斜压基流中的非线性中尺度重力惯性波

本文使用行波法分析求解y-z平面上的二维流体非线性动力学方程组，在斜压基流的背景场下讨论了CISK加热影响下的粘性非线性椭园弦波以及重力惯性弧立波的特征，一般情况下，中高纬度地区层结较稳定在呈气旋性切变的强斜压性基流背景场之中，CISK加热系数ηb较小而ηd较大影响下的重力惯性弧立波表现为陡而范围小的特征，也就是说，在较小的中尺度范围内，集中产生较为强烈的灾害性天气。     

近几年中国大气动力学的主要进展

１０年来，尤其是最近几年来，中国科学家在动力气象学以及新兴发展起来的气候动力学的研究方面取得了明显的进展，许多成果得到国内外专家的重视和好评。本文就主要的几个方面作一概括性的介绍，以促进中国动力气象学和气候动力学研究的进一步发展。     

近百年来热带太平洋海温年际及年代际时间变率特征的诊断研究

年际及年代际时间变率是当代气候研究的重要问题之一 ,通过对近百年热带太平洋海温资料做子波分析发现 ,2 0世纪 50年代以来的海温升高及频繁发生的 ENSO事件伴随着海温年代际时间尺度背景场的明显改变 ,同时还研究了其年代际及年际时间尺度时间变率特征。     

大气中CO_2浓度增加对我国气候的影响

本文利用一个全球九层大气环流模式，对大气CO2浓度倍增以及CO2浓度倍增同时海温升高进行了两个数值试验。主要分析了CO2浓度增加对我国夏季气候的影响。在仅仅考虑CO2浓度倍增的情况下，我国大部分地区气温升高，尤其在西北地区升温最多，但是长江中、下游地区则是降温。考虑CO2浓度倍增后大气对海洋的感热作用使海表温度上升，所得结果基本相同，但升温幅度增大。大气中CO2浓度倍增后，我国降水分布有所改变，西北地区更加干燥，沿海地区更加湿润。     

Numerical Study for Characteristic Change of Asian Summer Monsoon Circulation and Its Influence Mechanism during the EI Nino Period

In this paper, the relation between Asian summer monsoon circulation and sea surface temperature anomalies over equatorial central-eastern Pacific is investigated by using a global spectral model. This model has nine layers in the vertical and the model variables are represented in the horizontal as truncated expansions of the surface spherical harmonics with rhomboidal truncation at wave number 15. The model involves comparatively complete physical processes and parameterizations with mountains.Using the above model, two experimental schemes are designed, namely control case and anomalous sea surface temperature case. The above two schemes are respectively integrated for forty days and the simulated results are obtained from the last 30-day averaged simulations.The simulations show that positive SST anomalies over equatorial central-eastern Pacific weakens Indian monsoon circulation,decreases precipitation in Indian sub-continent whereas it intensifies East Asian monsoon circulation and increases preci     

DIAGNOSIS OF LOW FREQUENCY COMPONENT OF ENSO VARIABILITY—PART Ⅰ:GLOBAL-SCALE DYNAMIC CHARACTERISTICS OF THE COMPONENT

Composite investigation is performed of global dynamic characteristics of >3—4-year period low-frequency oscillation in ENSO variability of air-sea coupling in the context of monthly mean wind andSSTA.Evidence suggests that the horizontal(vertical)anomaly circulation at tropical latitudes(equatorial)exhibits their evolution to be,in substance,a kind of low-frequency wave slowly travel-ling eastward,featured by wave number 2 moving along the equator and zonal wind swiftly decayingoff the equator in relation to divergence/convergence:the time that the low-frequency wave takes tomove around the equator in its halfway is precisely the period of the ENSO low-frequency component(LFC)(approximately 4 years);the ocean also displays corresponding response to the component.     

THE SENSITIVITY OF THE NUMERICAL SIMULATION TO OROGRAPHY SPECIFICATION IN THE LOWRESOLUTION SPECTRAL MODEL-PART II: IMPACT OF THE SMOOTHED OROGRAPHY AND RIPPLES ON SIMULATIONS

In order to investigate the impact of the smoothed orography and the spurious orographic ripples on simulations in the low-resolution spectral model, three different numerical tests, that is, the unsmoothed orography scheme, the smoothed orography scheme and non-ripples scheme are performed. In this paper, the model used by us is the same as Part I except for orographic specification.The results from simulations indicate that, as far as the climatic simulation is concerned, some aspects of the simulated stationary disturbances, zonal and meridional wind, temperature and precipitation in the low-resolution spectral model with properly smoothed mountains are significantly improved, especially in winter hemisphere.The deep ripples in the model with the unsmoothed orography produce spurious high pressure regions at the surface with subsidence, and suppress rainfall, causing an unrealistic splitting of the precipitation area in northern winter and summer. Removal of the deep ripples by using the special proc     

一次梅雨锋暴雨过程的 β 中尺度对流系统发展机理的数值研究

20 0 2年 6月 18～ 19日在湖北省发生的一次中尺度降水过程主要是由一个中尺度对流云团的活动造成的 ,且该中尺度对流云团在不断东移的过程中分裂成两个 β中尺度对流云团。文中使用中尺度非静力模式MM5对该次暴雨过程进行了数值模拟 ,研究它的发生发展机制。模式很好地模拟了造成该次强暴雨的中尺度对流系统的整个发展过程 ,模拟的降水分布与实况比较接近。分析模拟结果发现 ,中尺度对流系统在不断东移的过程中 ,受高层的辐散性流场的抽吸作用和低层的对流不稳定而发展加强 ;受地形的作用而分裂成两个对流单体 ;最后由于中高层水汽凝结降落后造成的水汽不足 ,高层的辐散气流明显减弱变得无组织和下沉气流的影响对流系统开始衰亡。通过以上的分析给出了引起该次梅雨锋暴雨过程的中尺度对流系统的发展演变模型。     

β中尺度暴雨系统发生发展的一种可能物理机制 II.涡旋Rossby波的形成

使用二维中尺度横波型扰动的动力学方程组,探讨了该扰动的各种物理量场分布特征以及能量来源。结果表明,这种横波型的天气系统中扰动气压p′和扰动涡度ζ′在水平x方向上处于同位相或者反位相,扰动散度D′和扰动垂直速度w′在水平x方向上也处于同位相或者反位相,而扰动涡度ζ′与扰动散度D′在x方向上传播的位相相差π/2,只不过它们在垂直方向z上的分布结构有所不同。局地区域扰动发展的总能量来源主要是来自于平均场的有效位能和平均场的基流动能。最后,利用横波型扰动的总涡度守恒方程对涡旋Rossby波形成的物理机制做出了解释,并且提出了梅雨锋暴雨中β中尺度暴雨系统发生发展的一种可能物理过程。采用中尺度MM5模式的数值试验结果,也得到了与动力学理论上相一致的结论。