experiments reveals that the flow is baroclinically
unstable. Predicted frontal instability contributes significantly to cross-frontal exchange and accounts for about 35% of
the total eddy heat flux. Onshore eddy heat flux has the highest intensity at the frontal position. In addition, eddy activity
and heat flux are sensitive to variation of bottom topography. For topographic features and frontal characteristics that are
typical of the area, bottom steepness enhances the flux and is nearly proportional to the cross-frontal heat exchange. The
study attempts to explain physical mechanisms that drive frontal circulation in the area and to quantify heat transport across
the shelf. Estimated heat fluxes can provide important information for climate and ecosystem modeling of the Mississippi Bight. 相似文献