共查询到20条相似文献，搜索用时 31 毫秒
1.
In this paper we develop further the satellite radiothermovision methods for analyzing the evolution of tropical cyclones. The complicated case of Goni and Atsani interacting typhoons is considered. It has been shown that, although their interaction does not explicitly influence the features of the typhoon trajectories, indications of the formation of complex advective fluxes in the lower troposphere can be revealed from both a qualitative analysis of miscellaneous satellite data and a quantitative estimation of latent heat advection. At the same time, in contrast to the previous works, we had to introduce the integration contours of a complex form (differing from a circular one) into the analysis, so that the energy balance of the typhoon system is correctly described. In a general way, defining such contours is a separate problem whose solution is probably related to the invocation of a large volume of additional satellite information. Due to the peculiarity of the considered case of Goni and Atsani twin typhoons, we demonstrated the effectiveness of a simplified approach that uses a composite contour formed by overlapping two circular ones. Generally, as in the cases previously considered, we found the interrelation between the intensification and dissipation of typhoons (tropical cyclones) and the modes of convergent and divergent advection of latent heat with amplitudes sufficient to support the total power of the system. 相似文献
2.
《Applied Ocean Research》2004,26(3-4):137-146
A theoretical approach is applied to predict the propagation and transformation of nonlinear water waves. A semi-analytical solution was derived by applying an eigenfunction expansion method. The solution is applied to analyze the effect of wave frequencies and wave steepness on the propagation of nonlinear waves. The main attention is paid to the wave profile, the wave energy spectrum, and the changes of wave profile and energy spectrum due to the interaction of wave components in a wave train. The results show that for waves of low steepness the nonlinear wave effects and effects associated with the interaction of water waves in a wave train are of secondary importance. For waves of moderate steepness and steep waves the effects associated with the interactions between waves in a wave train are becoming significant and a train of initially sinusoidal waves may drastically change its form within a short distance from its original position. The evolution of wave components has substantial effects on the wave spectrum. A train of initially very narrow-banded waves changes its one-peak spectrum to a multi-peak one in a fairly short period of time. Laboratory experiments were conducted in a wave flume to verify theoretical approaches. The free-surface elevation recorded by a system of wave gauges was compared with the results provided by the semi-analytical solution. Theoretical results are in a fairly good agreement with experimental data. A reasonable agreement between theoretical results and experimental data is observed often even for relatively steep waves. 相似文献
3.
用直接法分析超大型浮体的水弹性响应 总被引：4，自引：2，他引：2
探讨了浮舟桥型超大型浮体结构的水弹性响应分析问题。将超大型浮体结构简化成弹性平板模型,用压力分布法计算流体压力,用直接法计算流体-结构系统,给出了它们的数学计算模型。计算表明本计算方法和程序是正确的,并能保证充分的精度,进而计算了更大尺度的超大型浮体,分析了波长、波向等对响应振幅的影响。 相似文献
4.
S. A. Ermakov I. A. Kapustin O. V. Shomina 《Izvestiya Atmospheric and Oceanic Physics》2014,50(2):204-212
Investigation of damping of gravity-capillary waves (GCWs) in the presence of turbulence is a classical hydrodynamic problem which has important geophysical applications, one of which is related with the problem of forming a radar and optical image of a ship wake on wavy water surface. In this work a new method for the laboratory study of surface wave damping in turbulized liquid is described and the results are presented. The damping of standing GCWs by turbulence on the water surface in a tank mounted on a vibration table is studied. GCWs and turbulence are excited using a two-frequency mode of vibration table oscillations. A high-frequency small amplitude signal is used for parametric GCW excitation; a low-frequency large amplitude signal is used for generating turbulence due to water flowing through a fixed perforated grid submerged into the tank. The coefficient of GCW damping is determined by measured threshold of parametric excitation of the waves; turbulence characteristics are determined by the PIV and PTV techniques. Dependences of GCW damping coefficients on their frequency at different turbulence intensities are obtained, estimates for turbulent viscosity are presented, and a comparison with empirical models proposed earlier is performed. 相似文献
5.
M. I. Fortus 《Izvestiya Atmospheric and Oceanic Physics》2006,42(1):124-126
We analyze series of tree-ring indices to understand whether they can be indicators of long-term climate changes. We calculated the synchronous cross-correlation coefficients (CCs) for all possible pairs composed of nine series, of which only one CC (for a pair of the longest series) proved to be sufficiently high (0.72). We revealed a time interval for which this CC is equal to 0.88. We failed to locate sufficiently larger time intervals with a higher CC for other pairs of series. Similar calculations for a series using a low-frequency filter (with allowance for periods of 100 or more years) led to a noticeable decrease in almost all CCs. This confirms the statements circulating in the literature that tree-ring chronologies include climate signals with characteristic times of several decades and that the secular and supersecular oscillations are significantly distorted as a result of standardization and cross-linking. The results presented in this paper show that the complex of series being considered cannot be used as a climate-change indicator without an additional analysis. Here, we describe a possible procedure for such analysis. As a result, we found that only two time series at some time subinterval can provide useful information about climate changes. 相似文献
6.
Hideo Kawai 《Journal of Oceanography》1986,42(1):22-29
Avoiding the subject for fish accumulation, the traditional view in fish population dynamics has ascribed immigration and emigration of fish to dispersal of fish. The main purpose of this paper is to find a quantity that represents the time rate of accumulation-dispersal of marine organisms, and also has some relation to the horizontal convergence of current velocity of the surrounding water. For this, the accumulation-dispersal coefficient is introduced not in the form of diffusion, but in the same form as the convergence. Since the accumulation-dispersal of organisms is a factor that changes its distribution density, all factors causing the change are first classified to locate the position occupied by the accumulation dispersal. Each factor corresponds to each coefficient appearing in a linearized equation describing the rate of change in the density, averaged over a region or a group. The immigration-emigration coefficient is divided into three coefficients of passage, accumulation dispersal and diffusion velocity. For the organisms ranging in a nearly horizontal layer, the accumulation-dispersal coefficient is shown to equal the area-averaged horizontal convergence of organismal velocity relative to land, which is the sum of the area-averaged horizontal convergences of swimming velocity relative to water and of current velocity. However, the area-averaged convergence of current velocity associated with the accumulation-dispersal coefficient for a region is shown to be somewhat different from the usual one. 相似文献
7.
8.
利用透射电镜观察大竹蛏(Solen grandis Dunker)精子发生和精子的超微结构,描述了从精原细胞发育到成熟精子过程中超微结构的变化。大竹蛏精子发生历经精原细胞、初级精母细胞、次级精母细胞、精细胞和成熟精子5个阶段。成熟精子属典型的原生型,全长52—57 μm,由头部、中段和尾部三部分组成。头部由顶体和细胞核组成;中段由4—5个椭圆形线粒体和2个相互垂直的中心粒组成;尾部细长,为典型的“9+2”型结构。大竹蛏与同属的长竹蛏精子发生和精子超微结构存在差异。大竹蛏精细胞前顶体囊的高电子密度物质分布在周缘呈一个带缺口的弧形而不是圆形,而长竹蛏前顶体囊周缘的高电子密度物质呈一圆形分布;大竹蛏的前顶体囊是先内凹变形,然后一边变形一边移动,而长竹蛏的前顶体囊是在到达核前端后才开始变形。大竹蛏的顶体比长竹蛏的稍长;大竹蛏精子核形似子弹头而长竹蛏精子核形为圆球状;大竹蛏有卫星体结构而长竹蛏无卫星体结构;大竹蛏精子尾部鞭毛比长竹蛏的长。结果可以为竹蛏科相似种类的鉴定及亲缘关系的探讨提供参考依据。 相似文献
9.
Norihisa Usui Hiroyuki Tsujino Hideyuki Nakano Satoshi Matsumoto 《Journal of Oceanography》2013,69(6):647-670
This study investigates the long-term variability of the Kuroshio path south of Japan. Sensitivity experiments using a data-assimilative model suggest that the duration of the large meander (LM) strongly depends on the Kuroshio transport; specifically, low transport leads to a long duration of the LM. Actually, we find a good correlation between the duration of the past LMs and the Sverdrup transport estimated by a wind-driven linear baroclinic vorticity model. Then we explore favorable conditions for the LM and find a close relationship between the Kuroshio Extension (KE) state and the LM. That is, a precondition for the LM that the Kuroshio path on the Izu Ridge is fixed at a deep channel located around 34°N is achieved during a stable KE state. In addition, westward propagating signals with negative anomalies in the Kuroshio region and high sea-surface height (SSH) state east of Taiwan are key for generation of a small meander southeast of Kyushu that triggers a subsequent LM. The signals related to the above conditions change the upstream Kuroshio transport and velocity, which are consistent with features indicated by the former observational studies. Using reanalysis data, we construct long-time series of indices for the three conditions, which explain well the past LMs. The indices suggest that long-term non-LM states around 1970 and in the 1990s were attributed to a low-SSH state east of Taiwan and an unstable KE state, respectively. 相似文献
10.
In many engineering problems one deals with quantities that must be considered to be of a stochastic or random nature. This is true for the natural environment such as wind, waves, and earthquakes, which are the driving mechanism behind the loadings on a wide variety of land-based and offshore structures. From a design perspective it is important to determine the expected highest value of a stochastic process, and structural fatigue life. The relevant procedures are reasonably well established for processes that have narrow band spectra, but it is much less clear how to deal with non-narrow band cases. In this paper it is shown that the extremes of a Gaussian, non-narrow band process are asymptotically equal to the extremes calculated according to the narrow band formula. Also demonstrated is that fatigue estimates may, with good accuracy, be based on the narrow band formula unless the bandwidth becomes extremely large. These statements are illustrated by examples of a process with (1) a low pass box spectrum, and (2) a Pierson–Moskowitz wave amplitude spectrum. It is also shown that the bandwidth parameter may in some cases be counter-intuitive, as the Pierson–Moskowitz spectrum has a larger bandwidth parameter than the box spectrum, even when both cover the same frequency range. 相似文献
11.
1984～2012年海州湾海岸线时空演变研究 总被引：4，自引：2，他引：2
以Landsat影像为数据源, 通过改进归一化水体指数、二值化、潮位校正模型提取海岸线, 使用数字海岸线分析系统(Digital Shoreline Analysis System, DSAS), 对1984～2012年海州湾海岸线的时空演变进行了研究。结果表明, 1984～2012年间海州湾海岸线整体以4.29 m/a向海洋推进, 其中, 48%的海岸出现侵蚀, 侵蚀速率为22.83 m/a, 侵蚀现象主要出现在大堤修建前的部分粉砂淤泥质海岸。52%的海岸出现淤积, 淤积速率为25.90 m/a, 淤积现象主要出现在人工海岸、河口海岸和受大堤影响的粉砂淤泥质海岸。海岸线时空演变研究有利于科学地规划、开发和管理海洋及其沿岸空间资源, 并保证其环境及经济的可持续发展。 相似文献
12.
Matao Takagi 《Ocean Engineering》1981,8(6):623-644
A method of simulation calculation for a mooring system of vessels inside a breakwater is illustrated. Using a simulation program based on the above method, a test design for a mooring system for oil-storage vessels of total 5.6 million kiloliters was conducted.In order to obtain data for the simulation program, various experiments, such as wind tunnel tests to test wind resistance, and wave tank tests to test the waves transmitted through or over the breakwater, and the motions of vessels inside the breakwater due to waves, were conducted.Some proposals concerning design criteria and safety factors are presented.Finally, the results of the test design under estimated sea and weather conditions are shown, and the design is concluded to be both technically and economically feasible. 相似文献
13.
采用扫描和透射电镜技术, 观察刺巨藤壶(Megabalanus volcano)精子发生和精子的超微结构特征。结果显示, 刺巨藤壶精子发生经历精原细胞、初级精母细胞、次级精母细胞、精细胞和精子等5个阶段。在精子形成期间, 圆形或椭圆形的细胞核在微管的作用下沿轴丝延长并在胞质内弯曲, 核和轴丝随着精细胞的纵向伸长而延长, 细胞核最终成为线状; 斑块状的染色质逐渐解体, 呈细小颗粒状和粗颗粒状, 最后浓缩成高密度的均质物; 高尔基体分泌的囊泡不断融合, 形成大小不一的附属小滴前体, 最后融合并延伸成一个纺锤形的附属小滴; 许多小的线粒体不断融合成一个细长的线粒体, 移至核的后端。精子为前部带有附属小滴的长线状, 全长约58.39μm, 可分为顶体、颈部、中段和尾部四部分。长锥形的顶体位于精子最前端, 其后为基体; 颈部由基体产生的“9+2”型轴丝和与之并行的线状核组成; 顶体和颈部两者长共约6.65μm。中部长约42.95μm, 纺锤形的附属小滴(长约9.33μm, 最宽处约2.13μm)紧靠核和轴丝, 其后为颗粒状糖原及一个细长的线粒体; 尾部长约8.79μm, 只有轴丝贯穿。 相似文献
14.
V. A. Kalmykov 《Physical Oceanography》1996,7(5):359-368
The wave-wave kinetic equation for surface gravity waves occurring in a deep sea and a sea of finite depth is solved numerically,
using the Runge-Kutta technique. Spectral evolution was the result only of the waves’ being non-linear, without any contribution
from wave generation and dissipation. The JONSWAP frequency spectra and the angular spectra of various widths were used to
perform calculations. The existence of a steady angular wave spectrum, following its long evolution in a deep sea, has been
confirmed here. For the sea of finite depth, a new result has been obtained. It exhibits the ‘focusing’ of the frequential
and the angular spectra when the wavelength of a harmonic from the spectral maximum equals 2π, of the depth of the sea. With
the depth further decreasing, the wave spectrum swiftly expands. The three-dimensional wave field in a deep sea becomes two-dimensional
in the shallows.
Translated by Vladimir A. Puchkin. 相似文献
15.
Solutions, termed frontal-trapped Rossby waves, have been found for the long-wave equation in a model of a two-layer fluid
with the frontal boundary given in the form of an exponential function. Data from a hydrological survey of a subpolar hydrological
front in the vicinity of Newfoundland are analysed. A frontal-trapped wave model is shown to describe about 40% of the dispersion
of the initial seawater density field.
Translated by V. Puchkin. 相似文献
16.
17.
YU Dingyong XU Delun ZHENG Jianguo
Professor Engineering School Ocean University of Qingdao Qingdao P. R. China
Professor Physical Oceanology Laboratory Ocean University of Qingdao Qingdao P. R. China
Lecturer Engineering School Ocean University of Qingdao Qingdao P. R. China 《中国海洋工程》1999,(4)
Theoretical studies so far on random wave groups have all been in linear ways.Methods to sim-ulate random wave groups,an important subject in ocean engineering,also employ relationship resulting froma Gaussian process.Many filed measurements have shown that the real sea surfase displacement deviatessomewhat from Gaussian distribution.Tayfun et al.have further depicted in theory that the envelope spectralpeak frequency is constantly zero for a Gaussian process which means that the groupiness factors will be con-stants,too.In this paper,the effect of nonlinearity on groupiness of a random wave field is examined via thetheoretical results derived by Tayfun et al.from an expression of amplitude-modulated Stokes waves.Whenthe surface displacement is treated as a non-Gaussian process,it is found that the group height factors GF_1and GF_2 proposed by Zhao et al.and Yu et al.,respectively,depend on a nonlinearity factor as well as aspectrum-bandwidth factor,deferring from the case of a Gaussion process.Compariso 相似文献
18.
At present the mutual influence of tropical cyclones (TCs) has been investigated to a much lesser extent than the cyclones themselves. Most frequently, such investigations are restricted to the study of the influence of the interaction of two TCs on their motion. However, actually, the mutual influence of TCs is much more diverse. For example, each cyclone alters the state of the medium (in particular, decreases the heat store of the upper ocean layer), i.e., affects the subsequent cyclones. Under conditions of a limited energy resource of the medium, cyclones, existing simultaneously, “compete,” to a degree, with each other. These and other similar circumstances have made it practical to consider tropical cyclones and the environment as interdependent elements of a complex open system. This study considers two versions of nonlinear models describing the interaction of TCs with the upper ocean layer and with one another similarly to a number of well-known and verified models of synergetics (interaction of populations, dynamics of optical quantum generators). It is shown that the models reproduce some very important qualitative features of the evolution of TC intensity. 相似文献
19.
海面-地面系统变化影响评价模型是建立在对区域性海面-地面升降运动及其相应的海陆关系演变过程进行数值模拟、虚拟试验及动态监测、预测基础之上的一种未来海面上升影响预估模型,它为抵御未来海面上升对沿海低平区域的潜在威胁,提供可供决策参考的定量化的空间和属性信息。与以往的海面上升影响预估方法相比,设计的模型在GIS软件平台上进行开发,采用菜单式用户界面,可以就预估的海面-地面系统变化所导致的综合影响进行快速的动态评价,并且在评价中考虑了不同土地利用状况的差异性以及经济产值的时空分布差异性。用该模型对太湖流域地区进行了模拟试验,取得了较好的效果。 相似文献
20.
方斑东风螺样品采自福建省南部诏安海域.其卵囊无色透明,叶片状,每个卵囊内有受精卵500～1 600个,卵径为280～308μm.方斑东风螺胚胎发育在卵囊内进行,第一次和第二次卵裂分别为经裂,分裂中有极叶出现.随后其卵裂以螺旋式不等裂方式进行,在胚胎的动物极形成帽状胚盘.其囊胚期胚体开始缓慢转动.在水温为29.0～29.5℃的条件下,产卵后60～63 h其成为早期面盘幼虫.此期以面盘、足、壳的出现为标志.中期面盘幼虫阶段包括囊内的面盘幼虫至出囊后且卵黄尚未消失的浮游幼虫初期阶段.出囊后的幼虫浮游1～2 d后,卵黄囊完全消失成为后期面盘幼虫,心脏搏动频率加快,足变大并伸长.在水温为27.5～28.5℃的条件下,经10～12 d的浮游,后期面盘幼虫转为底栖生活,随后面盘退化、萎缩并完成变态,营爬行生活,贝壳上出现棕褐色斑纹,成为稚螺. 相似文献