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.     

地形和热源对冬季定常行星波形成的影响

本文用二层非线性原始方程谱模式，并在方程中考虑了Rayleigh摩擦、Newton冷却和温度水平扩散，在伟向均匀的初始场下，积分４０天，分别模拟了地形、热源单独作用和共同作用对冬季定常行星波形成的影响，尤其考虑了不同尺度地形和非定常热源的影响。     

北半球冬季行星波的传播及其输运作用

利用变换欧拉平均方程讨论了行星波动力学。观测和模拟结果都表明,在北半球冬季准定常行星波的经向传播存在两支波导。一支为高纬度波导,另一支则为低纬度波导。这些结果与理论分析相当一致。通过对EP通量进一步的研究表明,平流层爆发性增温是沿高纬度波导传播的异常行星波与平均气流相互作用的结果。而热带风场的准两年周期振荡（QBO）是低纬度平流层下层大气纬向平均流的一个重要年际变化,它可以影响行星波沿低纬度波导的传播;此外,由一个行星波一平均流耦合模式模拟的结果表明,这个热带风场的变化还可以通过波流相互作用调制行星波沿高纬度波导的传播。 行星波对臭氧的输运作用在文中也进行了分析。行星波强迫出的剩余平均环流表明,耗散的行星波有强的输运作用;向北的涡动热量输送可以强迫出一个正的输运环流,其在低纬度上升并在高纬度下沉。同时研究还表明,热带风场的QBO对行星波传播的调制对输运环流也有重要影响,模式结果表明,在QBO的东风位相期间行星波引起的输运作用明显增强,其结果可用于解释平流层高纬度臭氧的年际变化。     

冬季热源位置与热源的南北宽度对定常行星波的影响

本文应用一个定常、准地转34层球坐标模式来讨论冬季北半球多层模式大气对定常热源强迫的响应. 计算结果表明:在冬季位于高纬度的定常热源强迫所产生的定常行星波的振幅要比位于中纬度的定常热源强迫所产生的定常行星波的振幅要大.计算结果也表明了热源的南北宽度愈宽,其强迫所产生的定常行星波的振幅愈大.     

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。     

北半球冬季准定常行星波的三维传播及其年际变化

作者回顾了应用叶笃正先生所创立的Rossby波频散理论,来研究准定常行星波在三维大气的能量频散以及在北半球冬季三维大气中的传播规律,并应用NCEP/NCAR再分析资料和由大气环流数值模拟所得的模式资料的40年风场、温度场资料计算了冬季北半球准定常行星波的E-P通量.计算结果表明了北半球冬季准定常行星波在三维大气传播具有沿两支波导的传播特征,这与从理论分析所得的结果相吻合.作者还分析了冬季准定常行星波的E-P通量分布的年际变化,分析结果表明了准定常行星波在北半球冬季三维大气中传播的这两支波导有明显的年际振荡;并且,从冬季准定常行星波的E-P通量辐散辐合的年际变化与北极涛动的年际变化相比较,发现准定常行星波两支波导的年际振荡直接影响着北极涛动(AO),因而说明了准定常行星波活动的年际变化可以影响对流层的气候变化.     

球面大气中行星波的波作用守恒方程及用波作用通量所表征的定常行星波传播波导

大气运动的形式多种多样,大气中存在多种尺度的天气系统,大气中多尺度相互作用成为近几十年来关注的热点问题。该文对大气多尺度作用的研究进行了总结和回顾。目前,多尺度相互作用的研究主要集中在E-P通量、波包理论和大气能量学等方面,大致包含均匀基本气流和非均匀基本气流下的相互作用;正压大气和斜压大气条件下的相互作用;绝热和非绝热条件下的相互作用;正压大气和斜压大气有无地形效应条件下波包与基本气流的相互作用;波流相互作用中中尺度扰动波包的发展;多种尺度动能和有效位能之间的能量转换等。上述理论很好地解释了一些天气现象,比如平流层爆发性增温现象、北半球阻塞形式的形成和维持原因、寒潮爆发过程和西太平洋副热带高压变动以及与中国降水的相关性等。多尺度系统之间的相互作用在台风和梅雨锋暴雨过程中尤为重要,不同尺度系统相互影响以及不同尺度系统之间的能量转换对台风和梅雨锋暴雨的发生、发展以及消亡过程有重要的影响。

     

南北半球大气定常波的相互对应关系

本文利用NCEP／NCAR的月平均高度场资料，计算了全球各层月平均纬向偏差，分析结果表明，在对流层普遍存在着南北半球的奇对称现象，在4月和10月，这种对称性特别明显；在对流层低层，南半球的定常波动强度明显大于北半球，但在对流层中层，北半球的波动强度明显大于南半球，且南北半球都在冬季时达到最大振幅，在南半球全年和北半球的冬季，极区附近偶板子特征明显，在上半年，北半球偶板子按逆时针转动，而南半球则顺时针转动，在下半年，则情况相反。     

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.     

The role of precipitation in aerosol-induced changes in northern hemisphere wintertime stationary waves

The coupled climate model EC-Earth2 is used to investigate the impact of direct radiative effects of aerosols on stationary waves in the northern hemisphere wintertime circulation. The direct effect of aerosols is simulated by introducing prescribed mixing ratios of different aerosol compounds representing pre-industrial and present-day conditions, no indirect effects are included. In the EC-Earth2 results, the surface temperature response is uncorrelated with the highly asymmetric aerosol radiative forcing pattern. Instead, the anomalous extratropical temperature field bears a strong resemblance to the aerosol-induced changes in the stationary-wave pattern. It is demonstrated that the main features of the wave pattern of EC-Earth2 can be replicated by a linear, baroclinic model forced with latent heat changes corresponding to the anomalous convective precipitation generated by EC-Earth2. The tropical latent heat release is an effective means of generating stationary wave trains that propagate into the extratropics. Hence, the results of the present study indicate that aerosol-induced convective precipitation anomalies govern the extratropical wave-field changes, and that the far-field temperature response dominates over local effects of aerosol radiative forcing.     

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.     

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.     

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.     

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.     

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.