Ferrel环流之新解

由于Ferrel环流与中高纬度存在强盛的西风带这一现代大气观测手段所证实的事实相悖,对其是否存在,及其环流形态一直存在着很大的争议.本文利用1998～2003年的NCEP/NCAR（National Center for Environmental Prediction/National Center for Atmospheric Research, 美国国家环境预报中心/美国国家大气研究中心）再分析资料（10°×10°,经/纬度网格）,根据北半球夏季（6～8月）太平洋地区（0°～60°N;160°E～120°W）的三维风场的基本特征,分析了北半球夏季太平洋地区平均经圈环流,特别是Ferrel环流的特征,发现Ferrel环流具有与已往研究不同的性质,并在此基础上提出了Ferrel环流新的概念模型,与过去的经典的环流概念模型相比能较好地描述高低空环流的基本特征,同时在考虑地球自转效应下,能够完满地解释中高纬度西风带的维持.     

强迫耗散作用下的Rossby包络孤立波及其相互作用

本文讨论了强迫和耗散对Rossby包络孤立波的影响，得到了在强迫和耗散共同作用下，当准共振条件和锁相条件满足时，包络孤立波从外场那里获取能量来克服耗散并形成稳定的锁相包络孤立波。本文还研究了在强迫和耗散作用下两个包络孤立波的碰撞相互作用，发现在某些参数下，两波碰撞后性质变化不大，而在另外一些参数下，碰撞后两波性质显著改变。     

积云凝结加热对海陆风的作用

本文用参数化方法研究积云凝结加热对海陆风的作用。第一部分是线性理论,在静力稳定度参数和湍流扩散系数为常数时,加热使风场的结构发生很大的变化。积云加热还起到修正静力稳定度的作用。第二部分是数值模拟,加热作用的主要贡献是使垂直速度增大,若海陆风是暴雨的触发机制,则积云凝结加热使这一机制加强。比较两部分结果,它们之间有一定的差异,但在风场的变化与加热场分布的对应关系上,两者是一致的。     

一个自组织气候模型

本文选择全球平均地表温度#AT#a和全球平均云量#An#a为状态变量。通过对气候系统中物理过程的研究与在气候意义上的合理近似，得到行星反照率α和大气有效发射率ε与状态变量的参数化关系，它们给出了气候系统内部几个重要的反馈过程。利用这些结果，建立起一个云和辐射相互作用的零维的非线性气候模型。在Hopf分支点附近，得到极限环的解析解，它们同数值解吻合得相当好，由解析解得到振幅，周期和位相差与太阳常数和CO2的近似关系，依此可估计它们在气候振荡中的作用，尤其，我们发现CO2的增加除有增温效应外，还能使气候振荡的振幅增加，这个结果意味着CO2的增加可能导致自然灾害周期性地出现或加剧。     

MAINTAINABLE MECHANISM OF MESO-β SCALE CONVECTIVE SYSTEM

By means of the Penn State-NCAR Mesoscale Model Version 5(MM5)with a horizontalresolution of 20 km.the maintainable mechanism of Meso-β scale Convective System(Mβ CS)hasbeen investigated on the basis of simulation of the temporal and spatial thermodynamics structureof the MβCS which occurred in Wuhan and its surroundings on 21 July 1998.The occurrence of thesignificant warm-core in the center of the MβCS happened in Changjiang River Basin between theMufu Mountain and the Dabie Mountain.To the southern side of the MβCS,there exist thesouthwest low-level jet(LLJ)and the vertical secondary circulation in the low and middletroposphere respectively.In respect to the northern of the MβCS,the northwest jet emerges in theupper troposphere,accompanied with cold and dry atmosphere downdrafts,resulting in anothersecondary circulation.The foregoing mentioned vertical wind shear provides a favorable dynamicalenvironment for the intensification and maintenance of the MβCS.Equally important,the latentheat release associated with the MβCS produces the warm center in the middle troposphere and thepressure falls.The pressure drop then accelerates air parcels toward the low leading to strongconvergence as well as the intensified convection,establishing a positive feedback between theconvection and the latent heat release,which is the thermodynamic mechanism of the developmentand maintenance of the MβCS.     

DISSIPATION EFFECT ON THE FLOW OVER MOUNTAINS

In the paper,the turbulent dissipation is considered in the model for studying the flow overmountains.The governing equation is a first order ordinary differential equation derived from analgebraic equation without dissipation case.The solution is sensitive to the upstream condition ofdissipation.The dissipation not only reduces the strength of discontinuity but also changes theproperties of the governing equation.In the paper,the qualitative characteristic features of thegoverning equation are discussed.The numerical results with super and sub-critical cases are alsodiscussed in detail.The results show that the turbulent dissipation is an important factor and is notnegligible.     

THE DYNAMICAL ANALYSIS OF THE STRUCTURE OF Β MESO-SCALE DOUBLE RAINBANDS IN MEIYU FRONT

In this paper, an idealized perturbation following the "surge-flow conceptual model" for typical Meiyu frontal structure is designed to explain the β meso-scale structure of rainbands in the Meiyu front using a non-hydrostatic, full-compressible storm-scale model including multi-phase microphysical parameterization. In addition, sensitivity numerical experiment on the vertical distribution of the ambient meridional wind is conducted to investigate the generation mechanism of β meso-scale double rainbands. The results of numerical experiments show that the cool and dry downdraft invading strengthened by the environmental aloft northerly wind plays a very important role to the generation and maintenance of the β meso-scale double rainbands. Moreover, the intensity and scale of the dry and cool downdraft invading are related to the intensity of the second circumfluence induced by mass adjustment when the acceleration of the westerly jet aloft occurs.     

移动性涡源与Rossby波

本文利用简单的一维正压涡度方程来分析与讨论涡源的强度变化及位置变化对于Rossby波的影响,得出了一些有兴趣的结果。     

变形场锋生条件下斜压锋区上对称波包的发展

文中用 WKBJ方法讨论了叠加在 Hoskins- Bretherton( 1 972 )变形场锋生模型背景上对称斜压波包的发展问题。在锋区斜压气流对称稳定的条件下 ( F2 N2 - M2 =q>0 ) ,大尺度变形场强迫、锋生环流的作用及锋生过程引起的稳定度参数 ( F2 ,N2 ,M2 )的个别变化也会对对称扰动的发展产生作用 ,变形场锋生和锋区环流的上升支下方有利于对称扰动发展 ,而锋区附近非地转垂直切变和稳定度参数的变化对扰动的影响则与对称扰动的结构有关。     

地形上空边界层流中低层锋面结构的理论研究Ⅰ:冷锋、均匀地转流

文中利用一个包含地形、边界层摩擦作用的二层锋面简化模型,讨论了地形、边界层对冷锋锋面结构、环流的动力学影响作用问题.冷锋的倾斜主要与冷锋暖区的地转流分布、锋面移动速度、锋面与地形的相对位置有关.当冷锋位于迎风坡时,其坡度减小,位于背风坡时,其坡度增大.在静止冷锋存在两类不同的环流系,即位于大气低层、地面锋附近的反时针环流系和远离地面锋的顺时针环流系.静止冷锋位于背风坡,其冷域中的这支闭合环流增强,范围增大,而位于冷锋界面上的环流转向点沿锋面上移,暖域中沿锋面的暖空气运动范围变大.当静止冷锋位于迎风坡时,结果相反.冷锋移动较慢时,其冷域远离地面锋的这支顺时针环流主体可被地形完全阻塞在迎风坡.当静止冷锋移离地形时,由于地形作用可在锋面暖域、地形下游形成一个背风槽.地形对锋区的垂直运动影响主要通过地形与边界层共同作用,改变锋区流场辐合辐散的分布及地形强迫抬升两条途径实现.由于边界层摩擦的辐合作用,在地面冷锋的前缘可形成一支范围较窄、强度较大的上升运动带,当冷锋位于迎风坡时,其强度增强,当冷锋位于背风坡时,其强度减弱.当冷锋位于背风坡时,在暖区沿锋面上升的暖空气运动范围增大,可以出现沿锋面相间隔的多个上升区.