Plumb三维波作用通量和EP剖面图——对定常波模式输出结果的诊断分析

本文利用Plumb(1985年)所导出的线性、准地转定常波的三维波作用通量和Eliassen-Palm(EP)剖面图,对于一个线性和一个非线性的关于大气定常波的斜压初始方程三维谱模式的若干输出结果进行了诊断分析。分析结果表明,Plumb通量和EP剖面图,不仅可以用来诊断波作用在三维空间的传播、波动与纬向平均气流之间的相互作用,而且也可以用来诊断非线性作用的显著性,在利用它们对于观测资料进行诊断分析时,应当充分注意到非线性作用的影响。     

纬向切变基流中的非线性正压Rossby波

在半地转近似下，用相角函数方法得到了包含纬向基流及其切变的非线性常微分方程。利用常微分方程解的拓扑性质的定性理论，直接得到该方程存在有限振幅的周期波解与孤立波解即非线性正压Ｒｏｓｓｂｙ波解存在的条件，由此分析了纬向切变基流对波解存在的影响。最后利用函数逼近法求得了非线性正压Ｒｏｓｓｂｙ波解的显式表达式。结果表明，纬向切变基流对波的影响不仅表现在波的存在方面，而且还表现在波的形态方面，反映了波的非线性特点和基流对波动的作用。     

初夏东亚—太平洋遥相关波列年际变化的一种物理机制

根据1978-2002年北半球500 hPa高度场、地表温度场以及中国夏季雨带类型资料,应用最小二乘法获得了能反映1978-2002年各年北半球大气环流演变大尺度特征的25组空间谱函数.采用改进的低截谱模式方法和多种统计假设检验方法获得了夏季东亚-太平洋遥相关波列年际变化的一个物理机制.结果表明,当大气环流的内部动力过程中大尺度波-波和波-流相互作用明显时,大气环流的演变表现出明显的非线性特征,导致初夏从低纬到高纬东亚-太平洋遥相关波列多为"-、+、-"分布,相应的-EAP指数多为正值,西太平洋副热带高压北跳明显,相应中国夏季多雨区主要位于淮河流域及其以北地区;反之,当大气环流的内部动力过程中大尺度波-波和波-流相互作用较弱时,大气环流的演变表现出较为明显的线性特征,初夏从低纬到高纬东亚-太平洋遥相关波列为"+、-、+"分布,EAP指数多为负值,夏季西太平洋副热带高压北进不明显,相应中国夏季多雨区主要位于淮河、长江流域及以南地区.     

热带大气能量频散波射线的低频动力学特征

首先在非零频波条件下采用有、无辐散两类数学模型 ,讨论热带大气低频波传播动力特征 ,研究结果表明 ,非零频的波频率参数是热带大气低频振荡源能量频散波路径及其波振幅的关键影响因子 ,且热带地区低频振荡的经向传播与其伴随着的强对流云团有显著相关 ,并与热带低纬 β因子等相关。文中还进一步揭示了低纬大气低频振荡经向传播伴随的积云对流现象及向高中纬传播机理 ,描述了 WKB近似方法数学模型及其波射线方程解模态对大气低频动力特性及其水汽分布垂直结构、不稳定层结等因子的响应特征。     

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。     

纬向切变基流中的非线性Rossby波

本文在半地转近似下讨论了纬向切变基流中的非线性正压Ｒｏｓｓｂｙ波，给出了存在波解的切变基流条件。     

平流层臭氧纬向分布季节变化和行星波的关系

通过分析1992—2001年的HALOE卫星资料,给出了各纬度带平流层的臭氧混合比的纬向分布结构,并分析了其季节变化的特征,同时,利用NCEP/NCAR再分析资料,分析了平流层行星波的结构及其与臭氧纬向分布的关系。结果表明:平流层臭氧混合比的纬向分布季节差异较大,在两半球的夏季平流层臭氧混合比的纬向分布较均匀,其它季节在中高纬的臭氧混合比高值区有一些扰动,并且随着纬度的增大其扰动加强,其中冬季它的扰动最强,这些都与平流层的行星波有相同的特点。对这两种资料进行波谱分析发现,在冬半球臭氧混合比在中高纬的纬向扰动有明显的1波信号,并且与位势高度的1波扰动有相同的位相,因此认为臭氧纬向扰动主要是由行星波引起的,并且在中高纬主要是1波的影响;而低纬地区由于不满足行星波上传的条件,所以臭氧纬向分布不受行星波的影响。分析行星波扰动对臭氧的输送作用也表明,行星波的扰动确实引起臭氧在经向上的输送,从而造成臭氧纬向分布的不对称,并且由于基本气流的输送作用,使得臭氧纬向扰动与行星波造成的原始扰动有一个位相差。     

基本气流的垂直切变作用下的低纬低频波

在低纬地区,风速的垂直切变也是很明显的,作者解释了这些纬向气流的垂直切变对低纬长波性质以及对不同模态的相互作用的影响,并且发现切变对低纬波动的影响具有明显的选择性.     

强迫耗散正压大气中四波共振

本文首次研究了含Ekman摩擦和非绝热加热的四波共振动力学．使用新的双时间尺度和新的时间变换式，由四波共振的广义Landau方程，导得普遍的非线性低频周期解，Ekman摩擦使得低频周期具有滞后和突变返回两个重要特征，而非绝热加热作用与中高纬准双周振荡有关，中高纬的30－50天振荡则与自由Rossby波准共振有关．本文还研究了四波共振产生的爆发性不稳定，指出较大振幅波产生的爆发性不稳定可能是阻塞迅速形成的又一重要原因，还首次得到在正压大气中Ekman摩擦能够激发爆发性不稳定．本文结果纠正了Craik于1985年提出的在流体力学中广泛应用的两个错误论断．     

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。     

热带大气和海洋运动的频率差异在海气系统演变中的作用

对热带太平洋地区850 hPa纬向风场、海表温度场月平均距平进行了谱分析。结果表明:纬向风距平与海表温度距平的振幅在El Ni?o或La Ni?a期间同时增长。而在其他期间,波振幅随时间呈相反变化趋势。在El Ni?o或La Ni?a事件发展期间,纬向风距平的位相角与海表温度距平位相角的差值在90o左右,而在事件的衰减期间,它们的位相角的差值在0o左右。本文还利用长波近似、海洋对大气加热取局地热力平衡近似时的简单热带海气耦合模式,研究了大气变量和海洋变量位相差随时间变化对海气耦合解的影响。在海气耦合模式中,当大气模式取为非定常时,大气和海洋Kelvin波之间以及Rossby波之间存在着能量转换,使大气和海洋波振幅呈相反变化趋势。此时,耦合波振幅随位相角差的变化没有共同的增长或衰减区间。大气Kelvin波与海洋Rossby波或大气Rossby波与海洋Kelvin波相互作用时,波振幅随位相差的变化存在着相同增长和衰减区间,它们的振幅要么同时增长,要么同时减少。当大气模式取定常时,因为相互作用波之间的位相差是一常数,波振幅随时间无限制增长。本文还在大气模式取为非定常和定常两种情况下,对海气耦合模式进行了数值求解。结果表明,当大气模式取为非定常时,数值解随时间的变化趋势跟观测结果有较好一致性。当大气模式取为定常时,数值解随时间的变化趋势跟观测结果差别较大。     

简单的热带海气耦合波——Rossby和Kelvin波的相互作用

本文分析了当大气和海洋中未经耦合前的自由波分别为Kelvin波和Rossby波,经相互作用后所产生的耦合波的性质。结果表明,不管大气的自由波为Kelvin波或Rossby波,而海洋的自由波为Rossby波或Kelvin波,经相互作用后的耦合波可以分成两类。一类耦合波的色散关系接近自由的Kelvin波;另一类则由不同经圈模的Rossby波经相互作用后的耦合波。这两类波都具有不稳定性。文中讨论了耦合波的传播和不稳定的物理机制,并指出这类不稳定的热带耦合波,对研究ENSO事件中的某些现象有一定的参考意义。     

THE INTERLINKAGE OF LARGE-SCALE SYSTEMS BETWEEN HIGH AND LOW LATITUDES RELATED TO PROPAGATION OF THE PLANETARY WAVE AROUND EAST ASIA IN SUMMER

This study has reviewed recent studies about impact of the Rossby wave propagation on theweather of East Asia.Then,we have focused on the northward progression of the subtropical highaffected by the propagations and their interaction.The following results are obtained:(1)The twokinds of meridional Rossby wave propagations often affect the East Asian weather in summer,which propagate in two conflicting directions(northwest-southeastward and southwest-northeast-ward).This is considered as the interaction of the large-scale systems between high and lowlatitudes with wave propagation,especially to the circulation systems around East Asia.(2)Thenorthward progression of the subtropical high is largely restrained,aecompanied by the southwardshift of the convective activity in middle latitudes,under the strong and persistent Rossby wavepropagation from high to low latitudes.And the opposite role could be found in the Rossby wavepropagation from low to high latitudes.     

THE INTERLINKAGE OF LARGE-SCALE SYSTEMS BETWEEN HIGH AND LOW LATITUDES RELATED TO PROPAGATION OF THE PLANETARY WAVE AROUND EAST ASIA IN SUMMER*

This study has reviewed recent studies about impact of the Rossby wave propagation on the weather of East Asia.Then,we have focused on the northward progression of the subtropical high affected by the propagations and their interaction.The following results are obtained:(1) The two kinds of meridional Rossby wave propagations often affect the East Asian weather in summer,which propagate in two conflicting directions(northwest-southeastward and southwest-northeast-ward).This is considered as the interaction of the large-scale systems between high and low latitudes with wave propagation,especially to the circulation systems around East Asia.(2) The northward progression of the subtropical high is largely restrained,aecompanied by the southward shift of the convective activity in middle latitudes,under the strong and persistent Rossby wave propagation from high to low latitudes.And the opposite role could be found in the Rossby wave propagation from low to high latitudes.     

THE DIABATIC WAVES IN BAROTROPIC MODEL

The equations of barotropic model are used to discuss the effects of diabatic factors such as heat-ing of convective condensation, evaporation-wind feedback and CISK on the Rossby wave and the Kelvin wave. In low latitudes we have obtained the angular frequency and analyzed the period and stability of waves. The result shows the existence of the diabatic factors not only enlarges the period of adiabatic waves but also changes the stability of waves. Thus we think that the so-called intraseasonal oscillation and some other low-frequency oscillations are a kind of diabatic waves which are important factors producing the long-term weather changes and short-term climatic evolution.     

论陆架波系动力学及其在厄尔尼诺信号传播中的作用

文中讨论了陆架波系和赤道波系在动力学上的相似性，和赤道波系一样，陆架波系也由惯性重力波、Ｋｅｌｖｉｎ波、Ｒｏｓｓｂｙ（长、短）波和有条件的Ｒｏｓｓｂｙ－重力混合波组成。指出，当　海洋三边存在陆架而一边为赤道时（如北太平洋），则陆架波系和赤道波系中的Ｋｅｌｖｉｎ波，　将以逆时针方向携带信号绕海盆一周，而两个波系中的Ｒｏｓｓｂｙ长波，将以顺时针方向绕海盆一周，即通过陆架波和赤道波为海洋中某些信号的传播组织成一个绕海盆的环路。这种物理　过程可望用以解释发生在海洋中的某些长周期现象，如Ｅｌ　Ｎｉ　ｏ现象。文中进一步　讨论了陆架波的各种简化运动。     

简单热带海气耦合模型中不同扰动形式间的耦合作用

在局地热平衡情况下研究了简单热带海气耦合模式中不同扰动形式间的耦合，依次讨论了由大气准定常Kelvin波与海洋R0ssby波、大气准定常Rossby波与海洋Kelvin波、大气准定常Kelvin波与海洋KelVin波、大气准定常Rossby波与海洋Rossby波组成的耦合系统的性质，并研究了存在于其中的耦合扰动的特征。     

Coupling mechanisms between equatorial waves and cumulus convection in an AGCM

In this study, we focused on the difference in appearances of the convectively coupled equatorial waves (CCEWs) in a simulation with the CCSR/NIES/FRCGC AGCM, between two experiments, one with and the other without implementation of the convective suppression scheme (CSS) in the prognostic Arakawa–Schubert cumulus parameterization. Realistic CCEW modes, i.e., Kelvin, Rossby, mixed Rossby-gravity (MRG), and n = 0 eastward inertio-gravity (EIG) wave modes, were reproduced in the with-CSS experiment, while only Rossby-wave-like signals appeared in the without-CSS experiment.By comparing the structures of the Kelvin wave mode and the Rossby wave mode in two runs, it was suggested that the structural difference between these two modes in conjunction with the difference in the controlling factor of cumulus convection determines the CCEW features. The CSS implemented here is such that cumulus convection is suppressed until the cloud-layer-averaged relative humidity exceeds the threshold of 80%. In the without-CSS model, only Rossby wave modes are coupled with the convection. This is because CAPE controls cumulus convection in this model, and the larger frictional convergence of Rossby wave mode prepares CAPE to generate favorable condition for cumulus convection. In the case of the with-CSS model, on the other hand, cumulus convection is largely controlled by the humidity in the free atmosphere. The convergence associated with the equatorial waves can produce the moisture anomaly to overcome the relative humidity threshold, and maintains the favorable condition for cumulus convection once it starts. In this case, not only Rossby waves but also Kelvin, MRG, and n = 0 EIG waves are reproduced more realistically. It is suggested that inclusion of some kind of mechanism connecting the free tropospheric moisture with the convection under the condition of abundant convective available potential energy could be a key factor for realistic coupling between large-scale atmospheric waves and convection.     

Advances in research on atmospheric energy propagation and the interactions between different latitudes

Early theoretical analyses indicated that the tropics and extratropics are relatively independent due to the existence of critical latitudes. However, considerable observational evidence has shown that a clear dynamical link exists between the tropics and midlatitudes. To better understand such atmospheric teleconnection, several theories of wave energy propagation are reviewed in this paper: (1) great circle theory, which reveals the characteristics of Rossby waves propagating in the spherical atmosphere; (2) westerly duct theory, which suggests a “corridor” through which the midlatitude disturbances in one hemisphere can propagate into the other hemisphere; (3) energy accumulation-wave emanation theory, which proposes processes through which tropical disturbances can affect the atmospheric motion in higher latitudes; (4) equatorial wave expansion theory, which further explains the physical mechanisms involved in the interaction between the tropics and extratropics; and (5) meridional basic flow theory, which argues that stationary waves can propagate across the tropical easterlies under certain conditions. In addition, the progress made in diagnosing wave-flow interaction, particularly for Rossby waves, inertial-gravity waves, and Kelvin waves, is also reviewed. The meridional propagation of atmospheric energy exhibits significant annual and interannual variations, closely related to ENSO and variation in the westerly jets and tropical upper-tropospheric troughs, amongst others.     

Seasonal Variation of Stationary and Low-Frequency Rossby Wave Rays

The wave rays and their seasonal variation of stationary and low－frequency Rossby waves are studied by using the Runge-Kutta scheme. The results show that for stationary waves the rays can reach lower latitudes in winter, and are limited in higher latitudes in summer. The main differences between the stationary and low-frequency wave rays are that low-frequency waves can propagate across the equator and the easterlies will not be an obstacle on their propagation. It explained to some extent the interaction of disturbances between the Northern and Southern Hemi-spheres. The lower wave frequencies and the stronger easterly flow are, the more difficult low-frequency waves will be to propagate across the equator. The waves with 20-day period are easier to propagate across the equator than that with 50-day period. The winter is the most favorable season for low-frequency waves to propagate into another hem-isphere.