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1.
利用一个两层半的热带海洋模式,采用数值实验的方法研究了热带海洋对于初始海洋混合层深度异常和大气季节内时间尺度热力强迫激发产生的Ｒｏｓｓｂｙ波和Ｋｅｌｖｉｎ波。研究表明,初始海洋混合层深度异常和大气热力强迫,可以在两层半热带海洋模式中激发产生东向传播具有Ｋｅｌｖｉｎ波性质的波动和具有Ｒｏｓｓｂｙ波性质的波动。热力强迫激发产生海洋Ｒｏｓｓｂｙ波和Ｋｅｌｖｉｎ波所需时间长于初始海洋混合层深度异常和大气季节内动力强迫激发产生两波所需时间,与大气季节内动力强迫激发的Ｒｏｓｓｂｙ波相比,初始深度异常与大气热力强迫激发产生Ｒｏｓｓｂｙ波具有不同的热力性质。 相似文献
2.
试图建立一个简单海气耦合模式,其中大气垂直分为两层,为－β平面近似线性模式。在非绝热加热项中包含了对流凝结潜热与大尺度流场之间相互作用的ＣＩＳＫ机制以及蒸发、感热与扰动风场之间的反馈机制,并考虑了东风区与西风区的不同。由于只研究大气的平均纬向运动,故模式大气中仅含有Ｋｅｌｖｉｎ波。海洋模式为一约化重力模式,只保留了Ｒｏｓｓｂｙ波。对这一海气耦合模式进行特征波动分析,发现考虑海气耦合效应并不影响大气波动的性质,在东风区大气Ｋｅｌｖｉｎ波仍然增幅和东传;在西风区大气Ｋｅｌｖｉｎ波振幅衰减。但海气耦合效应却使得大气Ｋｅｌｖｉｎ波的传播速度减慢,周期增大。当考虑海气耦合效应时,海洋Ｒｏｓｓｂｙ波的稳定性质发生变化,由原来的中性波动变为非中性波动。在西风区,波数小于某临界波数的长Ｒｏｓｓｂｙ波振幅增大,而短的Ｒｏｓｓｂｙ波振幅衰减。在东风区结论相反。对海气耦合模式中波动的分析,为数值模拟西太平洋暖池的形成及其对大气扰动的影响建立了理论基础。 相似文献
3.
气候平均风场作用下热带太平洋主流系和赤道行星波研究 总被引：2，自引：1，他引：1
将两层约化重力原始流体动力方程耦合气候月平均风场,数值计算流场基本能够正反反映带太平洋上层主流系和温跃层的空间分布和季节变化,在气候平均条件下,东太平洋１２５°Ｗ附近经向风应力可激发出高阶混合Ｒｏｓｓｂｙ重力波,海洋高阶赤道Ｋｅｌｖｉｎ波流速模态可从西太平洋边界传播到东太平洋边界,而高阶赤道Ｋｅｌｖｉｎ波温跃层模态从西太平洋边界东传后,在中太平洋肥到高阶混合Ｒｏｓｓｂｙ重力波诱发的西传温跃层扰动的 相似文献
4.
利用美国国家气象中心的综合性大气-海洋资料序列(COADs),采用三种海气耦合模式对海洋挟卷速度的表达方法,计算了实测资料影响下模式挟卷速度的分布特征。利用求得的挟卷速度和由资料序列求得的热量通量分布,采用Niiler—Kraus一维混合层SST预报模式,估计了各种模式扶卷作用对SST的影响。通过比较各个模式的计算结果,提出: 1.挟卷作用是影响SST变化分布的一个重要因子。挟卷速度的分市取决于所采用参数化形式中主要影响因素的分布情况。不考虑平流作用时,模式SST的分布也取决于挟卷参数化形式中主要影响因素的分布。2.由海气耦合不稳定模态的分析得出三个模式对不稳定海气耦合波影响的特征。 相似文献
5.
用第一部分建立的简单海气耦合模式,研究了西太平洋暖池的形成过程及其对大气扰动的影响。模式可以较好地模拟出热带太平洋海温“西高东低”的分布,以及“暖池”附近ＳＳＴ的水平梯度较小等特征。在垂直方向上海洋混合层深度关于赤道呈准对称的“马鞍”型分布特征也可以从理论上和数值模拟的结果中得到证实。模式中“暖池”形成的时间尺度大约为半年多,大气中凝结潜热的释放有利于“暖池”的快速形成,提高凝结潜热的释放的效率,“暖池”形成的时间就缩短。“暖池”形成的动力学机制是海气耦合系统中海洋Ｒｏｓｓｂｙ波振幅的不稳定增长所致。“暖池”区海气之间的耦合作用确实对热带大气的季节内振荡产生影响。当海气之间进行耦合作用时,可以模拟得到扰动传播的周期大约为５０多天（ｄ）,与实际观测相吻合。提高海气之间的耦合强度会降低扰动的传播速度,使传播周期明显加大。当不考虑海气之间的耦合作用时,模拟得到的扰动传播周期明显地比用耦合模式得到的要小。 相似文献
6.
7.
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
8.
《中国海洋大学学报(自然科学版)》2017,(7)
2014年4月12日,中国海洋大学东方红2号调查船在黑潮延伸体海区由暖水侧向北穿越海洋锋时,捕捉到了一次层积云云底和云顶高度升高的过程。本文利用船测数据结合WRF模式进行数值模拟和试验,对此次层积云迅速发展的机理进行了综合分析。结果显示,在黑潮延伸体区域,西北风控制下,海洋锋和来自日本本州岛陆地的低空暖平流共同作用使得层积云发展。通过数值试验发现,海洋锋作为背景场,为该区域提供了200W·m~(-2)的潜热通量并导致气压下降,从而在暖水侧产生了0.05m·s~(-1)的上升运动。同时,来自日本本州岛陆地的暖平流作为日尺度扰动,在09-12UTC到达潜热通量中心,导致该时段该区域2~3℃的增温和0.5hPa的降压。但两者并非单纯线性叠加,而是在海洋锋提供背景条件的前提下,暖平流产生触发作用,通过局地海气相互作用,使得该时段该区域垂直运动异常增强,进而造成云的异常发展。本研究有助于理解在复杂大气背景扰动扰动下MABL对海洋强迫的响应机理,同时对于理解海洋对边界层的影响又反馈到海洋的过程有一定帮助。 相似文献
9.
赤道太平洋低频波动的某些特征 总被引：1，自引：0，他引：1
利用赤道附近南北纬１０度之间２２个站的水位观测资料和位于１４０°Ｗ浮标站的海流资料,分析了热带太平洋赤道区域低频波动的特征,发现季节内时间尺度的变化在赤道海区是一个普遍的现象。热带西太平洋海区上层海洋季节内时间尺度的变化可由具有东传性质的Ｋｅｌｖｉｎ斜压模态的波动和具有西传性质的Ｒｏｓｓｂｙ斜压模态的传播所引起,在赤道上,东向传播的波速约为２．７ｍ／ｓ,在赤道以北,西向传播的波速约为１．６ｍ／ｓ。在赤道东太平洋２５０ｍ的深度上,可以发现西太平洋低频变化对该处流速的影响,从西太平洋传播到东太平洋的平均速度大约１．３ｍ／ｓ。中太平洋低频变化具有驻波的特征,１９８６～１９８７ＥｌＮｉｎｏ事件的发生与这种驻波振荡有关。 相似文献
10.
北太平洋副热带模态水形成区混合层热动力过程诊断分析 总被引：2，自引：0，他引：2
利用NCEP海洋数据和COADS海气通量资料,通过诊断分析,揭示了海表热力强迫、垂直夹卷、埃克曼平流和地转平流效应在北太平洋副热带模态水形成过程中的贡献。研究表明,在北太平洋副热带3个模态水形成海域冬季混合层降温过程中,海表热力强迫和垂直夹卷效应是主导因素,二者的相对贡献分别约为67%和19%(西部模态水)、53%和21%(中部模态水)、65%和30%(东部模态水);并且在东部模态水形成海域,埃克曼平流和地转平流皆是暖平流效应,而在西部和中部模态水形成海域,仅有地转平流是暖平流效应。进一步的分析表明,海洋平流(地转平流、埃克曼平流)对北太平洋副热带模态水形成海域秋、冬季混合层温度的年际、年代际异常有显著影响,在西部模态水形成海域,海表热力强迫(62%)和地转平流(32%)是导致混合层温度年际、年代际变化的主要因子;在中部模态水形成海域,混合层温度的年际、年代际变化是埃克曼平流(32%)、地转平流(30%)和海表热力强迫(25%)共同作用的结果;相对而言,东部模态水形成海域混合层温度的年际、年代际异常主要受海表热力强迫(67%)控制。 相似文献
11.
The instability of long-wave disturbances of a geostrophic current with linear velocity shear is studied with allowance for the diffusion of buoyancy. A detailed derivation of the model problem in dimensionless variables is presented, which is used for analyzing the dynamics of disturbances in a vertically bounded layer and for describing the formation of large-scale intrusions in the Arctic basin. The problem is solved numerically based on a high-precision method developed for solving fourth-order differential equations. It is established that there is an eigenvalue in the spectrum of eigenvalues that corresponds to unstable (growing with time) disturbances, which are characterized by a phase velocity exceeding the maximum velocity of the geostrophic flow. A discussion is presented to explain some features of the instability. 相似文献
12.
The baroclinic instability of the Bosphorus currents is studied in terms of minor disturbances. The Bosphorus current and
undercurrent depend on the seasonal variability of the strait’s dynamics manifesting itself in the intensification of flows
and in the modification of their configuration. In the frame of the linear statement of the problem, the spatial and temporal
characteristics of the disturbances have been obtained for different velocities, layer thicknesses, and interface depths,
as well as for water stratifications. Some regularities in the development of instability in the Bosphorus Strait have been
identified.
Translated by Vladimir A. Puchkin. 相似文献
13.
An analytical study of the influence of three-wave resonant interactions on the evolution of unstable wave disturbances is
presented in the Kelvin-Helmholtz model. These results may be of interest in analyzing the dynamics of disturbances at the
ocean-atmosphere interface and in two-layer flows which arise in the ocean and are characterized by large gradients of flow
velocity at the boundary of layers. In the case under consideration, the instability arises when eigenfrequencies coincide
in the framework of a single mode and the instability is algebraic. The amplitudes of the two other interacting stable waves
are assumed to be small compared to the amplitude of the third, unstable, mode. The system of amplitude equations for this
case is investigated using the WKB method. As a result, we obtain the formulas coupling the solutions for the time before
and after a transition through a singular point, where the amplitude of the linearly unstable wave has a local minimum. These
formulas give the rule of transformation of the parameter that characterizes a phase shift between fast and slow modes and
determines the behavior of the system. It is shown that, in a transition through a singular point, this parameter changes
randomly. As long as the parameter is positive, the amplitude of the linearly unstable wave remains limited and oscillates
stochastically. In a transition of the parameter through zero, we exit the stabilization region and have an infinite growth
of amplitude. The transition into the instability region is random. However, if the time interval where the amplitude remains
limited is large enough, the scenario of the behavior of the system we have obtained can be treated as the partial stabilization
of instability. The results make it possible for us to investigate the stochasticity caused by the nonlinear interaction of
gravity-capillary waves in a two-layer model of a shear flow. These results are also of interest in analyzing secondary flows
in laboratory facilities modeling the ocean and atmospheric processes. 相似文献
14.
V. V. Lyahov 《Izvestiya Atmospheric and Oceanic Physics》2007,43(3):308-316
The effect of a real departure of the atmosphere from the adiabaticity condition on the generation and dissipation of acoustic-gravity waves (AGWs) throughout the entire height of the atmosphere up to the mesopause (≈90 km) is studied. The results of solving the derived dispersion equation can be helpful in the formation of boundary conditions during simulation of the propagation of wave disturbances in the thermosphere and above. Unlike an adiabatic model, in a nonadiabatic model of the atmosphere, the frequencies (the roots of the dispersion equation) are complex and waves attenuate in some atmospheric layers, whereas other layers are unstable with respect to the onset of the corresponding AGW modes. As the height increases, the phase velocities of both acoustic and gravity branches of AGWs decrease and dissipation is enhanced. It is shown that macroscopic flows, along with periodic disturbances, are generated in a nonadiabatic atmosphere. 相似文献
15.
Mesoscale eddies, particularly anticyclonic ones, are dominant features in the Kuril Basin of the Okhotsk Sea. In 1999, both surface drifter and hydrographic observations caught the same anticyclonic eddy northwest of Bussol’ Strait, which has a diameter of ∼100 km, typical surface velocity of 0.2–0.3 m s−1, and less dense core extending to a depth of ∼1200 m. Based on an idea that the generation of mesoscale eddies is caused by strong tidal mixing in and around Kuril Straits, we have conducted a series of three-dimensional numerical model experiments, in which strong tidal mixing is simply parameterized by increasing coefficients of vertical eddy viscosity and diffusivity along the eastern boundary. Initially, a regular series of disturbances with a wavelength of ∼70 km starts to develop. The disturbances can be clearly explained by a linear instability theory and regarded as the baroclinic instability associated with the near-surface front formed in the region between the enhanced mixing and offshore regions. In the mature phase, the disturbances grow large enough that some eddies pinch off and advect offshore (westward), with the scale of disturbances increasing gradually. Typical eddy scale and its westward propagation speed are ∼100 km and ∼0.6 km day−1, respectively, which are consistent with the observations by satellites. The westward propagation can be explained partly due to nonlinear effect of self-offshore advection and partly due to the β-effect. With the inclusion of the upper ocean restoring, the dominance of anticyclonic eddy, extending from surface to a depth of ∼1200 m, can be reproduced. 相似文献
16.
We describe the space-and-time structure of large-scale thermal anomalies in the upper layer in the tropical zone of the Indian
Ocean and study the mechanism of their formation. It is shown that the critical layer in which the phase velocities of propagation
of disturbances coincide with the mean velocity of the zonal current can be formed in the central part of equatorial zone
of the Indian Ocean (between 9° and 12°S). In this layer, the formation of growing disturbances is possible due to the barotropic-baroclinic
instability of the system of zonal currents. 相似文献
17.
The eddy formation determined as an anticyclonic spin-off eddy of the Gulf Stream is analysed from the CTD data of surveys made in the Gulf Stream region. The differences in its structure and conditions of formation from cyclonic eddies of this type observed previously are examined. Barotropic instability of the Gulf Stream's main jet is considered as a possible reason for such unstable disturbances existing at the south boundary of the Gulf Stream.Translated by M. M. Trufanov. 相似文献
18.
19.
Kuniaki Okuda 《Journal of Oceanography》1973,29(5):221-226
Short-period temperature fluctuations were observed in the uppermost region of the seasonal thermocline in Lake Biwa-Ko, under the existence of the strong wind-stirring. In the observation period, the temperature profile had a sharp discontinuity at the bottom of the surface mixed layer, and a large gradient in the discontinuity layer of about 2-m thickness. The most dominant disturbances occurred in the discontinuity layer had the period of 2 to 3 minutes and the amplitude of about 1 m. They occurred intermittently with 5-to 15-minute intervals, and the growth and decay cycles were repeated locally. On the basis of these results, it is suggested that they were caused by the shear instability, and that such disturbances may control the erosion process of the seasonal thermocline. 相似文献
20.
边坡稳定是淤泥质海底航道安全运营的关键问题之一。海底航道边坡失稳滑塌过程的不同阶段浅地层剖面图像声纹特征不同。采用灰度共生矩阵和小波多尺度分解方法分析了航道边坡失稳滑塌过程浅地层剖面图像纹理特征。结果表明,对比度、能量、相关度和逆差距在边坡失稳滑塌过程中具有明显的差异,分别从不同方面刻画了浅地层剖面图像声纹的清晰度、纹理粗细、主要方向和规则性,以定量的形式显示其内在异质性。能量、相关度和逆差距的水平和垂直方向变化大于对角方向,水平方向波动最明显。浅地层剖面声强时间序列和垂向空间变化序列小波多尺度分解突出了声强变化的局部细节及其在各尺度上变化的强弱分布和突变点位置,克服了常规人工识读的困难,这些声纹特征是边坡失稳滑塌预测预警的重要依据,有助于对海底航道边坡稳定性的探测。 相似文献