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Monthly or seasonally mean anomalies of large-scale atmospheric circulation are better represented by wave packets or their combination. Both qualitative and quantitative analyses of equations of wave packet dynamics, which are obtained by the use of WKB approximation, are very helpful for the understanding of structure, formation and propagation of stationary and quasi-stationary planetary wave packet patterns in the atmosphere. Indeed, these equations of wave packet dynamics can be directly solved by the method of characteristic lines, and the results can be simply and clearly interpreted by physical laws. In this paper, a quasi-geostrophic barotropic model is taken for simplicity, and the wave packets superimposed on several ideal profiles of the basic current and excited by some ideal forcings are investigated in order to make comparison of the accuracy of calculation with the analytical solution. It is revealed that (a) the rays of stationary planetary wave packet do not coincide with but go away f 相似文献
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Blocking is one of the intensive atmospheric disturbances which can maintain for a long time. In this paprer we investigate the general conditions favorable for the generation and maintenance of the intensive disturbances. First, the evolutional process of disturbances superimposed on a jet-like zonal flow is studied by using the wave-packet representation and the WKBJ method. Second, the mechanism for generation and maintenance of disturbances is investigated by using the nonlinear equations and the general physical laws. Finally, some numerical experiments are given for illustration, showing the rapid absorption of disturbances by the jet-like zonal flow in one case and the maintenance of disturbances for a long time in the other case. 相似文献
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正压大气中扰动的演变 总被引：7，自引：2，他引：7
本文应用WKBJ方法研究正压准地转模式中小扰动的演变过程,提出扰动发展的判据应是扰动总能量和平均振幅同时增长。理论推导给出:正压扰动发展时波长变长,衰减时波长变短。文中详细地讨论了基本气流为平直西风的情况,得出急流南导波、急流北曳波为发展型,发展过程中槽线渐趋南北指向;急流北导波、急流南曳波为衰减型,槽线日渐趋于东西向。文中还讨论了基本气流为非平直气流情况,指出所谓“超长波后退”过程在一些情况下是发展型槽东移和波长变长所致。 相似文献
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本文研究正压大气中非均匀气流(特别是非平直基流)上扰动的演变过程,对[1]进行了推广,对迭加于超长波基流之上的长波扰动和迭加于超长波或长波基流之上的中、短波的扰动的演变特性进行了统一的处理。结果表明:当小槽、小脊的波长变长时,其振幅(能量)增大,扰动发展;波长变短时,振幅变小,扰动衰减。当小扰动已经发展成长波的时候,或者当我们一般地研究长波的演变过程的时候,则上述规律更为明显,即长波发展时,波长变长更为明显;长波衰减时,波长变短也更为明显。利用这些结果,可以解释大气中槽、脊发展时总是伴随着扰动加宽,而槽、脊收缩时,波长很快减小。其次,扰动发展与否完全由扰动的结构所决定,其中主要是由扰动轴线的方向及其与基流的相对位置所决定。北半球发展型扰动的轴线是:在急流以北呈东北—西南向,急流南呈西北—东南向;而衰减型的轴线是:急流北呈西北—东南向,急流南呈东北—西南向。这些结论和角动量传送理论结果以及天气实际都是符合的。 相似文献
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In part I of this paper, we have discussed two problems: the general properties of two-dimensional baro-tropie motion and the evolution and structure of both Rossby wave packet and inertio-gravity wave packet, In this part, we shall continue our discussion. Third, normal modes and continuous spectra of both quasi-geostrophic and non-geostrophic models, their different behaviour, and the comparison of normal mode approach to the wave packet approach. Fourth, weakly nonlinear theory of interaction based on the analysis of eddy transports, A nonzonal basic flow as well as non-geostrophic model is also included in the consideration, The last, the fully nonlinear theory, making emphasis on the conditions for the maintenance of nonzonal disturbances and the conditions for their continuous and complete absorption by the zonal flow. A comparison of Rossby wave absorption to energy cascade in the two-dimensional turbulence is also given. 相似文献
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波包及其与基流相互作用的分析和计算 总被引：2，自引：0，他引：2
本文将扰动按线性化位涡方程的谱函数展开,并和用WKB方法所得的结果相比较,指出:局地扰动或波包主要由连续谱组成,因而在过了一个相对短暂时段之后,波包中的槽脊线要变成倾斜的,波包要衰减,而且尺度要变短,由按谱展开法与由WKB方法所得结果是相互吻合的;但当在经过很长时段之后,由于和离散谱部分相对应的扰动占主要地位,WKB方法所得结论可能不再成立.其次,在弱非线性理论可应用的范围内,扰动所引起的动量传输、平均经圈环流以及基流的改变都可以较方便地用按谱函数展开的方法求得.文中还计算了一个波包演变及其对基流影响的例子,计算结果十分鲜明地显示出理论分析的结论。 相似文献
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一、天气系统的表示法·波包 试看北半球500毫巴高度场,如图10.1。其上有环绕北极的西风气流(基本气流),还叠加有槽、脊、高压中心和低压中心等高空天气系统。图10.1a中位于北欧的小槽发展并东移,两天后移至乌拉尔山附近(图10.1b);并引起下游弱脊增强,脊东侧形成强的偏北气流,第5天在东亚地区形成一次寒潮(图10.1c)。就图而论,上述演变过程是一目了然的。为了用动力气象学剖示流场和 相似文献
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