大地形上空地转基流中波动的传播和稳定性

研究表明，地形北坡上空东风基本气流中的重力惯性波最易出现不稳定发展，地形坡度大于１‰的地形南坡上空强西风气流中重力惯性波和地形罗斯贝波都是不稳定的。只有在西风气流中重力惯性波才会出现明显的相对基本气流的东、西传播现象。     

经向基流和地形对惯性重力波的影响

采用分层浅水波方程组和ＷＫＢ方法，分别讨论了经向基流的垂直切变和南北走向的地形对二维惯性重力波的移速，稳定性以及发展的影响。     

垂直切变和地形影响下惯性重力波的发展

采用分层浅水波方程和ＷＫＢ方法，分别讨论了在基流垂直切变和地形的影响下，二维惯性重力波的稳定性及其发展，并根据理论结果试图解释１９９２年６月２１日发生在京津冀的一次飑线演变与惯性重力波之间的关系，这可能为飑线预报提供一种思路     

地形对重力惯性波发展的影响

本文研究了具有南北坡的地形对重力惯性波发展的影响。利用WKB方法，建立了含地形作用的重力惯性波能量方程。研究结果表明:在层结稳定的情况下，当扰动“上坡”（沿地形高度的升度方向传播）时，其能量将减少，即扰动将减弱；当扰动“下坡”（沿地形高度的负升度方向传播）时，其能量将增加，即扰动将发展。如层结为不稳定，情形则相反，即扰动“上坡”时将发展，“下坡”时将减弱。此外，文中对波动的稳定性问题也作了一些讨论。     

切变基流中惯性重力波的发展

采用分层浅水波方程、一简单的二层模式和ＷＫＢ方法，考虑基本气流的垂直切变，水平切变以及地形的影响，分析了惯性重力波的发展变化，得到有关导式波和曳式波发展的环境条件。     

大气层结的非均匀性对重力内波波射线的影响

文中利用ＷＫＢ近似，讨论了非均匀层结对惯性重力内波和纯重力内波能量传播路径的影响，得到了波的能量密度，广义波作用密度，和广义拟能密度守恒的条件，导得了重力内波不稳定的必要条件，给出了在波的传播过程中控制波射线折射的方程，得到了两类不同的临界层，最后还利用四阶Ｒｕｎｇｅ－Ｋｕｔｔａ方法计算了不同层结分布下的波射线。     

切变流中的CISK机制与惯性重力波

利用板对称，有切变的大气动力学方程组，由行波法导出非线性微分方程，通过非线性稳定性理论讨论方程的稳定性，求解了ＫＤＶ方程，并讨论了线性ＣＩＳＫ，非线性ＣＩＳＫ，惯性稳定度参数和大气风速垂切变对惯性重力孤波强度和宽度的影响，目的早通过了解影响惯性重力孤波发展的因子，更深入地理解低纬中尺度天气系统形成和发展的过程。     

水平切变基流中惯性重力波的发展

采用分层浅水波方程组和ＷＫＢ方法，建立了在基流的水平切变和地形的影响之下惯性重力波的能量方程，由此讨论波动的发展。主要得出：在急流的气旋性环流区，曳式波发展；在反气旋性环流区，导式波发展。在山脉的南北坡，导式波和曳式波均有发展的可能。     

台风中－α尺度重力惯性波的发展与暴雨增幅

通过数值模拟和诊断研究得出，９２１６号台风暴雨的增幅过程与台风中－α尺度重力惯性波的发展、传播，非均匀层结的分布以及积云对流潜热反馈有关。大尺度非线性平流项的作用激发出大尺度的重力惯性波，积云对流潜热加热作用导致非地转风场扰动大大加强，从而使重力惯性波波幅加大，上升运动增强，暴雨加大。当重力惯性波向稳定度减小的方向传播时，波能量最易加强     

低纬与中纬重力惯性波在非均匀场中发展和传播的比较分析

本文用WKBJ方法得到了低纬重力惯性波的方程组,讨论了它的发展和传播,并与中纬的重力惯性波作了比较,给出了低纬与中纬环境场对各自的重力惯性波影响的差异。     

EFFECTS OF TOPOGRAPHY ON PROPAGATION AND DEVELOPMENT OF INERTIA GRAVITY WAVE

Effects of topography on the propagation and development of inertia gravity waves areinvestigated by means of WKBJ method.The equation of wave action conservation is obtained.It isfound that the inertia gravity wave tends to propagate to the higher elevation area,meanwhile theamplitudes of the waves increase.While the inertia gravity waves propagate to a lower elevation area,their amplitudes decrease.     

ANALYTIC SOLUTIONS OF NONLINEAR WAVE EQUATIONS IN THE ATMOSPHERE

In this paper,starting with the nonlinear equations of atmospheric motion and using a relatively simple method,we have obtained the periodic solutions to the nonlinear inertia waves,internal gravity waves and Rossby waves.These solutions represent the characteristics of nonlinear waves in the atmosphere.A preliminary analysis reveals that as for the inertia waves and internal gravity waves with finite amplitudes, the larger the amplitudes are,the faster the waves propagate,but for the Rossby waves with finite amplitudes,the larger the amplitudes and wavelengths are,the slower the waves move.The practical senses of the solutions are also discussed in this paper. This paper gives a new way to study the nonlinear waves.This result has certain significance for the weather forecasting and the study of atmospheric turbulence.     

大气非线性波动方程的解

本文从非线性大气运动方程出发,用比较简洁的方法,求得了大气非线性惯性波、非线性重力内波和非线性Rossby波的周期解,这些解反映了非线性大气波动的特色。分析指出:对有限振幅的惯性波和重力内波,振幅大的波传播越快,而有限振福的非线性Rossby波,振幅大、波长长的波传播越慢;本文还分析了这些解的某些可能的实际意义。 这些非线性波的研究提供了解非线性方程的新的途径,而且,它可以与大家熟悉的线性波动进行比较。对于天气预报和大气湍流的研究都有一定的意义。     

Propagation of Envelope Solitons in Baroclinic Atmosphere

ＰｒｏｐａｇａｔｉｏｎｏｆＥｎｖｅｌｏｐｅＳｏｌｉｔｏｎｓｉｎＢａｒｏｃｌｉｎｉｃＡｔｍｏｓｐｈｅｒｅ￥ＴａｎＢｅｎｋｕｉ（谭本馗）（ＤｅｐａｒｔｍｅｎｔｏｆＧｅｏｐｈｙｓｉｃｓ，ＰｅｋｉｎｇＵｎｉｖｅｒｓｉｔｙ，Ｂｅｉｊｉｎｇ１００８７１）ＹｉｎＤ...     

静力稳定度对大地形降水影响的数值模拟研究

利用ARPS模式,通过调节过大地形山脉的湿大气静力稳定度进行敏感性试验,研究了湿大气静力稳定度对大地形降水的影响。结果表明,湿大气静力稳定度的改变影响了地形重力波的形成、维持和传播机制。当静力稳定度偏小时,地形重力波容易破碎,得不到有效维持;当静力稳定度偏大时,地形重力波又不易形成;仅当静力稳定度达到适合的强度时,地形重力波才能得到有效维持和传播。此外,垂直上升速度分布、辐合辐散运动及水汽的凝结输送等是影响大地形降水强度及分布状况的重要因素。     

The Impact of Mid- and High-Latitude Rossby Wave Activities on the Medium-Range Evolution of the EAP Pattern During the Pre-Rainy Period of South China

Based on the NCEP DOE AMIP II daily reanalysis data (1979–2005), the evolution of the East Asia/Pacific (EAP) teleconnection pattern during the pre-rainy period of South China is studied on the medium-range time scale. It is found that positive and negative EAP patterns share a similar generation process. In the middle and upper troposphere, Rossby wave packets emanating from the northeast Atlantic or Europe prop-agate toward East Asia along the Eurasian continent waveguide and finally give rise to the three anomaly centers of the EAP pattern over East Asia. Among the three anomaly centers, the western Pacific subtropical center appears the latest. Rossby wave packets propagate from the high latitude anomaly center toward the mid-latitude and the subtropical ones. The enhancement and maintenance of the subtropical anomaly center is closely associated with the subtropical jet waveguide and the incoming Rossby wave packets from the upstream. In the lower troposphere, Rossby wave packets emanate from the subtropical Asia toward East Asia. Positive and negative EAP patterns could not be regarded as "mirrors" to each other with simply reversed phase. For the positive pattern, the positive height anomaly center around the Scandinavia Peninsula keeps its strength and position during the mature period, and the Rossby wave packets thus propagate persistently toward East Asia, facilitating a longer mature time of the positive pattern. As for the formation of the negative EAP pattern, however, the incoming Rossby wave energy from the upstream contributes to both the enhancement and southeastward movement of the negative anomaly belt from the Yenisei River to the Bering Strait and the positive anomaly center around Mongolia. At the peak time, the two anomlous circulations are evolved into the Northeast Asia and the mid-latitude anomaly centers of the negative pat- tern, respectively. The energy dispersion of Rossby wave packets is relatively fast due to the predominant zonal circulation in the extratropics, causing a shorter mature period of the negative pattern. During the pre-rainy period of South China, the prevalence of the EAP pattern significantly affects the rainfall over the region south of the Yangtze River. The positive (negative) EAP pattern tends to cause positive (negative) precipitation anomalies in that region. This is different from the earlier research findings based on monthly mean data.     

一次东移西南涡过程的平流层重力波特征研究

基于WRF模式对2011年6月16—19日一次东移西南涡过程的模拟,开展了西南涡激发平流层重力波的特征研究。东移西南涡可以分为发展、强盛和减弱3个阶段,每个阶段均伴随着强降雨天气,但由于降水位置和强度的不同,平流层重力波的分布和强度也不同。西南涡发展阶段,平流层重力波主要位于低涡的东侧,并向东北传播;西南涡强盛阶段,伴随对流降水的强度和范围明显增大,平流层重力波的振幅和范围也显著增大,且围绕西南涡的东侧和南侧呈现出半环状的重力波分布特征可分为两支,东侧波动波列表现为东北西南向分布,南侧的波列表现为东—西向分布;西南涡减弱阶段,重力波的振幅和范围均减小。波谱分析表明,重力波的纬向波数频率谱关于零频率呈非对称分布,且随着西南涡的增强,波谱在小尺度范围显著增大,即强对流更容易激发出小尺度的高频波;经向波数频率谱在波数较小谱段关于零频率基本呈对称分布,但在波数较大谱段,也呈非对称分布,这说明受平流层东风气流的影响,重力波主要向东传播。     

Numerical prediction of an intense convective system associated with the July 1987 montreal flood. part I: Gravity waves and the squall line

Abstract

In this study, a 24‐h high‐resolution numerical prediction of a prefrontal squall line associated with the 14 July 1987 Montreal flood is employed to investigate the origin and role of mesoscale gravity waves in the development of the squall system. The 24‐h integration using an improved mesoscale version of the Canadian regional finite‐element model is first validated against available observations; then non‐observable features are diagnosed to reveal the relationship between deep convection and gravity wave events. It is shown that the model reproduces well many aspects of the squall line, such as the propagation and organization of the convective system, as well as its associated precipitation. It is found that gravity waves are first excited near Lake Erie, following the initiation of early convective activity. Then, these waves propagate eastward and northeastward at speeds of 20 and 35 m s^‐1, respectively. As the waves propagate downstream, deep convection radiates rapidly behind the wave trough axis, forming a long line of squall convection. Because the squall line moves with the gravity waves in a “phase‐locked” manner, deep convection has a significant influence on the structure and amplitude of the gravity waves. The sensitivity of the wave‐squall prediction to various parameters in convective parameterization is also examined.     

非均匀层结大气中的重力惯性波及其激发对流的物理机制

本文用WKBJ方法求解Boussinesq近似下的重力波方程,导出非均匀层结大气中重力惯性内波的一个守恒波作用量(称为广义波作用量)。根据广义波作用量守恒原理,着重讨论了重力惯性内波在发展过程中尺度变化的规律;在适当的条件下,重力波随着其尺度的变化而可能崩溃(或破碎),从而激发对流的发展。