冬季北半球地形与定常热源强迫所产生的定常行星波及其动量通量、热量通量的计算

本文应用一个包括Rayleigh摩擦、牛顿冷却、水平涡旋热量扩散、定常、准地转、34层球坐标模式来研究冬季北半球地形与定常热源强迫所产生的定常行星波。 本文计算了强迫所产生的定常行星波引起的动量通量与热量通量。计算结果与观测结果比较一致。 计算结果表明:最大向北的动量通量与热量通量位于平流层。     

夏季西藏高原对北半球定常行星波形成的热力作用

本文应用一个包括Rayleigh摩擦、Newton冷却与水平涡旋热力扩散的准地转34层球坐标模式来研究西藏高原对夏季北半球定常行星波形成的热力作用. 计算结果表明夏季位于西藏高原上空的热源对于北半球夏季定常行星波形成的热力作用要比高原地形的动力作用大得多. 本文还计算了夏季北半球地形与热源强迫所产生的定常行星波与等高面上定常扰动系统的分布,其计算结果与由实际观测所得到的分布比较一致.     

夏季西藏高原与落基山脉对北半球定常行星波形成的动力作用

本文应用一个包括Rayleigh摩擦、Newton冷却与水平涡旋热力扩散准地转34层球坐标模式来研究夏季西藏高原与落基山脉地形强迫对于夏季北半球定常行星波形成的作用. 计算结果表明:夏季北半球地形强迫所产生的定常行星波的振幅与位相分布与冬季的分布是很不一样的,夏季地形强迫所产生的定常行星波主要集中在亚热带的对流层,并且可以发现纬向波数k=1与k=2的振幅在高纬度存在着第二峰值.计算结果还表明了夏季西藏高原与落基山对于夏季定常行星波的形成起了重要作用.     

大气中定常行星波的Eliassen-Palm通量与波折射指数的关系

本文研究了β平面近似下波作用量守恒,得到波作用通量——Eliaaen-Palm通量的一般形式.本文还利用WKBJ方法求得球面大气中定常行星波的Eliassen-Palm通量与波折射指数的关系. 本文还用一个准地转34层球坐标模式计算了冬季北半球地形与定常热源强迫所产生的定常行星波的Eliassen-Palm通量,证明了冬季受迫定常行星波在垂直及侧向传播中存在着两支波导,从而证明了理论上所得到的关系.     

冬季低纬度热源异常在北半球对流层大气环流异常中的作用

本文首先从理论上讨论了北半球冬季低纬度强迫源与中纬度强迫源强迫所产生的准定常行星波在实际基本气流中传播路径及其振幅分布的差异,指出冬季低纬度热源异常将对北半球中、高纬度对流层大气环流的异常起很大影响,而中纬度热源异常将对平流层环流异常起很大作用。 本文应用一个包括Rayleigh摩擦、Newton冷却及水平涡旋热力扩散准地转34层球坐标模式分别计算了冬季低纬度热源异常与中纬度热源异常所造成北半球扰动系统的异常情况,计算结果表明了冬季低纬度热源异常将对中、高纬度对流层大气环流异常起很大作用,热带太平洋上空热源异常将产生PNA型环流异常。     

冬季格陵兰高原对北半球定常行星波形成的作用

本文应用包括Rayleigh摩擦、Newton冷却和水平涡旋热量扩散的定常、准地转、34层球坐标模式来研究北半球地形强迫所产生的定常行星波. 由模式所计算的结果表明:冬季在高纬度的地形——如格陵兰高原,在北半球地形强迫所产生的定常行星波中起着重要作用.     

热带基本气流对冬季北半球中高纬度准定常行星波的影响

本文利用一个包括Rayleigh摩擦、Newton冷却及水平涡旋热力扩散的准地转34层球坐标模式来研究冬季北半球地形与热源强迫所产生的准定常行星波与热带基本气流的关系。 计算结果表明,冬季热带平流层基本气流是西风时,其北半球中高纬度平流层波数2准定常行星波的振幅偏大;而当冬季热带平流层基本气流是东风时,其北半球中高纬度平流层波数2准定常行星波的振幅偏小,这与实际结果比较一致。 计算结果还表明冬季热带对流层基本气流对中高纬度准定常波的影响要比平流层基本气流的影响大。     

冬、夏平流层定常环流的数值模拟

本文应用一个包括Rayleigh摩擦、Newton冷却及水平涡旋热量扩散准地转34层球坐标模式来模拟北半球冬、夏两季平流层大气环流。利用Lindzen和Kuo所提出的方法来解这样一种复什二阶偏微分方程。 计算结果表明:由模式计算所得到的冬、夏两季北半球实际地形与实际热源强迫所产生的定常行星波振幅与位相的垂直分布及在平流层定常扰动系统的分布均与实际观测得到的分布相一致,这说明平流层的定常扰动分布主要还是由于对流层内地形与热源强迫所产生的定常扰动往平流层传播的结果。     

模式大气对于非绝热加热场的线性响应

本文利用一个包含了Newton冷却、Rayleigh摩擦以及▽~4型水平扩散等耗散作用的定常、斜压、线性初始方程三维谱模式,研究了热带和中纬度理想热源以及1979年1月北半球平均非绝热加热场对于冬季行星尺度的大气定常波的影响。数值试验结果表明,热力强迫作用的重要性可以与北半球大地形的动力强迫作用相比拟。利用1979年1月平均加热场作为强迫函数计算得到的强迫扰动,主要表现为纬向波数为2的行星波,并具有明显的斜压结构。热带地区纬向非均匀热源所激发的近似地沿大园路径传播的Rossby波列,对于热带区域与中、高纬大气之间的遥相关现象提供了一种可能的解释,同时,热带外区域的加热场对于整个半球范围内定常波的维持有着更显著的贡献。     

地形与热源强迫在亚洲夏季风形成与维持中的物理作用

本文利用变换的欧拉平均运动方程组及一个准地转34层球坐标模式来讨论地形与热源强迫对亚洲夏季风形成与维持的物理作用。 通过地形以及地形与热源强迫所产生的准定常行星波E—P通量的散度,强迫经圈环流及扰动地转风速的计算,表明了青藏高原东南部上空夏季的非绝热加热对于亚洲夏季风形成与维持起着重要作用,它远大于地形的动力作用。 计算结果还表明:地形与热源对亚洲夏季风形成与维持的物理作用中,它通过强迫经圈环流的作用要大于强迫波E—P通量的散度的作用。     

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.     

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.     

On the modelling of stationary planetary waves

The structure of the atmospheric stationary planetary waves is obtained by means of the quasi‐geostrophic linear model developed by Matsuno (1 970). To show the influence of the upper boundary condition on the structure of the waves, the latter is computed using a rigid top and a radiation condition. The modifications to the wave structure obtained when the upper boundary is lowered from a height of 65 km to 42.5 km, 32.5 km, and 22.5 km are examined. The effects of varying the vertical grid increment are studied through a comparison of the wave structures obtained with 6, 12, and 24 levels between 5 and 65 km.     

Upper boundary of the bora as a stationary frontal surface

Summary For the inclined stationary internal atmospheric boundary as is the upper boundary of the bora flow down the lee-side slope of an orographic obstacle, the dynamic forces must be appropriately balanced, similar as at the atmospheric frontal surfaces. Starting from this idea, a model for the bora flow conditions was developed. Introducing some special suppositions, the model finally consists of four partial differential equations, which are solved numerically.Numerical experiments with the model by changing parameters such as friction and warm air stratification, as well as initial values of the flow: thickness, velocity, inclination and air mass temperature difference, show interesting results and finings. The shape of upper bora boundary and the distribution of the bora velocity above and downward the slope are graphycally presented, as they develop under the influence of different values of the mentioned parameters.With 5 Figures     

2004年秋季贵州静止锋天气分析

利用实况资料,从天气学角度对2004年秋季贵州静止锋天气进行分析,指出2004年秋季贵州静止锋天气主要以降雨为主,静止锋与冷空气的影响有关,500hPa引导气流、700hPa、850hPa西南气流的强弱以及地面冷空气的影响程度,决定了静止锋的强弱及维持时间.     

The characteristics of the forced stationary planetary wave propagations in summer Northern Hemisphere

The three-dimensional propagations of the forced stationary planetary waves in a realistic summer current, in which the vertical and horizontal wind shears are included, are discussed by using the refractive index squared of waves in a spherical coordinate system.The results show that there is no polar wave guide in stationary planetary wave propagations in summer. Thus, stationary planetary waves cannot propagate into the stratosphere. However, there are a wave guide pointing from the subtropics toward middle and high latitudes in the troposphere and another wave guide pointing from the lower troposphere at middle latitudes toward the upper troposphere near 30°oN in the forced stationary planetary wave propagations.A linearized, steady-state, quasi-geostrophic 34-level spherical coordinate model with Rayleigh friction and Newtonian cooling, horizontal kinematic thermal diffusivity is used to simulate the wave guides of three-dimensional propagations of stationary planetary waves in summer.     

Spatial reorganization of SST anomalies by stationary atmospheric waves

The dynamics of sea surface temperature (SST) anomalies that force stationary atmospheric waves, which in turn, feed back on the SST field is addressed. The phenomena is isolated by analyzing the dynamics of a slab ocean that is thermally coupled to an atmospheric model. Particular emphasis is put on identifying SST structures that are weakly damped by the joint effect of air–sea heat transfer and atmospheric wave dynamics.A frame work is presented that singles out long-lived SST features in a slab ocean coupled to an arbitrary linear atmospheric model. It is demonstrated that an SST anomaly eventually disintegrates into a number of propagating wave packets. The wave packets are confined in a Gaussian envelope, and each packet is tied to a stationary wave of a particular wavelength. These structures are a manifestation of coupled SST-atmosphere mode, for which the atmosphere and the ocean nearly are in thermal equilibrium. However, a small disequilibrium causes the wave packet to propagate and to broaden in an apparent diffusive manner.Central ideas pertaining to the mid-latitude SST dynamics are illustrated by analyzing the thermal feedback between a two-level atmospheric model (on a β-plane) and a dynamically passive slab ocean. The relevance of the present idealized coupled-modes to the SST variability in the mid-latitudes and in atmospheric GCMs coupled to slab oceans is discussed.     

北半球500 hPa高度场定常波不平稳性分析

提出并阐明Lorenz环流分解意义下的定常波不平稳性概念,它是月平均网上纬向波动分量气候变率与定常波强度相对大小的表征.根据Lorenz环流分解,定义全域(局域)定常波不平稳度Ius(I1us),分析了北半球500 hPa位势高度场定常波强度较大的30°-60°N纬带的定常波不平稳性,结果表明:(1)全城定常波不平稳带位置存在季节件北进、南退过程.平稳的定常波出现在冬季的35°-55°N的中纬度带和夏季的副热带地区(35°N以南),分别与冬季的东亚大槽、北美槽和较弱的欧洲槽,以及夏季的副热带高压等系统相联系.不平稳度的高值中心出现在春季的35°N和夏季的50°N,这与定常波强度季节变化和月平均图上槽脊位置、强度年际异常有关.(2)局域定常波不平稳度存在着明显的纬向不对称性.平稳带通常位于定常波的强槽强脊所控制的区域,而不平稳带通常位于定常波强度较弱的区域.副热带(35°N及以南)局域定常波不平稳度冬强于夏,中纬度(35°N及以北)则夏强于冬.夏季局域定常波不平稳度地理分布具有复杂的结构.但无论冬夏,北欧是定常波最不平稳的地区,北美大陆附近的定常波则相对平稳.(3)夏季,从华北经东北至北太平洋存在一个定常波不平稳度高值带,其高值中心位于中国黑龙江省东部(45°N,130°E),主要影响中国北方(东北、华北、西北),可能是该区夏季气候脆弱带的环流成因.     

The structure and propagation of stationary planetary wave packet in the barotropic atmosphere

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 from the great circle with significant difference if the shear of the basic zonal flow is not too small; (b) being superimposed on a westerly jet flow with positive shear (Uλ/y>0), the stationary wave packets excited by low-latitudinal forcing are first intensified during their northeastward propagation in the Northern Hemisphere, then reach their maximum of amplitude at some critical latitude, and after that weaken again; (c) the connected line of extremes (the positive and negative centres) of wave packet does not coincide with but crosses the ray by an angle, the larger the scale of external forcing, the larger the angle; and (d) the whole pattern of a trapped stationary wave packet is complicated by the interference between the incident and reflected waves.     

On the solution of the stationary,baroclinic Ekman-layer equations with a finite boundary-layer height

The stationary, Ekman-layer equations have been solved in closed form for two expressions of the eddy viscosity as a function of height, z: v _τ=cu*z(1?z/h)and v _τ=cu*z(1?z/h) ², where u* is the friction velocity, h the boundary-layer height and c a constant. The main difference between both solutions is that the quadratic K-profile leads to a velocity discontinuity at the top of the boundary layer, while the solution for the cubic profile approaches the geostrophic wind at z=h smoothly. We discuss the characteristics of the solutions in terms of a dimensionless parameter C=fh/cu*, where f is the Coriolis parameter. The dependence on C can be interpreted in terms of a varying boundary-layer height or in terms of stability. The results for C ~ 1 are related to a neutral boundary layer. They agree well with results of a second-order model. The limit C → 0 is investigated in detail. We find that the stress profile becomes linear. The velocity profile shows different characteristics depending on whether we consider a shallow or a very unstable boundary layer. The results agree with observations. Finally we consider the influence of baroclinicity on the wind and stress profiles.