共查询到18条相似文献，搜索用时 729 毫秒
1.
2.
程鹏 《海洋学报(英文版)》2020,42(5):1-2
在受波动影响的近岸浅水区域，运用sigma坐标是计算平均水位附近的余流的有效途径。本项研究在理论上分析了在狭窄潮汐水道中sigma坐标下的余流的物理意义，并运用一系列的理想化数值模型对分析结果进行了验证。对于浅水波，sigma层和水体中的波动面相一致，因而斯托克斯速度及其分量可以用sigma坐标上的速度来表达。一个sigma层上的余流（即sigma余流）是位于这一sigma层平均深度上的欧拉余流和斯托克斯速度垂向分量的和，可以被看做是半拉格朗日余流。因为斯托克斯速度的垂向分量比其水平分量小一个量级，sigma余流可看做为欧拉余流的近似。在sigma层上的物质输运余流是sigma余流和斯托克斯速度水平分量的和，在大小和方向上和拉格朗日余流近似。 相似文献
3.
磨刀门口夏冬季沿岸流特征及成因分析 总被引：1，自引：0，他引：1
根据2011—2012年磨刀门口的夏、冬季大、中、小潮定点观测资料,对欧拉余流、斯托克斯余流以及拉格朗日余流进行分析。结果表明:（1）外海测点的欧拉余流和拉格朗日余流,冬季在各潮型下均为一致的西南沿岸方向,夏季除东、西汊道点在强径流下表现为顺汊道指向外海方向,其余外海各点仍以西南沿岸方向为主;（2）斯托克斯余流远小于欧拉余流,夏季明显大于冬季,方向基本与欧拉余流相反;（3）冬季磨刀门口海域具有稳定西南向沿岸流特征,南海东北季风的驱动作用是其形成的主要原因;夏季磨刀门口各潮型下沿岸流特征各异,其影响的主要因素为径流和风,同时地形的影响不可忽略,特别是拦门沙形成的汊道分流作用,对强径流作用下水沙输移影响十分显著。 相似文献
4.
利用MITgcm数值模式,研究了单海脊地形下的内潮致拉格朗日余流,发现余流结构与内潮结构相对应,从海脊附近沿波射线分布,向东、西两方向流动。与欧拉余流相比,拉格朗日余流在海脊附近呈现辐散的特征,欧拉余流则表现为辐聚的特征。改变地形、正压潮流速等参数,拉格朗日余流结构随之变化。当海脊变宽时,余流随波射线的消失而变得很小且混乱;当海脊变高时,海脊附近逐渐产生向海底方向的流动,与海面反射的余流形成平行的射线,余流整体增强,海脊附近的余流在向外流动过程中增幅减小;当正压潮流速增大时,余流结构基本不变,但在高窄海脊地形下海脊附近的平行射线会逐渐合为一支从海脊顶部产生的流动。 相似文献
5.
多年现场观测揭示,在大洋深层许多区域存在出人意料的高能区,诸如在赤道1000～3000m深度间存在着东西流向随深度交替变化的急流,本文提出连系不同密度水体输运的局部浮力振荡所产生的波动以及关连的能量辐射和沿赤道产生的局部能量辐聚是形成赤道深层急流的主要动力机制.本文结果还揭示,铅垂向湍粘系数和湍扩散系数的大小与赤道深层急流的结构和强度间存在密切的关系.对应大的铅垂向湍粘系数和湍扩散系数,急流强度减弱且其纬向相干尺度和铅垂尺度增大.另外不同周期的浮力振荡产生不同结构和强度的急流.振荡周期越长,急流的核心位置离东边界越远、沿赤道的相干尺度也越大. 相似文献
6.
利用热带海洋和全球大气试验(TOGA)期间(1980～1996年)热带大气海洋观测阵(TAO)的长期浮标资料,分析了赤道行星波对西赤道太平洋暖池热传播的作用。结果表明,西赤道太平洋暖池纬向热传播主要出现在次表层水体中,并沿温跃层向东传播;而向西传播的季节热结构变化主要出现在中、西赤道太平洋的混合层中;驻波型传播在西赤道太平洋主要出现于温跃层,在中赤道太平洋主要出现于混合层和温跃层,在东赤道太平洋主要出现于混合层。在平均条件下,赤道太平洋上层水温纬向热传播信号以驻波型和东传型较强,西传型较弱。赤道Kelvin波压力分量贯穿西、东赤道太平洋并向东输送暖池热能,纬向流分量的热输送主要出现在西赤道太平洋;Rossby波压力分量的热输送主要出现在东、中赤道太平洋;混合Rossby重力波激发纬向流的热输送作用比相应温跃层扰动强。在平均条件下,赤道太平洋上层水温的驻波型变化制约了西赤道太平洋暖池热量的持续向东输送,因此形成了赤道太平洋水温的正常季节变化形态。当水温的驻波型变化减弱而东传型变化加强时,随后将形成厄尔尼诺现象。 相似文献
7.
基于SODA再分析资料和TAO资料,利用EOF和统计分析等方法,分别研究了赤道太平洋海面纬向风应力异常和赤道太平洋上层纬向流异常的时空特征及其对西太平洋暖池纬向运移的影响。结果显示,赤道太平洋海面纬向风应力距平场第一模态具有2—5年的年际变化特征,其时空分布呈东、西向的反位相变化;而赤道太平洋上层纬向流距平场的第一模态则为1—2年的年和年际变化,且整个研究区域位相统一。纬向风应力和纬向流异常变化最显著的区域都在赤道中太平洋。相关分析显示,赤道中太平洋海面纬向风应力异常和赤道西太平洋上层纬向流异常分别对西太平洋暖池纬向运移有约2个月和4—6个月的超前影响,是暖池纬向运移的两个重要动力因素。回归分析表明,赤道中太平洋海面纬向风应力异常和赤道西太平洋上层纬向流异常对西太平洋暖池纬向运移有很好的预报意义。 相似文献
8.
根据辐射沙洲邻近主水道和中心沙洲滩面水道33个站次的准同步实测潮流资料, 计算了各站位垂线平均欧拉余流、斯托克斯余流、拉格朗日余流, 并分别进行了逐站位的分析和比较.各站位斯托克斯余流相对较小, 在水道口门处斯托克斯余流较大, 余流流向大都沿涨潮流向, 豆腐渣腰门水道及其以东站位的斯托克斯余流则大致沿落潮流向.欧拉余流和拉格朗日余流大小和流向基本一致.研究海域存在着半封闭的顺时针方向的海水净输移.西洋水道和条鱼港水道是辐射沙洲中心腹地的净进水通道, 而豆腐渣腰门水道、陈家坞槽水道、外王家槽水道、苦水洋海域水道则是净出水通道. 相似文献
9.
基于2017年春季和冬季的海流资料分析了红海湾海区海流特征、潮流状况、涨落潮流特性、余流特征及表层漂流特征。研究海域共布设3个临时潮位观测站和11个全潮水文观测站。根据流速、流向过程曲线和潮位过程曲线的关系，得出涨(落)潮流速最大的时刻和最小流速发生时刻与潮位关系并非固定在高(低)潮时或半潮面左右，由此看出，研究海域的潮波介于驻波与前进波之间，属于不规则半日潮流主导的海域。研究海域中大部分站位潮流属于往复流，少数站位潮流运动具有一定的旋转性，平均涨潮流速最大为7 cm/s，平均退潮流速最大为14 cm/s。春季大潮期和中潮期各站余流流向整体为偏东向，小潮期，除少数测站余流流向偏向南东向，其余测站余流流向偏西向；冬季大潮期和中潮期各站余流流向整体为偏西向，小潮期，湾西侧余流流向偏西向，湾东侧余流流向偏南东向。垂向上各层余流流速由表至底逐渐减小，流向基本一致。 相似文献
10.
《海洋预报》2017,(5)
采用无界理想海洋线性扰动模型,对赤道海洋Kelvin波在纬向风场异常强迫下的响应即强迫赤道海洋Kelvin波的异常做了解析求解,主要结果如下:该强迫赤道海洋Kelvin波的频率、波长和波速都与外强迫风场的相同,在赤道纬向流振幅最大并随纬度增加衰减,该风场越强,该强迫赤道海洋Kelvin波也越强,两者呈正比关系。当该风场频率和范围确定后,则该强迫赤道海洋Kelvin波被限制在一定平均水深范围内;该风场的频率越高、纬向波长越长、随纬度增加衰减越小,则该水深就越大。在所取参数下,该风场异常与该强迫赤道海洋Kelvin波流场异常的位相基本相同。在西风强迫下有东向流,反之亦然;强迫赤道海洋Kelvin波的流场与位势场则完全同位相,东向流对应于正位势,反之亦然,这也是经典Kelvin波的配置。该强迫赤道海洋Kelvin波与经典Kelvin波的不同在于:前者是频散的强迫波动,并被限制在一定水深中;后者是自由波动。将该强迫Kelvin波的解析解与热带印度洋和太平洋的实况以及诊断进行对比后知,两者总体看来一致,实际热带大洋中该强迫赤道海洋Kelvin波应确实存在。 相似文献
11.
Equatorially trapped Rossby waves in the presence of meridionally sheared baroclinic flow in the Pacific Ocean 总被引：1，自引：0，他引：1
TOPEX/POSEIDON altimeter data are analyzed for the 8.5-year period November 1992 to May 2001 to investigate the sea surface height (SSH) and geostrophic velocity signatures of quasi-annual equatorially trapped Rossby waves in the Pacific. The latitudinal structures of SSH and both components of geostrophic velocity are found to be asymmetric about the equator across the entire Pacific with larger amplitude north of the equator. The westward phase speeds are estimated by several different methods to be in the range 0.5-0.6 m s−1. These observed characteristics are inconsistent with the classical theory for first vertical, first meridional mode equatorially trapped Rossby waves, which predicts a phase speed of about 0.9 m s−1 with latitudinally symmetric structures of SSH and zonal velocity and antisymmetric structure of meridional velocity. The observations are even less consistent with the latitudinal structures of SSH and geostrophic velocity components for other modes of the classical theory.The latitudinal asymmetries deduced here have also been consistently observed in past analyses of subsurface thermal data and altimeter data and have been variously attributed to sampling errors in the observational data, a superposition of multiple meridional Rossby wave modes, asymmetric forcing by the wind, and forcing by cross-equatorial southerly winds in the eastern Pacific. We propose a different mechanism to account for the observed asymmetric latitudinal structure of low-frequency equatorial Rossby waves. From the free-wave solutions of a simple 1.5-layer model, it is shown that meridional shears in the mean equatorial current system significantly alter the potential vorticity gradient in the central and eastern tropical Pacific. The observed asymmetric structures of sea surface height and geostrophic velocity components are found to be a natural consequence of the shear modification of the potential vorticity gradient. The mean currents also reduce the predicted westward phase speed of first meridional mode Rossby waves, improving consistency with the observations. 相似文献
12.
The seasonal variation of undercurrent and temperature in the equatorial Pacific jointly derived from buoy measurement and assimilation analysis 总被引：3，自引：2，他引：1
Based on the TOGA-TAO buoy chain observed data in the equatorial Pacific and the assimilation analysis results from SODA(simple ocean data assimilation analysis), the role of the meridional cells in the subsurface of the tropical Pacific was discussed. It was found that, the seasonal varying direction of EUC (the quatorial Undercurrent)in the Peacific is westwards beginning from the eastern equatorial Pacific in the boreal spring. The meridional cell south of the equator plays important role on this seasonal change of EUC.On the other hand, although the varying direction is westwards,the seasonal variation of temperature in the same region gets its minimum values in the boreal autumn beginning from the eastern equatorial Pacific.The meridional cell north of the equator is most responsible for the seasonal temperature variation in the eastern equatorial Pacific while the meridional cell south of the equator mainly controls the seasonal temperature change in the central Pacific. It is probably true that the asymmetry by the equator is an important factor influencing the seasonal cycle of EUC and temperature in the tropical Pacific. 相似文献
13.
Effects of adjusting vertical resolution on the eastern equatorial Pacific cold tongue 总被引：3，自引：0，他引：3
The vertical resolution of LICOM1.0 (LASG/IAP Climate System Ocean Model, version 1.0) is adjusted by increasing the level amount within the upper 150 m while keeping the total of levels. It is found that the eastern equatorial Pacific cold tongue is sensitive to the adjustment. Compared with the simulation of the original level scheme, the adjusting yields a more realistic strucature of cold tongue extending from the coast of Peru to the equator, as well as a temperature minimum at Costa Rica coast, north of the cold tongue. In the original scheme experiment, the sharp heating by net surface heat flux at the beginning of spin-up leads to a great warming in the eastern equatorial Pacific Ocean. The weak vertical advection due to a too thick mixed layer in the coarse vertical structure also accounts for the warm bias. The fact that most significant improvements of the upper 50 m temperature appear at the region of the thinnest mixed layer indicates the necessity of fine vertical resolution for the eastern equatorial Pacific Ocean. However, the westward extension of equatorial cold tongue, a defect in the original scheme, gets even more serious in the adjusting scheme due to the intensified vertical velocity and hence vertical advection in the central-eastern equatorial Pacific Ocean. 相似文献
14.
Takashi Setoh Shiro Imawaki Alexander Ostrovskii Shin-Ichiro Umatani 《Journal of Oceanography》1999,55(3):385-394
Interdecadal variations of El Niño/Southern Oscillation (ENSO) signals and annual cycles appearing in the sea surface temperature (SST) and zonal wind in the equatorial Pacific during 1950–1997 are studied by wavelet, empirical orthogonal function (EOF) and singular value decomposition (SVD) analyses. The typical timescale of ENSO is estimated to be about 40 months before the late 1970s and 48–52 months after that; the timescale increased by about 10 months. The spatial pattern of the ENSO signal appearing in SST also changed in the 1970s; before that, the area of strong signal spread over the extratropical regions, while it is confined near the equator after that. The center of the strongest signal shifted from the central and eastern equatorial Pacific to the South American coast at that time. These SST fluctuations near the equator are associated with fluctuations of zonal wiond, whose spatial pattern also shifted considerably eastward at that time. In the eastern equatorial Pacific, amplitudes of annual cycles of SST are weak in El Niño years and strong in La Niña years. This relation is not clear, however, in the 1980s and 1990s. 相似文献
15.
16.
ENSO variability and the eastern tropical Pacific: A review 总被引：3，自引：0，他引：3
El Niño-Southern Oscillation (ENSO) encompasses variability in both the eastern and western tropical Pacific. During the warm phase of ENSO, the eastern tropical Pacific is characterized by equatorial positive sea surface temperature (SST) and negative sea level pressure (SLP) anomalies, while the western tropical Pacific is marked by off-equatorial negative SST and positive SLP anomalies. Corresponding to this distribution are equatorial westerly wind anomalies in the central Pacific and equatorial easterly wind anomalies in the far western Pacific. Occurrence of ENSO has been explained as either a self-sustained, naturally oscillatory mode of the coupled ocean–atmosphere system or a stable mode triggered by stochastic forcing. Whatever the case, ENSO involves the positive ocean–atmosphere feedback hypothesized by Bjerknes. After an El Niño reaches its mature phase, negative feedbacks are required to terminate growth of the mature El Niño anomalies in the central and eastern Pacific. Four requisite negative feedbacks have been proposed: reflected Kelvin waves at the ocean western boundary, a discharge process due to Sverdrup transport, western Pacific wind-forced Kelvin waves, and anomalous zonal advections. These negative feedbacks may work together for terminating El Niño, with their relative importance being time-dependent.ENSO variability is most pronounced along the equator and the coast of Ecuador and Peru. However, the eastern tropical Pacific also includes a warm pool north of the equator where important variability occurs. Seasonally, ocean advection seems to play an important role for SST variations of the eastern Pacific warm pool. Interannual variability in the eastern Pacific warm pool may be largely due to a direct oceanic connection with the ENSO variability at the equator. Variations in temperature, stratification, insolation, and productivity associated with ENSO have implications for phytoplankton productivity and for fish, birds, and other organisms in the region. Long-term changes in ENSO variability may be occurring and are briefly discussed. This paper is part of a comprehensive review of the oceanography of the eastern tropical Pacific. 相似文献
17.
The long-term trend of the sea surface wind speed and the wave height (wind wave, swell, mixed wave)in global ocean during the last 44 a 总被引：2，自引：1，他引：1
Utilizing the 45 a European Centre for Medium-Range Weather Forecasts(ECMWF)reanalysis wave data(ERA-40),the long-term trend of the sea surface wind speed and(wind wave,swell,mixed wave)wave height in the global ocean at grid point 1.5×1.5 during the last 44 a is analyzed.It is discovered that a majority of global ocean swell wave height exhibits a significant linear increasing trend(2–8 cm/decade),the distribution of annual linear trend of the significant wave height(SWH)has good consistency with that of the swell wave height.The sea surface wind speed shows an annually linear increasing trend mainly concentrated in the most waters of Southern Hemisphere westerlies,high latitude of the North Pacific,Indian Ocean north of 30 S,the waters near the western equatorial Pacific and low latitudes of the Atlantic waters,and the annually linear decreasing mainly in central and eastern equator of the Pacific,Juan.Fernandez Archipelago,the waters near South Georgia Island in the Atlantic waters.The linear variational distribution characteristic of the wind wave height is similar to that of the sea surface wind speed.Another find is that the swell is dominant in the mixed wave,the swell index in the central ocean is generally greater than that in the offshore,and the swell index in the eastern ocean coast is greater than that in the western ocean inshore,and in year-round hemisphere westerlies the swell index is relatively low. 相似文献
18.
有界赤道大洋波包解及其年际年代际变率 总被引：1，自引：0，他引：1
Linearized shallow water perturbation equations with approximation in an equatorial β plane are used to obtain the analytical solution of wave packet anomalies in the upper bounded equatorial ocean. The main results are as follows. The wave packet is a superposition of eastward travelling Kelvin waves and westward travelling Rossby waves with the slowest speed, and satisfies the boundary conditions of eastern and western coasts, respectively.The decay coefficient of this solution to the north and south sides of the equator is inversely proportional only to the phase velocity of Kelvin waves in the upper water. The oscillation frequency of the wave packet, which is also the natural frequency of the ocean, is proportional to its mode number and the phase velocity of Kelvin waves and is inversely proportional to the length of the equatorial ocean in the east-west direction. The flow anomalies of the wave packet of Mode 1 most of the time appear as zonal flows with the same direction. They reach the maximum at the center of the equatorial ocean and decay rapidly away from the equator, manifested as equatorially trapped waves. The flow anomalies of the wave packet of Mode 2 appear as the zonal flows with the same direction most of the time in half of the ocean, and are always 0 at the center of the entire ocean which indicates stagnation, while decaying away from the equator with the same speed as that of Mode 1. The spatial structure and oscillation period of the wave packet solution of Mode 1 and Mode 2 are consistent with the changing periods of the surface spatial field and time coefficient of the first and second modes of complex empirical orthogonal function(EOF)analysis of flow anomalies in the actual equatorial ocean. This indicates that the solution does exist in the real ocean, and that El Ni?o-Southern Oscillation(ENSO) and Indian Ocean dipole(IOD) are both related to Mode 2.After considering the Indonesian throughflow, we can obtain the length of bounded equatorial ocean by taking the sum of that of the tropical Indian Ocean and the tropical Pacific Ocean, thus this wave packet can also explain the decadal variability(about 20 a) of the equatorial Pacific and Indian Oceans. 相似文献