长波近似与大气中的线性与非线性Rossby波

大气运动中,在x,y方向的水平尺度L_xL_y往往是不同的。特别是当L_y相似文献   

半地转气流的动力学特征

利用地转动量或半地转的假定,可以引入地转坐标而使问题的处理得到了简化,但是,地转坐标下的解还需经过转换而回到原来的坐标,即物理坐标.在本文中,给出了从地转坐标回复到物理坐标的一种近似方法,利用此方法讨论了Eady 型斜压波动与锋生过程的动力学特征,并探讨了半地转气流的作用。     

准地转演变过程中的多时态特征

本文利用大气运动中多时态的概念,对准地转运动的物理特征进行了分析与研究,指出在不考虑非绝热及湍流摩擦等作用时,准地转运动中所出现的多时态或多阶段的特征,是与运动的水平尺度密切相关的.文中还对正压与层结大气中的准地转运动的特征进行了分析与比较,并讨论了二者差别的原因.     

论赤道地区的大气边界层

本文给出了赤道地区线性Ekman层的控制方程及其解答,指出如果考虑了边界展与自由大气相互作用的物理机制,则大气的位势高度不应该完全独立于边界层.利用这一观点,可以对高度场给以一定的合理约束,使自由大气与边界层内之解具有合理的连续分布。这样,便可克服在临界纬度上垂直速度无限增大的困难。同时,还得到了在临界纬度上,边界展的风速解不呈Ekman螺线的新的结果。利用Mahrt所提出的充分混和的条件,来验证这一结论,得出相同的特点,这也说明所得出的结果具有一定的合理性的。     

DYNAMICS OF SEMI-GEOSTROPHIC FLOW

Under the assumption of geostrophic momentum/semigeostrophic flow, the problem willbe simplified by introducing the geostrophic coordinate. However, the solution in geostrophiccoordinate should be converted into the original one (ealled the physical coordinate). This isan important step to lead the final solution of the problem. In this paper, an approximationmethod which can be used for 3-dimensional problem is developed and the problem of baro-clinie instability of Eady type wave is studied.     

正压大气中波动共振与能量变化

本文讨论了正压大气中不同尺度的波动发生共振时能量变化的特点,指出在非线性问题中,解的形式与初值具有非常密切的关系。在一般情况下,扰动的能量及其变化是有界的,是具有周期性的,但在某一合适的条件下,其中的一个波动得到充分的发展,而其余的波动渐趋消弱,最后消失,这些现象在线性处理中是得不到描述的。     

Ekman动量流的动力特征与锋生

本文在Ekman动量近似下,推得边界层动力学中的4个伪守恒关系式,且引入Ekman坐标,使问题简化,Ekman坐标中运动呈经典的Ekman流,然后给出了由Ekman坐标中的解回复到物理坐标中的一种近似方法,这种回复过程能反映出系统的非线性,利用这种方法讨论了边界层摩擦对Eady型斜压波及锋生过程的影响。结果表明,由于Ekman动量流具有一定的非地转性,造成了边界层中的锋生,但又因边界层摩擦具有一定的耗散作用,与自由大气相比,边界层中出现间断的时间要增长,锋生过程要减弱,Ekman动量流具有二重性。     

Nonlinear Rossby Waves and Their Interactions (Ⅰ) ——Collision of Envelope Solitary Rossby Waves

By using the multiple-scale perturbation method a set of equations which describes two interacting nonlinear Rossby waves in the barotropic atmosphere is derived. The equations are used to study the collision of two envelope solitary Rossby waves. It is found that for a range of parameters, the collision interactions are envelope soliton-like in that the properties of the two envelope solitary waves change very little. For other parameters, new "inelastic" effects are observed, including speed changes, fission of envelope solitary waves and energy dispersion. It is also found that despite of the complexity of the interacting process, the energy of each wave is conserved.     

ATMOSPHERIC BOUNDARY LAYER IN EQUATORIAL AREA

A system of linearized equations which describe the motion in the tropical boundary layer and their solutions are given in this paper. If the interaction between the boundary layer and the free atmosphere is taken into consideration, the potential height of the free atmosphere cannot be entirely independent of the character of the boundary layer. From this point of veiw, the continuous and bounded solutions of the boundary layer are obtained by imposing some suitable conditions to the field of potential height and thus the difficulty that the vertical velocity at the critical latitude tends to infinity can be overcome. Furthermore, a new result that the variation of the wind with height in the boundary layer at the critical latitude is not in the form of classical Ekman spiral is obtained. And this is also supported by the result obtained under the assumption of the so-called well-mlxed condition proposed by Mahrt.     

LONG WAVE APPROXIMATION, LINEAR AND NON-LINEAR ROSSBY WAVES

The length scales L_x, L_y in x and y directions respectively are not in the same magnitude usually. For instance, L_x>L_y. This is called the long wave approximation and can be used to simplify the problem. The KdV equation can also be easily derived under this approximation. In this paper the physical foundation of the application of this long wave approximation to the non-linear Rossby wave is analysed The results show that the parameter (L_y/L_x)~2 which denotes the degree of anisotropy in the length scale is an important factor. As it reduces, the motion tends to higher frequency. For the low-latitudes, it is also easy to deriveKdV equation with the same approximation for non-linear Rossby wave. The characteristic features of the non-linear Rossby wave in the low latitudes are similar to those in the midlatitudes.