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运用台风移动涡旋影响域统计分析动态区域序列概念,采用 3个目标台风卫星TBB资料 ,对台风螺旋云带波列结构特征进行了功率谱合成分析。研究结果揭示出台风涡旋中心与周 边区域对流云的相关场呈螺旋带波状特征;台风影响域螺旋波亦表现出显著次天气、中尺度 波动特征,其波动周期尺度及其传播相速可类似重力内波与涡旋Rossby波,即周期呈双峰特 征,为大于6h与24h左右时间尺度;螺旋波高、低空流型特征与台风的维持、发展结构特征 相关;扰动TBB场时间偏差分布呈类似涡旋Rossby波螺旋波列,其波列路径与涡 旋Rossby波传播特征相似,并提出了台风涡旋螺旋波结构模型。 相似文献
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在多极源声测井中, 低频弯曲波或螺旋波被广泛应用于测量地层的横波速度. 前人的研究已证明在各向同性地层中井孔伪瑞利波、弯曲波及螺旋波的低频极限速度都等于地层横波速度. 大量的数值计算结果似乎表明此结论在横向各向同性(TI)地层情况下也能成立, 但缺乏理论证明. 本文在井孔平行于TI弹性地层对称轴的模型下, 考察了井内声源激发的波在流-固边界上的反射和透射情况, 阐述了非泄漏模式导波产生的必要条件并讨论了其速度上限值. 我们发现在各向异性参数满足一定条件的TI地层中,导波速度的低频极限值小于沿井孔方向上的横波速度. 通过对井孔导波的频散分析以及对时域全波列的数值模拟, 论证了在这类地层中进行多极源声测井时,不可能根据弯曲波或螺旋波的到达时间准确获取地层的横波速度值. 相似文献
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本文中采用二层线性模式讨论了地面摩擦,水平热量交换和动量交换,以及长波辐射冷却等因子对长波稳定状况的影响.并且给出了相应的温压场结构,由理论上证实了当温度波还落后于气压波时,运动就已经开始阻尼的这个事实. 相似文献
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本文中采用二层线性模式讨论了地面摩擦,水平热量交换和动量交换,以及长波辐射冷却等因子对长波稳定状况的影响.并且给出了相应的温压场结构,由理论上证实了当温度波还落后于气压波时,运动就已经开始阻尼的这个事实. 相似文献
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在热带太平洋,观测数据表明海表叶绿素(Chl)表现出年际尺度变率和由热带不稳定波(TIW)引发的中小尺度扰动这两者的共存现象;两者通过海洋生物引发的加热(OBH)反馈对ENSO造成的联合影响尚未得到充分的表征和理解.本文利用一个混合型大气-海洋物理-生物地球化学耦合模式(HCM AOPB)来量化年际和TIW尺度上Chl扰动对ENSO的单独以及联合调制影响. HCM敏感性试验结果证实了两者对ENSO振幅存在相反的作用,其中大尺度Chl年际变率造成的海洋生物-气候反馈效应通过其对上层海洋层结和垂向混合的影响来减弱ENSO,而TIW尺度的Chl扰动则倾向于增强ENSO.气候模式中ENSO的模拟敏感地依赖于对不同尺度上Chl效应的表征方式,因此有必要在气候模式模拟中充分地考虑不同尺度上Chl引发的气候效应.本文揭示了热带太平洋Chl效应是气候模式中ENSO模拟的一个偏差源,可为不同尺度上热带太平洋气候系统与海洋生态系统间相互作用提供新的见解.这些结果也揭示了ENSO调制的复杂性:即热带太平洋海洋生物地球化学过程相关的年际和TIW尺度上的Chl扰动与物理过程间的相互作用可对ENSO产生协同效应. 相似文献
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对于一个包含许多大震震源的复杂系统来说,当外界对它的供能稳定、且边界条件变化不大时,该系统处于定态。定态系统的演变过程呈线性规律,涨落水平稳定。虽然系统的宏观状态不随时间变化,但系统内部仍可发生宏观过程,并会出现局部的突变。在突变前局域往往出现非线性行为。因此定态系统的每一次涨落与其子系统的突变相对应。由定态系统的上下限可预测未来地震发生的时间和强度,由系统的非线性行为可确定其地点。本文以1976年松潘7.2级地震为例对所提思路和方法作了检验.应当指出,当复杂震源系统和其子系统均处于非稳定态时,则确定性预报不能进行。 相似文献
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文中对含两种不相混流体的饱和孔隙介质模型进行了波场模拟,该模型基于封闭型系统假设,考虑了流相与固相的相对运动和孔隙率、饱和度(毛细管压力)的松弛机制,可以较好的模拟波场的数值衰减。与目前常用的等效流体方法和基于开敞系统假设的非饱和孔隙介质模型相比,更符合勘探阶段的实际情况。前人对该介质模型平面波的速度和衰减做了一定的研究,但对整个波场的计算研究还未见报道。本文推导了该模型包含毛细管压力和孔隙度松弛机制的波动方程,并利用有限元的方法进行了波场模拟,并对波场特征进行了分析。数值模拟结果表明,在地震频段,非湿相位移波场中慢波p3较为清晰;毛细管压力(饱和度)和孔隙度的松弛效应对非湿相流体位移有较大影响,随松弛系数的增大,位移减小。 相似文献
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依据水平风矢量场的分解思路,应用调和-余弦的二维风场分解方法,对水平风场的加速度迁移项也进行调和-余弦的分解,引入加速度迁移项位势概念,用加速度迁移项对应的位势分量部分对东移高原低涡及登陆台风系统的演变过程进行分析.结果表明:加速度迁移项位势对东移高原低涡系统有较好的描述作用.利用加速度迁移项位势追踪东移的高原低涡系统比常用的500 hPa位势高度场对低涡进行追踪更为清晰.此外,加速度迁移项位势在登陆台风Bilis的分析中也有较好的应用,可用以指示台风系统,判断台风中心的位置以及表示台风强度的变化.由于加速度迁移项位势可反映出水平风场平流的辐合辐散特征,因此对低涡及台风等与平流场的辐合辐散关系密切的天气系统的动力结构有较好的识别能力,可以作为一个新的动力诊断变量来诊断示踪天气系统的演变. 相似文献
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Fifty-seven days of moored current records are examined, focusing on the sequential passage of Typhoons Nesat and Nalgae separated by 5 days in the northwestern South China Sea. Both typhoons generated strong near-inertial waves(NIW) as detected by a moored array, with the near-inertial velocity to the right of the typhoon path significantly larger than to the left. The estimated vertical phase and group velocities of the NIW induced by Typhoon Nesat are 0.2 cm s-1 and 0.85 m h-1, respectively,corresponding to a vertical wavelength of 350 m. Both the vertical phase and group velocities of the NIW induced by Typhoon Nalgae are lower than those of Typhoon Nesat, with the corresponding vertical wavelength only one-half that of Nesat. The threshold values of induced near-inertial kinetic energy(NIKE) of 5 J m-3 reach water depths of 300 and 200 m for Typhoons Nesat and Nalgae, respectively, illustrating that the NIKE induced by Typhoon Nesat dissipated less with depth. Obvious blueshifts in the induced NIW frequencies are also detected. The frequency of NIW induced by Typhoon Nesat significantly increases at water depths of 100–150 m because of Doppler shifting, but decreases significantly at water depths of 100–150 m for Nalgae because of the greater influence of the background vorticity during the passage of Typhoon Nalgae. 相似文献
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The present article displays the results of theoretical investigation of the planetary ultra-low-frequency (ULF) electromagnetic wave structure, generation and propagation dynamics in the dissipative ionosphere. These waves are stipulated by a spatial inhomogeneous geomagnetic field. The waves propagate in different ionospheric layers along the parallels to the east as well as to the west and their frequencies vary in the range of (10–10−6) s−1 with a wavelength of order 103 km. The fast disturbances are associated with oscillations of the ionospheric electrons frozen in the geomagnetic field. The large-scale waves are weakly damped. They generate the geomagnetic field adding up to several tens of nanotesla (nT) near the Earth's surface. It is prescribed that the planetary ULF electromagnetic waves preceding their nonlinear interaction with the local shear winds can self-localize in the form of nonlinear long-living solitary vortices, moving along the latitude circles westward as well as eastward with a velocity different from the phase velocity of the corresponding linear waves. The vortex structures transfer the trapped particles of medium, as well as energy and heat. That is why such nonlinear vortex structures can be the structural elements of the ionospheric strong macro-turbulences. 相似文献
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A theory of enhanced saturation of the gravity wave spectrum due to increases in atmospheric stability 总被引:1,自引:0,他引:1
In this paper we consider a vertical wavenumber spectrum of vertically propagating gravity waves impinging on a rapid increase in atmospheric stability. If the high-wavenumber range is saturated below the increase, as is usually observed, then the compression of vertical scales as the waves enter a region of higher stability results in that range becoming supersaturated, that is, the spectral amplitude becomes larger than the saturation limit. The supersaturated wave energy must then dissipate in a vertical distance of the order of a wavelength, resulting in an enhanced turbulent energy dissipation rate. If the wave spectrum is azimuthally anisotropic, the dissipation also results in an enhanced vertical divergence of the vertical flux of horizontal momentum and enhanced wave drag in the same region. Estimates of the enhanced dissipation rates and radar reflectivities appear to be consistent with the enhancements observed near the high-latitude summer mesopause. Estimates of the enhanced mean flow acceleration appear to be consistent with the wave drag that is needed near the tropopause and the high-latitude summer mesopause in large-scale models of the atmosphere. Thus, this process may play a significant role in determining the global effects of gravity waves on the large-scale circulation. 相似文献
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The influence of tropical Indian Ocean warming on the Southern Hemispheric stratospheric polar vortex 总被引:1,自引:0,他引:1
ShuangLin Li 《中国科学D辑(英文版)》2009,52(3):323-332
During the past decades, concurrent with global warming, most of global oceans, particularly the tropical Indian Ocean, have
become warmer. Meanwhile, the Southern Hemispheric stratospheric polar vortex (SPV) exhibits a deepening trend. Although previous
modeling studies reveal that radiative cooling effect of ozone depletion plays a dominant role in causing the deepening of
SPV, the simulated ozone-depletion-induced SPV deepening is stronger than the observed. This suggests that there must be other
factors canceling a fraction of the influence of the ozone depletion. Whether the tropical Indian Ocean warming (IOW) is such
a factor is unclear. This issue is addressed by conducting ensemble atmospheric general circulation model (AGCM) experiments.
And one idealized IOW with the amplitude as the observed is prescribed to force four AGCMs. The results show that the IOW
tends to warm the southern polar stratosphere, and thus weakens SPV in austral spring to summer. Hence, it offsets a fraction
of the effect of the ozone depletion. This implies that global warming will favor ozone recovery, since a warmer southern
polar stratosphere is un-beneficial for the formation of polar stratospheric clouds (PSCs), which is a key factor to ozone
depletion chemical reactions.
Supported by National Natural Science Foundation of China (Grant Nos. 40775053 and 90711004), National Basic Research Program
of China (Grant No. 2009CB421401), and Innovation Key Program of Chinese Academy of Sciences (Grant Nos. KZCXZ-YW-Q11-03,
KZCZ2-YW-Q03-08) 相似文献
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Abstract An analytical spectral model of the barotropic divergent equations on a sphere is developed using the potential-stream function formulation and the normal modes as basic functions. Explicit expressions of the coefficients of nonlinear interaction are obtained in the asymptotic case of a slowly rotating sphere, i.e. when the normal modes can be expressed as single spherical harmonics. 相似文献
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John P. Boyd 《地球物理与天体物理流体动力学》2019,113(5-6):623-666
ABSTRACTIn an age of billion dollar particle accelerators and Mars rovers, it is surprising that solitary waves were first discovered by a man on horseback with no tools but his own eyes. A century and a half later, more complicated patterns of ridges, so-called hyperelliptic two-polycnoidal waves, were discovered in the ocean during a beach vacation. The inverse scattering method, which solves nonlinear partial differential equations through a sequence of solving purely linear equations, is a blend of quantum theory and hydrodynamics that arose from informal, unstructured conversations (i.e. goofing off) among a group of postdocs from different disciplines who were randomly assigned to the same office. The cnoidal wave in the lemniscate case is well-approximated by a nonlinear solitary wave and equally well approximated by a linear sine wave. It is always and exactly the superposition of solitary waves even in the limit in which it is an infinitesimal sine wave. The history and science of solitary waves has the disorienting quality of an M. C. Escher drawing. Here, we cannot give an understanding of these deep subjects in so brief an article; rather we strive to unveil the beauty and unexpectedness of these topics to give the reader a reason to pursue these in the much more comprehensive reviews and books we cite. Further, we stress the “scotomas” (blind spots), misconceptions and surprises, the sociology and epistemology of science. It is true that failed theories, scotomas, serendipity and cognitive saltation (progress in jumps) is characteristic of science. It is also true that the invention of the train was the invention of the train wreck. Engineering learns from each disaster and science should do the same. The highly nonlinear history of nonlinear waves is reported not to disrespect the past but to replace scientific fatalism with a constructive wariness. We are not smarter or more enlightened than Scott Russell or Stokes or Landau, but we can learn from their scotomas and misconceptions as much as from their triumphs. 相似文献