用Lagrange函数平均法研究非均匀基流中的地形Rossby波

本文提出可以用平均限制性变分原理来研究非均匀基流中地形对Rossby波的影响。所得到的结果与用多重尺度法相一致,但却避免了多重尺度法中的冗繁运算,而且物理意义更加清楚,诸如波作用量密度、波能密度等物理量的定义也更自然、合理。     

在非匀质波动中应用拉格朗日函数平均法应注意的问题

本文主要讨论了变分原理在解决有关非均质波动中存在的问题,并分析了使用普通变分原理、限制性变分原理、多重尺度法对惯性重力内波方程进行研究的结果,发现使用变分原理,限制性变分原理都是有条件的,即它们仅对某些类型的方程才有效,而对于有些方程用不同的方法,可得到不同的结果.这些对以后正确使用变分原理有一定的参考价值.     

基于变分原理的自适应网络技术及其权函数问题研究

利用两个具有解析解的算例研究基于变分原理的自适应网络技术。结果表明，对运动激波算例，权函数考虑二阶导数项比考虑梯度项更能有效地减小误差；对气旋锋生算例，仅以梯度作为权函数亦不能提高精度，考虑速度场、锋生函数分布的权函数能更合理地安排网络；对照解析解，发现提出的自适应网络技术能明显提高计算精度，在节省内存等方面显示了突出的优点。     

关于四维变分同化方法目标函数的权矩阵

本文运用概率统计理论讨论目标函数的权矩阵，证明了以误差协方差阵的逆为权矩阵的优越性，还证明了四维变分同化所得的初始场估计是渐近无偏的，同时又是渐近有效的。给出几种权矩阵模拟检验的结果，从而为选择合适权矩阵提供依据。     

非均匀介质中的Rossby波与Lagrange函数

本文从大气波动所满足的一般非线性方程入手,利用Lagrange函数平均法以及限制性变分原理求得了非均匀介质中Rossby波的频散关系式,波作用量方程,和平均能量方程取得了比较合理的结果。进一步验证了应用平均限制性变分原理求非线性大气波动Lagrange函函数的可行性,为今后用变分方法研究更复杂的非线性大气波动作出有益的尝试。     

多普勒雷达资料四维变分同化

文章从理论上分析了多普勒雷达资料的四维同化。阐述多普勒雷达资料四维同化的主要过程及其基本思路。着重论述多普勒雷达资料四维变分分析系统(4D-VDRAS)的原理和方法,以及价值函数,共轭方程、伴随方程和多普勒雷达数据处理、Barnes插值技术和4D-VDRAS的应用。     

物理协调大气变分客观分析模型及其在青藏高原的应用I: 方法与评估

本文系统地介绍了基于约束变分客观分析法构建的物理协调大气变分客观分析模型,并将模型首次应用于青藏高原那曲试验区。该模型可融合不同时空分辨率的多来源数据,通过利用地面降水和地面、大气顶部的热通量等大气上下边界的观测资料来约束调整探空观测变量,从而尽可能保证气柱内的质量、热量、水汽和动量收支平衡。对模型及其产生的第三次青藏高原大气科学试验那曲试验区2014年8月期间的大气分析数据集进行评估分析,结果表明模型生成的常规状态量很好地保留了观测特征,模型生成的重要大尺度衍生量（如,垂直速度、散度、温度/水汽平流、视热源、视水汽汇等）可以较好地反映试验期内大气柱的动力、热力和水汽结构特征,有利于对大气降水过程的分析研究。分析发现,350～400 hPa高度层是该时期那曲试验区的动力、热量和水汽的重要变化中心。从各种观测资料对模型生成的分析场的影响来看,探空观测对高空风场的影响最大,但这种影响的幅度在1 m/s以内;降水和上下边界通量观测主要影响大尺度衍生量,如垂直速度,其中降水主要影响降水时期的上升运动,通量观测主要影响弱/无降水时期的下沉运动。总体而言,物理协调大气变分客观分析模型具备较好的稳定性和合理性。     

最大熵原理对大气状态的约束

本文对分布函数概念,对已经找到的重要的气象中的分布函数,对如何从熵原理去理解它们作了综合介绍.文中还对如何将此用于数值天气预告、气候变迁研究作了分析.     

四维变分资料同化

用Lorenz模式作变分同化数值试验，通过对一个简单系统的讨论，对四维变分同化方法进行较深入分桥。利用Lorenz模式的数值试验，检验切线模式及伴随模式，并对目标函数及其梯度进行了检验。     

Gravity waves in the atmosphere

Summary Mathematical discussion is restricted to gravity waves of period short enough for the earth's rotation to be neglected, propagated horizontally through air whose horizontal velocity and static stability vary with height in the layers near the ground. The differential equation (15) is derived, describing how the vertical velocity of the wave motion varies with height for waves, of length 2 /k, at rest relative to the coordinate system. Boundary conditions are then applied—at the ground where the motion is horizontal, and above where the kinetic energy is finite—to give the relationship betweenk and the velocity of the wave relative to the air above (–W).This relationship is illustrated for all possible stable waves in fig. 2 for four different airstreams whose profiles of stability and velocity are set out in fig. 1. Remarkably different results are obtained; conclusions about the wave-properties of an airstream therefore depend very much on the model chosen.Two intervening chapters discuss the circumstances under which gravity waves are possible. Some of the conclusions are applicable to long waves also. Unstable waves are a very unusual occurrence, and very special circumstances are necessary to produce them, if they occur at all; they cannot lead to any phenomenon in which one wavelength predominates. Observable stable waves are not propagated over the ground but are at rest relative to their cause, except in the case of compression waves which are accompanied by no phenomena of the weather and travel with about the speed of sound. The most important stable waves are waves in the lee of mountains.

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Zusammenfassung Die mathematische Erörterung beschränkt sich auf Gravitationswellen, deren Periode kurz genug ist, um die Erdrotation unberücksichtigt zu lassen, und zwar speziell Wellen, die sich horizontal durch die Luft ausbreiten, deren horizontale Geschwindigkeit und statische Stabilität in den bodennahen Schichten von der Höhe abhängig sind. Es wird die Differentialgleichung (15) abgeleitet, die beschreibt, wie die Vertikalgeschwindigkeit der Wellenbewegung mit der Höhe bei Wellen variiert, die 2 /k lang und relativ zum Koordinationssystem unbewegt sind. Ferner werden Grenzbedingungen aufgestellt, wonach die Bewegung an der Erdoberfläche horizontal und darüber die kinetische Energie begrenzt ist, um die Beziehung zwischenk und der Wellengeschwindigkeit —W relativ zur oberhalb liegenden Luft anzugeben.Diese Beziehung wird in Abb. 2 für alle möglichen stabilen Wellen für vier verschiedene Luftströme veranschaulicht, deren Stabilitäts- und Geschwindigkeitsprofile in Abb. 1 dargestellt sind. Dabei ergeben sich auffallend verschiedenartige Resultate; Folgerungen über die Welleneigenschaften eines Luftstromes hängen somit stark von dem gewählten Modell ab.In zwei Zwischenkapiteln werden die Bedingungen besprochen, unter denen Gravitationswellen möglich sind. Mehrere Folgerungen daraus sind auch für lange Wellen gültig. Instabile Wellen kommen nur äußerst selten vor, da sie überhaupt nur durch ganz spezielle Bedingungen hervorgerufen werden; dabei können sie zu keiner Erscheinung führen, bei der eine einzelne Wellenlänge überwiegt. Stabile Wellen, die sich über der Erdoberfläche ausbreiten, können nicht beobachtet werden, da sie relativ zu ihrem Ursprung unbewegt sind, mit Ausnahme von Kompressionswellen, die sich ungefähr mit Schallgeschwindigkeit bewegen und keine Witterungserscheinungen verursachen. Die bedeutendsten stabilen Wellen sind auf der Leeseite von Gebirgen zu finden.

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Résumé La discussion mathématique se borne aux ondes de gravité de période assez courte pour qu'on puisse faire abstraction de la rotation de la terre et qui se propagent horizontalement dans l'air dont la vitesse horizontale et la stabilité statique varient avec l'altitude dans les couches voisines de la surface terrestre. On obtient l'équation différentielle (15) qui décrit la façon dont la vitesse verticale du mouvement des ondes varie suivant l'altitude dans le cas d'ondes d'une longueur de 2 /k en repos relativement au système des coordonnées. On tient compte des conditions aux limites — sur le sol d'une part où le mouvement est horizontal, et en haut d'autre part où l'énergie cinétique a une valeur finie — pour donner une relation entrek et la vitesse de l'onde (–W) relativement à l'atmosphère supérieure. Ces relations sont illustrées pour toutes les ondes stables possibles par la fig. 2 pour quatre courants d'air différents dont les profils de stabilité et de vitesse sont représentés dans la fig. 1. On obtient des résultats très variés. Aussi les conclusions que l'on peut tirer à propos des ondes formées dans un courant dépendentelles beaucoup du modèle choisi.Deux chapitres concernent les conditions dans lesquelles les ondes de gravité peuvent se produire. Quelques-unes des conclusions auxquelles on aboutit s'appliquent également aux ondes longues. Les ondes instables ne se produisent que très rarement et résultent de circonstances tout à fait spéciales; elles ne mènent à aucun phénomène où prédomine une seule longueur d'onde. Les ondes stables que l'on peut observer ne se propagent pas relativement à la terre; au contraire, sauf les ondes de compression qui ne sont accompagnées d'aucun phénomène visible du temps et se propagent à peu près à la vitesse du son, elles sont en repos relativement à leur cause. Les ondes stables les plus importantes sont celles qui naissent à l'abri des montagnes.

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With 2 Figures.     

Quasi-stationary planetary waves and temperature reference atmosphere

Summary A middle atmosphere temperature reference model from satellite measurements has recently been proposed. Comparisons are made with the Air Force Reference Atmosphere and the Reference model from satellite data. Large temperature deviations between two models at 60 N, 90 W in winter are found and the role of quasi-stationary planetary waves for these deviations is dicussed.With 3 Figures     

CISK-related Rossby Waves in the Tropical Atmosphere

In terms of a baroclinic quasi-geostrophic wave-filtering technique in connection with a dimensionless paramet-er, η(z), of condensation-released latent heat that indicates the CISK mechanism, a model is established for des-cribing tropical atmosphere CISK-Rossby waves alongside its analytical solution. Theoretical study shows that there exists pronounced difference between Rossby waves, CISK-involving and classic, and the former can be used to in-terpret some aspects of the low-frequency oscillation in the tropical atmosphere     

Oscillatory Rossby Solitary Waves in the Atmosphere

The linear Rossby wave frequency expression is expanded at higher accuracy based on the scale difference char?acteristics of atmospheric long waves in the and directions. That the nature of the waves represented by the expan?sion is identical to that of the original ones is demonstrated both in phase velocity and wave energy dispersion speed , followed by the derivation of the nonlinear expression describing atmospheric long wave behaviors with the associated approximate analytic solution obtained. Then, for the first time atmospheric’ oscillatory Rossby solitary wave’ with its dispersion relation is obtained by numerical calculation with the aid of physical parameters of the real atmosphere. The solitary wave is found to be very close to such longwave systems as blocking highs and cut-off de?pressions in the actual atmosphere.     

Nonlinear magneto-acoustic waves in the solar atmosphere

The weakly nonlinear evolution of quasi-isentropic magnetoacoustic waves in the solar atmosphere is analyzed. The plasma is assumed to be initially homogeneous, in thermal equilibrium and with a straight and homogeneous magnetic field frozen in. Additionally, the plasma is assumed to be cooled by the standard cooling function in the range of 10⁴ K<T<10⁷ K and heated by a mechanism which is proportional to the density and temperature. The range of temperature where the plasma is isentropically unstable, the e-folding time for thermal instability and the corresponding time and length-scale for wave breaking are found.     

Planetary stationary waves in the atmosphere Part I: Orographic stationary waves

It is proposed that the orographic stationary waves are required by long-term balance of momentum in the at-mosphere with zonally asymmetric orographic forcing, This hypothesis may be confirmed successfully with the theo-retical model of geostrophic waves. In the Part I, we will explain the observed phase distributions of orographic sta-tionary waves at middle and high latitudes of the Northern Hemisphere, according to the long-term balance of zonal momentum over the stationary orographic forcing. It is revealed that the geographic distribution of stationary waves depends not only on local topgraphy but also on mean circulation fields and angular momentum flux in the atmos-phere. So these waves cannot be simulated by the models in a restricted area.     

Activities of low-frequency waves in the tropical atmosphere and enso

ENSO, particularly the occurrence of ENSO is still an important research object in climatic variation. Using the ECMWF data, the relationship between ENSO and the activities of low-frequency waves in the tropical atmosphere is analyzed in this paper. It is shown that the occurrence of ENSO is closely related to the intraseasonal oscillation and the quasi-stationary waves (the period > 90 days) in the tropical atmosphere. Associated with the occurrence of El Nino event, the kinetic energy of low-frequency waves has obvious variation: the kinetic energy of atmospheric intraseasonal (30–60 days) oscillation (ISO) decreases abruptly and the kinetic energy of quasi-stationary waves increases abruptly. Moreover, the ISO and quasi-stationary waves propagate eastward clearly corresponding to El Nino; but they clearly propagate westward in La Nina cases.     

Planetary stationary waves in the atmosphere Part II: Thermal stationary waves

The contribution of thermal forcing to the planetary stationary waves will be studied also by assuming that heat balance in stationary waves over zonally asymmetric thermal forcing must be maintained over a long time period. Us-ing the same model of geostrophic waves introduced in Part I, we may explain successfully the observed and simulated responses to the thermal forcing in the atmosphere, such as the wave 1 structure at high levels of middle latitudes, the seasonal changes of the stationary waves in the Northern Hemisphere, the opposite phase distributions of stationary waves at high and low levels of the subtropical regions in both hemispheres and so on.     

正压大气中的螺旋行星波

本文对天气图上常见的螺旋状的行星波(Rossby波)的形式、发展以及其它方面的动力学性质作了理论分析,并讨论了它在维持大气环流中所起的作用。