摘要
以球面正压涡度方程为数学模型,建立了线性和非线性的数值积分模式,通过在模式中设置不同的基本流场和初始扰动场,研究基流和初始场对扰动发展的作用,揭示在球面正压大气中扰动发展的动力学机制。数值试验结果表明:在线性模式中,扰动的移动和发展与基流的分布有着很密切的关系,基流影响着扰动纬向传播的速度和方向;在非线性模式中,当基流稳定时,扰动的移动以及传播与线性模式的结果相同,但与线性情况的最大区别在于,此时扰动能量的增长存在上限。同时发现,扰动的发展既依赖于基本气流的分布,也依赖初始扰动的结构;南海夏季风爆发前后的基本流场是正压不稳定的,且这种不稳定在季风爆发时达到最强,这可以成为季风爆发的动力学解释。
Using the normal mode method, people can get the necessary condition and the increase rate of the linear instability. But, the normal mode method only can be used to deal with the small disturbance of single wavelength, and at the beginning of the disturbance evolvement. When the shearing do not exist in the basic stream fields, all the diagnostic waves are discrete spectra, in the circumstances the normal is reasonable. As there are shearing in the basic stream fields, the continuous spectra must be considered. In fact, the space structure of the disturbance correlates with time. In the finite period of time, the initial disturbance fields notably affect the produce and evolvement of disturbance. In this paper, the simple linear and nonlinear integral models are established by predigesting the spherical barotropic vorticity equation. The integral results of the spherical barotropic vorticity equation can be gotten using the linear and nonlinear integral models. The mechanisms of disturbance evolvement are investigated through setting different basic stream fields and initial disturbance fields in the integral model. The 40-year mean disturbance evolvement before and after ~M （the South China Sea Summer Monsoon） onset is also calculated by using the linear and nonlinear integral models. In the spherical barotropic vorticity equation, the motion and evolvement of disturbance field depend on the configuration and distribution of the basic stream field. The result of numerical experiment shows that： （1） There is the special relationship between the basic stream field and the motion and evolvement of disturbance field. Configuration of the basic stream field impacts the velocity and direction of the latitudinal and longitudinal transmittal. The large-scale disturbance moves westward, contrarily, the small-scale disturbance affected by the basic stream field moves eastward. （2） The energy transformation is related to the distribution of the basic stream field and the structure of the initial disturbance.
出处
《大气科学》
CSCD
北大核心
2007年第5期898-908,共11页
Chinese Journal of Atmospheric Sciences
基金
国家自然科学基金资助项目40233027
关键词
球面正压大气
扰动
基流
线性和非线性模式
南海夏季风
扰动演变
正压不稳定
spherical barotropic atmosphere, disturbance, basic stream field, linear and nonlinear model, barotropic instability, evolution, the South China Sea Summer Monsoon （SCSSM）
