共查询到20条相似文献，搜索用时 140 毫秒
1.
本文解释了热带大尺度大气运动速度的分布,从线性化涡度方程和散度方程求出了波速公式,该公式等于罗斯贝波速与含有X和t的谐和函数之和,其周期约3.5天,并证明,此时扰动为正压不稳定,这种现象的产生是经向扰动和纬向扰动相互作用的结果。 相似文献
2.
根据FGGE-ⅡB资料,利用有限区域中准Lagrange坐标的扰动动能方程计算了发生在1979年的两个南海季风低压的扰动动能收支。结果表明,南海季风低压发生发展过程中的扰动动能主要来自气压梯度力在边界作功和扰动动能的水平通量辐合,尤以边界做功制造动能对低压的发展和加强贡献最大。斜压能量转换对低压动能的增加起一定作用,但贡献很小。正压能量转换在低压发生发展阶段主要是损耗扰动动能。 相似文献
3.
秦曾灏 《中国海洋大学学报(自然科学版)》1987,(3)
本文着重研究大地形对正压大气迭加在非均匀纬向基本气流上挑动演变的影响。用WKBJ方法推导了正压扰动的频率和频散关系以及波作用量所满足的方程。当基本流场定常且存在无限长的东西向山脉时,则有波作用量守恒。据此,获得了正压不稳定的必要条件:即在所考察的平面域内至少在某点或某些点上含地形效应的某一物理量等于零,扰动就可能得到发展。对波包动能的倚时变化的讨论得知,在无摩擦正压纬向非均匀基流的情形,地形对扰动动能并无直接影响,即导波和曳波分别在西风急流的南侧和北侧得到加强,并分别在西风急流的北侧和南侧强度减弱。扰动的发展由扰动的结构所决定。导波和曳波的波长缩短总伴同其轴线倾向于东西向相联系,而它们的波长伸长总是与其轴线倾向于南北向同时发生。还指出,正压扰动的加强(或减弱)与波长的伸长(或缩短)不是必然的联系,它的成立是有条件的。 相似文献
4.
基于一套涡分辨模式数据,本文利用一种新的泛函工具—多尺度子空间变换—将孟加拉湾（BOB）海域的环流系统分解到背景流（>96 d）、中尺度（24～96 d）和高频尺度（<24 d）3个子空间,并用正则传输理论探讨了3个尺度子空间之间内在的非线性相互作用。结果表明,BOB西北部边界和斯里兰卡岛东部是BOB海域多尺度相互作用最显著的区域,中部则较弱。前两个区域的背景流大多正压、斜压不稳定,动能和有效位能正则传输主要表现为正向级串;后者则以逆尺度动能级串为主。具体来说,在BOB西北部与斯里兰卡东部,中尺度涡动能（EKE）主要来源于正压能量路径（即背景流动能向EKE传输）,其次来源于斜压能量路径（即背景流有效位能向中尺度有效位能传输,并进一步转换为EKE）。通过这两个能量路径得到的EKE向更高频的扰动传输能量,起到了耗散中尺度涡的作用。不同于此二者,BOB中部海域的EKE和高频尺度动能主要通过斜压路径获得,随后通过逆尺度级串将动能返还给背景流。苏门答腊岛的西北部也是中尺度和高频尺度扰动较强的海域,正压能量路径和斜压能量路径均是该海域扰动能的来源,但以斜压能量路径为主。 相似文献
5.
秦曾灏 《山东海洋学院学报》1987,17(3):1-12
本文着重研究大地形对正压大气迭加在非均匀纬向基本气流七扰动演变的影响。。用WKBJ方法推导了正压扰动的频率和频散关系以及波作用量所满足的方程。当基本流场定常且存在无限长的东西向山脉时，则有波作用量守恒。据此，获得了正压不稳定的必要条件：即在所考察的平面城内至少在某点或某些点上含地形效应的某一物理量等于零，扰动就可能得到发展。对波包动能的倚时变化的讨论得知．在无摩擦正压纬向非均匀基流的情彤．地形对扰动动能并无直接影响．即导波和曳波分别在西风急流的南侧和北侧得到加强，并分别在西风急流的北侧和南侧强度减弱。扰动的发展由扰动的结构所决定。导波和曳波的波长缩短总伴同其轴线倾向r东西向相联系，而它们的波长伸长总是与其轴线倾向于南北向同时发生。还指出，正压扰动的加强或减弱，与波长的伸长(或缩短)不是必然的联系，它的成立是有条件的。 相似文献
6.
将大气和海洋中f-平面上中尺度地形的扰动问题统一起来作为一个地球物理流体力学问题，应用涡度、能量和经圈动量守恒条件，将原来高度非线性方程变成一个二阶椭园型非线性方程，用数值模拟方法分析了大气中的过山运动和海洋中的沿岸上升流，给出了与观测接近的模拟结果以及运动过程对内部物理参数和外界条件的敏感性分析。所提方法可供进一步的动力学分析和数值研究参考。 相似文献
7.
风暴潮增水是风暴潮与天文潮相互作用理论研究的基本内容,也是风暴潮预报中的重要问题。最大余水位的产生机制对于提高预报精度及海岸带防护有着重要意义。为研究全日潮海域风暴潮增水中的全日扰动和半日扰动,对Horsburgh与Wilson的风暴潮余水位模型进行了改进和扩展,建立了包括多个分潮的余水位分解方法并将其应用于防城港站,对台风"启德"和"山神"影响下的潮位过程进行了分析。结果显示,建立的余水位的分解方法对于全日分潮和半日分潮有良好的适用性。由于高频分潮产生机制的复杂性,该方法对高频分潮应用尚需进一步研究。在全日潮的防城港海域,全日扰动与半日扰动具有相同的量级,二者的和约占总增水的15%~19%。台风过程不同,相位变化项和局地变化项对增水的贡献有较大差异。 相似文献
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9.
浅水波的Boussinesq方程组是弱频散的、非线性的,它与Kdv方程有一定联系,但并不等价。本文给出这个方程组的一个孤立波精确解。它含有两个方向传播的孤立波,其一阶近似包括了Kdv方程的精确解,而零阶近似则为波峰处导数不连续的奇异解。 相似文献
10.
11.
左中道 《海洋学报(英文版)》1986,5(2):195-202
The distribution of wind speed in the easterly in the tropics is not uniform. In the part with large curvature, such as lines of trough and ridge, the wind speed is small, while in the part with small curvature, the wind speed is large. In this paper, these phenomena are expounded with gradient wind equation.Considering the distribution of wind speed, we find the wave speed formula from linearized vorticity and divergence equation. The wave speed is equal to the sum of the Rossby wave speed and a harmonic function for x and t. Its period is about 3.5 days. And it is proved that the disturbance is barotropic instability. The results are caused by interaction between meriodional and zonal disturbances. 相似文献
12.
It is expounded in this paper that the wind is weak in a zone of large curvature and strong in the small one in case of large scale stream field in the tropics. The relation between the variation of stream fields and generation of cyclones in tropical disturbance are also studied based on the authors' another paper. 相似文献
13.
Interactions of Mesoscale Eddy and Western Boundary Current: A Reduced-Gravity Numerical Model Study
A reduced-gravity primitive equation eddy resolving model is used to study the interaction of a typhoon-induced eddy and a wind-driven general circulation. A typhoon-induced eddy is characterized by a core with a relative vorticity of the same order as the local Coriolis parameter. This eddy is neutrally stable relative to a disturbance induced by the westward advection of the eddy, due to the planetary β-effect. Hence, its evolution in the open ocean is similar to the classical frontal geostrophic eddy. Within the western boundary flow regime, the eddy is entrained northward by the mean circulation. This northward eddy advection and the mean-vorticity advection due to eddy flow induce another disturbance with a north-south asymmetry into the circular eddy. Together with the zonal asymmetric disturbance, associated with the planetary β-effect, the original circular eddy becomes unstable. The nonlinear eddy-flow interactions in the eastern flank of a western boundary current causes the eddy to deform quickly into an ellipse and lose its waters and energy into the mean circulation. 相似文献
14.
《Ocean Modelling》2010,35(3-4):125-136
This paper seeks to illustrate the point that physical inconsistencies between thermodynamics and dynamics usually introduce nonconservative production/destruction terms in the local total energy balance equation in numerical ocean general circulation models (OGCMs). Such terms potentially give rise to undesirable forces and/or diabatic terms in the momentum and thermodynamic equations, respectively, which could explain some of the observed errors in simulated ocean currents and water masses. In this paper, a theoretical framework is developed to provide a practical method to determine such nonconservative terms, which is illustrated in the context of a relatively simple form of the hydrostatic Boussinesq primitive equation used in early versions of OGCMs, for which at least four main potential sources of energy nonconservation are identified; they arise from: (1) the “hanging” kinetic energy dissipation term; (2) assuming potential or conservative temperature to be a conservative quantity; (3) the interaction of the Boussinesq approximation with the parameterizations of turbulent mixing of temperature and salinity; (4) some adiabatic compressibility effects due to the Boussinesq approximation. In practice, OGCMs also possess spurious numerical energy sources and sinks, but they are not explicitly addressed here.Apart from (1), the identified nonconservative energy sources/sinks are not sign definite, allowing for possible widespread cancellation when integrated globally. Locally, however, these terms may be of the same order of magnitude as actual energy conversion terms thought to occur in the oceans. Although the actual impact of these nonconservative energy terms on the overall accuracy and physical realism of the oceans is difficult to ascertain, an important issue is whether they could impact on transient simulations, and on the transition toward different circulation regimes associated with a significant reorganization of the different energy reservoirs. Some possible solutions for improvement are examined. It is thus found that the term (2) can be substantially reduced by at least one order of magnitude by using conservative temperature instead of potential temperature. Using the anelastic approximation, however, which was initially thought as a possible way to greatly improve the accuracy of the energy budget, would only marginally reduce the term (4) with no impact on the terms (1), (2) and (3). 相似文献
15.
Alternating zonal flows in an idealized wind-driven double-gyre ocean circulation have been investigated using a two-layer
shallow-water eddy-permitting numerical model. While the alternating zonal flows are found almost everywhere in the time-mean
zonal velocity field, their meridional scales differ from region to region. In the subpolar western boundary region, where
the energetic eddy activity induces quasi two-dimensional turbulence, the alternating zonal flows are generated by the inverse
energy cascade and its arrest by Rossby waves, and the meridional scale of the flows corresponds well to the Rhines scale.
In the eastern part of the basin, where barotropic basin modes are dominant, the zonal structure is formed through the nonlinear
effect of the basin modes and is wider than the Rhines scale. Both effects are likely to form zonal structure between the
two regions. These results show that Rossby basin modes become an important factor in the formation of alternating zonal flows
in a closed basin in addition to the arrest of the inverse energy cascade by Rossby waves. The wind-driven general circulation
associated with eddy activities plays an essential role in determining which mechanism of the alternating zonal flows is possible
in each region. 相似文献
16.
Impact of the central Pacific zonal wind divergence and convergence on the central Pacific El Nio event 总被引：1，自引：1，他引：0
The central Pacific(CP) zonal wind divergence and convergence indices are defined, and the forming mechanism of CP El Nio(La Nia) events is discussed preliminarily. The results show that the divergence and convergence of the zonal wind anomaly(ZWA) are the key process in the forming of CP El Nio(La Nia) events. A correlation analysis between the central Pacific zonal wind divergence and convergence indices and central Pacific El Nio indices indicates that there is a remarkable lag correlation between them. The central Pacific zonal wind divergence and convergence indices can be used to predict the CP events. Based on these results, a linear regression equation is obtained to predict the CP El Nio(La Nia) events 5 months ahead. 相似文献
17.
本文将非线性热力学理论应用到大尺度海洋系统,找到了一个适合于描述海温扰动发展的热力学判据。计算表明:这种热力学判据能够较好地报出海温异常事件,估计海温异常的强弱。本文还利用这种热力学判据分析了海洋与大气之间的热交换和平流效应对海温扰动演化的影响。 相似文献
18.
Effects of different types of mechanical disturbances on a charophyte dominated macrophyte community
Charophytes are unique and endangered macroalgae. Mechanical stress is known to damage charophyte communities, however, virtually nothing is known how such disturbance affect seasonal succession and recovery of charophyte communities. We examined the response of a shallow water charophyte community to different types and timing of disturbances by conducting seasonal in situ field experiment in a brackish water ecosystem. The disturbances associated with mechanical removal of vegetation or sediment had the largest impact on the charophyte community. Disturbances that only partly damaged the plants had minor effects and communities were characterized by fast recovery. The timing of disturbance had significant effects on the charophyte community with stronger effects when disturbed at the early stage compared to mid-stage of seasonal succession. 相似文献
19.
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
20.
Wu Dexing 《海洋学报(英文版)》1994,13(4):465-474
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