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。     

NUMERICAL STUDY OF TROPICS-EXTRATROPICS INTERACTION

A nonlinear steady-state baroclinic primitive-equation numerical model of atmospheric forced stationarywaves is used to investigate the tropics-extratropics interactions.Newtonian cooling,Rayleigh friction andbiharmonic horizontal diffusion are included in the model.The Eliassen-Palm (EP) cross-section and three-dimensional wave activity flux,which was derived by Plumb (1985) for linear quasi-geostrophic stationarywaves on a zonal flow,are used as diagnostics for the vertical and horizontal propagation of the waves.Results of the numerical experiments and diagnostics analyses suggest that the extratropical influenceon the tropical large-scale motion is important.The mid-latitude orographic forcing,especially of the Qing-hai-Xizang Plateau,and the extratropical thermal forcing make substantial contribution to the main-tenance of the cyclonic circulation over the eastern tropical and subtropical Pacific as well as the inversecirculation over the western Pacific in the upper troposphere.In addition,the longitudinal variation ofdiabatic heating in tropics has a significant influence on the wintertime stationary waves at higher latitudes.     

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。     

THE FORCING OF ANOMALOUS DIVERGENT WIND AND TRANSIENT VORTICITY FLUXES TO THE ANOMALY OF STATIONARY WAVES

The forcing of anomalous divergent wind and transient vorticity fluxes to the anomaly ofstationary waves of DJF (December—January—February) 1982/1983 is studied.The results showthat the anomaly of the transient vorticity flux convergence tends to cancel or dissipate the anomalyof the vorticity sources generated by divergent wind.The stationary wave anomalies are maintainedby both of these forcings.It is also found that,for the DJF 1982/1983 case,both of the vorticitysource anomaly over the tropical and equatorial eastern Pacific and that over the midlatitude NorthPacific are important to maintain the atmospheric circulation anomaly over the Pacific/NorthAmerica region.     

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.     

南边界强迫的非线性临界层与副高的形成、维持和振荡

用非线性准地转正压涡度方程模式，在南边界取定常强迫波，采用４种方案模拟了非线性临界层及其上激发的Ｋｅｌｖｉｎ猫眼，以确定热带的定常强迫对副高的形成、维持和振荡的影响。结果表明，南边界定常强迫仍在非线性临界层内激发行星尺度的准定常反气旋的Ｋｅｌｖｉｎ猫眼流场，猫眼的移动、强度和形状变化与夏季副高比较相似．而北边界定常强迫所得结果与夏季副高差异较大。因此，南边界所激发的非线性临界层上的Ｋｅｌｖｉｎ猫眼可能是夏季副高形成、维持和振荡的一种更为重要的新物理机制。文中还提出准定常行星波穿越副热带的非线性临界层的物理机制。     

北半球冬季平流层强、弱极涡事件演变过程的对比分析

利用1958～2017年逐日的NCEP/NCAR再分析资料对北半球冬季平流层强、弱极涡事件的演变过程进行了对比分析,同时比较了有平流层爆发性增温（SSW）和无SSW发生的两类弱极涡事件的环流演变和动力学特征。结果表明,强极涡的形成存在着缓慢发展和快速增强的过程,而弱极涡事件的建立非常迅速;和强极涡事件相比,弱极涡事件的峰值强度更强,异常中心的位置更高。此外,强、弱极涡事件的产生与波流相互作用的正反馈过程密切相关。对于强极涡事件,发展阶段的太平洋—北美（PNA）型异常削弱了行星波一波;当平流层西风达到一定强度,上传的行星波受到强烈抑制,使得极涡迅速增强达到峰值。而对于弱极涡事件,发展阶段一波型的异常增强了行星波上传,通过对纬向流的拖曳作用使得平流层很快处于弱西风状态,更多行星波进入平流层导致极涡急剧减弱甚至崩溃。针对有、无SSW发生的两类弱极涡事件的对比分析表明,有SSW发生的弱极涡事件发展阶段,平流层出现强的向上的一波Eliassen-Palm（EP）通量异常,通过正反馈过程使得一波和二波上传同时增强而导致极涡崩溃;无SSW发生的弱极涡事件发展阶段,平流层缺乏向上的一波通量,二波活动起到重要作用,其总的行星波上传远弱于有SSW发生的弱极涡事件。对于无SSW发生的弱极涡事件,其发展和成熟阶段对流层上部出现类似欧亚（EU）型的高度异常,伴随着强的向极的EP通量异常,导致对流层有极强的负北极涛动（AO）型异常。而有SSW发生的弱极涡事件发展阶段对流层上部主要表现为北太平洋上空来自低纬的波列异常,其后期的对流层效应更加滞后也不连续,对流层AO异常的强度明显弱于无SSW发生的弱极涡事件。     

大气动力学中三种Rossby波作用通量的特征差异和适用性比较

大气动力学诊断Rossby波的传播时,通常用波作用通量来表示。常用的三种波作用通量分别为Plumb波作用通量,T-N波作用通量和局地E-P通量。本文详细讨论了这三种方法的特征差异,并结合2016年1月的一次寒潮事件,比较了三种方法在该事件中的适用性。结果表明:1)Plumb波作用通量的纬向分量较大而经向分量较小,适用于振幅较小的纬向均匀的西风带Rossby长波的诊断。2)T-N波作用通量是对Plumb波作用通量的改进,经向分量得以增强,能更好地描述纬向非均匀气流中的较大振幅的西风带Rossby长波扰动。T-N波作用通量计算时,背景场取多年平均的当月气候场较合适,能更好地反映当前季节内的Rossby波传播异常。3)局地E-P通量可以诊断一段时间内天气尺度瞬变波对背景场(定常波)总的调控作用,但无法直接反映Rossby长波的逐时演变(T-N波或Plumb波作用通量则可以)。     

Southern hemisphere energy fluxes from analyses with special respect to the Weddell Sea region (antarctica)

Summary Meridional eddy transports of sensible heat and zonal momentum caused by transient and stationary waves are computed from Australian operational analyses. The southward sensible heat flux by transient waves is largest in the midlatitudes, where cyclones are responsible for the heat exchange. The flux decreases towards the Weddell Sea. The transport by stationary waves reaches remarkable values locally in the tropics and off the Antarctic coasts. The transport of zonal momentum is mostly accomplished by transient eddies. Zonal averages, horizontal distributions and fluxes along single latitudes are shown.With 12 Figures     

Feedback Mechanisms For The Atmosphere And Ocean Surface

Two kinds of feedback mechanisms in the coupling process between the atmosphere and ocean surface are identified in this paper. One is a negative feedback mechanism, which is effective in the dynamic interaction processes through momentum flux exchange. In this mechanism,the ocean extracts momentum from the atmosphere as a forcing field to generate waves, which decelerates atmospheric motions, lessening the intensity of synoptic systems. The second is a positive feedback mechanism, which is effective in the thermal interaction processes through heat flux exchange. This is a mechanism that is effective in the transport of sensible and latent heat fluxes to the atmosphere from the underlyingocean surface. As a result, the atmosphere obtains energy from the ocean, which intensifies atmospheric motions. For storm conditions typical of North Atlantic mid-latitudes, we consider these thermal and dynamical nteractions, the dominance of one over the other, and related implications for storm intensification.     

The Role of Topography and Diabatic Heating in the Formation of Dipole Blocking in the Atmosphere

In this paper, the nonlinear stationary waves forced by topography and diabatic heating are investigated. It is pointed out that (1) the nonlinear interaction of different stationary waves forced only by topography might form dipole blocking in the atmosphere, this might explain the dipole blocking appeared in the Pacific and Atlantic regions; (2) the dipole blocking could not be caused by the nonlinear interaction of the different stationary waves forced by the diabatic heating alone; (3) the nonlinear interaction of the diffferent stationary waves forced by both topography and diabatic heating could initiate dipole blocking in the atmosphere. In winter, the dipole blocking mainly occurs in the west regions of the Pacific and the Atlantic, and the heat source over the western part of the two oceans is advantageous to the formation of dipole blocking in the west of two oceans. However, in summer, the dipole blocking could be formed in the east part of the two oceans, and the heat source over the eastern     

The role of topography and diabatic heating in the formation of dipole blocking in the atmosphere

In this paper, the nonlinear stationary waves forced by topography and diabatic heating are investigated. It is pointed out that (1) the nonlinear interaction of different stationary waves forced only by topography might form dipole blocking in the atmosphere, this might explain the dipole blocking appeared in the Pacific and Atlantic regions; (2) the dipole blocking could not be caused by the nonlinear interaction of the different stationary waves forced by the diabatic heating alone; (3) the nonlinear interaction of the diffferent stationary waves forced by both topography and diabatic heating could initiate dipole blocking in the atmosphere. In winter, the dipole blocking mainly occurs in the west regions of the Pacific and the Atlantic, and the heat source over the western part of the two oceans is advantageous to the formation of dipole blocking in the west of two oceans. However, in summer, the dipole blocking could be formed in the east part of the two oceans, and the heat source over the eastern part of two continents is favourable for the formation of dipole blocking in the east regions of two oceans.     

Momentum flux of stratospheric gravity waves generated by Typhoon Ewiniar(2006)

The momentum flux of stratospheric gravity waves generated by Typhoon Ewiniar (2006) is examined using a Weather Research and Forecasting (WRF) model. In the stratosphere, zonal momentum flux with a positive sign by eastward-propagating waves is significant during the northward moving of the typhoon, while both zonal and meridional momentum fluxes with positive signs are significant during the typhoon decaying stage in which the typhoon moves northeastward. The magnitude of the momentum flux is greater during the mature stage of the typhoon than the decaying stage, and the phase speeds of the dominant momentum flux are less than 30 m s^?1 with a peak at 10–16 m s^?1. Positive momentum flux decreases with height overall in the stratosphere for both zonal and meridional components. The resultant gravity-wave drag forcing plays a role to decelerate the easterly background wind in the stratosphere. This drag forcing is relatively large above z = 40 km and below z = 20 km, and lower stratospheric wave drag is expected to affect the typhoon dynamics by modifying the background wind shear and inducing the secondary circulation in the troposphere.     

Spectral Behaviour of a Coupled Land-Surface and Boundary-Layer System

The temporal spectral response of a coupled land-atmosphere system to daily forcing of net radiation at the land surface is investigated using the analytic approach. The original definition of the problem dates back to an early study by Lettau. The present study builds on the problem and introduces some important additions, with a focus on the propagation of heat flux and temperature waves in both the soil and the atmospheric boundary layer. The study highlights the dependence of the complex amplitude of surface temperature and heat fluxes on the different land-surface parameters, such as friction velocity, evaporative fraction, aerodynamic resistance and vegetation height. Finally, the dependency of surface state variables to the frequency of the forcing is analyzed.     

局地热力强迫与准定常大振幅扰动的形成

文中导得了包括热力强迫和耗散的非线性强迫ＫｄＶ－Ｂｕｒｇｅｒｓ方程,并作了数值求解。计算结果表明,热力强迫和耗散是孤波质量和能量变化的主要原因,耗散使孤波质量能量随时间指数衰减;热力强迫与地形一样,都能在强迫区产生定常孤波,但前者产生的上游扰动振幅更大,而后者产生的下游扰动更为明显;加热和地形一样都能使孤波发生位相漂移,减小其移速,阻挡孤波的移动,从而增加与孤波的相互作用时间;适当大小的耗散与热力强迫的组合迫使移动性孤波在强迫区附近来回振荡,大大增加与热力强迫的相互作用时间;在耗散与热力强迫同时存在的非线性系统中,移动性孤波与热力强迫的相互作用可能是产生阻塞等长生命周期的局地准定常系统的重要因子。     

Nonlinear kinetic energy interactions and their contributions to the growth and decay of atmospheric waves in the lower troposphere during summer monsoon, 1979

Summary Lower tropospheric (1000–500) hPa kinetic energy (KE), temporal variations of KE and nonlinear KE transfer of rotational and divergent flows and energy conversion between them, partitioning further into stationary and transient components in the Fourier spectral domain and the mechanism for the evolution of significant transient waves for the month July 1979 in the latitudinal belt 10° S–30° N are studied.Divergent zonal and eddy KE show their maxima at the lowest level 1000 hPa. Lower tropospheric monsoon motion provides a non-divergent level close to 850 hPa. The daily flow patterns bear little resemblence to the climatology over tropics at 500 hPa. Although the transient mode of synoptic scale waves is stronger than that of planetary scale waves they are comparable. Analysis of energetics over global tropics can get signature of transient activities embedded in the large scale system. Summer momentum flux in the lower troposphere is essentially associated with stationary planetary and transient synoptic scale waves. Waves 1, 3 and 6 are the most preferred transient waves. Divergent to rotational KE conversion is the most dominating mechanism for the maintenance of planetary and synoptic scale waves. All categories of waves contribute towards the maintenance of zonal flows. The primary source of energy for transient synoptic scale waves is the transient divergent rotational KE transfer whereas the interaction between zonal stationary and transient wave is likely to be secondary source. Transient KE and all transient interactions, stationary KE and all stationary interactions are found to be strongest at 500 hPa and 850 hPa respectively. Growth and decay of transient waves 1 and 3 are mainly controlled by divergent-rotational KE conversions whereas those of transient wave 6 are controlled by KE transfer due to zonal-wave interaction.With 13 Figures     

辐散风和瞬变的涡度通量的异常对定常波年际异常的强迫作用

研究了１９８２／１９８３年１２—２月对流层上层由辐散风和瞬变的涡度通量所产生的涡度源异常对定常波异常的强迫作用。结果表明，瞬变的涡度通量辐合的异常有抵消或耗散辐散风产生的涡度源异常的趋势；定常波的异常是在这两种强迫力的共同作用下维持的。同时还表明，对１９８２／１９８３年的情况，热带和赤道中东太平洋上的涡度源异常以及中纬度北太平洋上的涡度源异常都对太平洋／北美地区的大气环流异常起了重要的作用。     

On dynamically consistent eddy fluxes

The role of mesoscale oceanic eddies in driving the large-scale currents is studied in an eddy-resolving, double-gyre ocean model. The new diagnostic method is proposed, which is based on dynamical decomposition of the flow into the large-scale and eddy components. The method yields the time history of the eddy forcing, which can be used as additional, external forcing in the corresponding non-eddy-resolving model of the gyres. The main strength of this approach is in its dynamical consistency: the non-eddy-resolving solution driven by the eddy forcing history correctly approximates the original large-scale flow component. It is shown that statistical decompositions, which are based on space-time filtering diagnostics, are dynamically inconsistent. The diagnostics algorithm is formulated and tested, and the diagnosed eddies are analysed, both statistically and dynamically. It is argued that the main dynamic role of the eddies is to maintain the eastward-jet extension of the subtropical western boundary current (WBC). This is done largely by both the time–mean isopycnal-thickness flux and the relative-vorticity eddy flux fluctuations. The fluctuations drive large-scale flow through the nonlinear rectification mechanism. The relative-vorticity flux contributes mostly to the eastward jet meandering. Finally, eddy fluxes driven by both the eddies and the large-scale flow are found to be important. The latter is typically neglected in the analysis, but here it corresponds to important large-scale feedback on the eddies.     

经圈环流对定常波传播的影响

在一般斜压大气中，基本气流中包含经圈环流时，定常波传播不仅能穿过东风带，而且明显增强。在基流含有经圈环流的情况下，北半球中纬度地形强迫可引起低纬大气的显著响应，这表明经圈环流在中低纬定常响应的相互联系中起着重要作用；北半球中纬度热力强迫可产生类似北半球夏季季风环流的波列分布，这说明经圈环流在夏季季风环流的形成中起着一定的作用；在赤道东太平洋加热强迫情况下，在冬半球可引起ＰＮＡ型的定常波传播波列，而在夏半球却没有明显的ＰＮＡ特征。这表明经圈环流对冬、夏半球的定常波传播路径有着显著的影响。