外强迫作用下正压大气非线性特征数值模拟  

Numerical modeling of non-linear characteristics for barotropic atmosphere with external forcing

作　　者：汪萍[1] 戴新刚[1] 

机构地区：[1]中国科学院大气物理研究所

出　　处：《物理学报》2005年第10期4961-4970,共10页Acta Physica Sinica

基　　金：中国博士后基金(批准号:2004035074);王宽诚博士后工作奖励基金资助的课题.~~

摘　　要：在两种边界条件下用正压大气非线性位势涡度方程模拟了强迫、耗散和非线性共同作用下大气运动的若干特征.在南北两端为齐次边界条件时,单纯的热力强迫下只出现了波状定常解;在只有经向加热和波状地形共同强迫下出现了在两种基本流型之间振荡的准周期解,十分类似于旋转地球上大气运动的纬向和经向流型之间的准周期循环,前者对应于强的西风环流,后者对应于弱西风流型.在周期边界条件下,弱的下垫面加热导致定常解,较强的加热强迫可以得到周期解.尽管下垫面的波状地形也能强迫一个类似的准周期振荡,但弱西风流型是对称的,不像大气中的弱西风流型.因此,在周期边界条件下用低阶截谱模式求出的解析或数值解,不一定适合描述中高纬度大气的非线性动力特征.Some characteristics of barotropic atmosphere are illustrated by numerical modeling, basing on a potential vorticity equation with forcing, dissipation, and non-linear interaction. For the barotropic potential vorticity equation （named the barotropic model） on a β-plane channel its solution is a stationary, wave-like pattern under a certain thermal forcing, while a quasi-periodic oscillation between two essential flow patterns appears if north-south thermal heating and wave-like topography are added as the model forcing. The oscillation has a period about 15d, very similar to atmospheric index cycle in middle and high latitudes. The low-index pattern corresponds to a blocking flow, whereas the high index one is an intensive westerly flow. More oscillation solutions are expected when the equation is under periodic boundary condition with a strong thermal forcing, and a similar quasi- periodic solution can be obtained, which also results from a wave topography forcing. However, its low index pattern is symmetrical, and different from the blocking pattern produced by the β-plane model. When the heating forcing becomes weak, there also exists a stationary solution. Therefore, the characteristics of atmospheric index cycle may not be soundly manifested by an analytical solution or numerical solution under periodic boundary condition using low-order spectrum method that approximates the barotropic model in the β-plane channel.

关 键 词：正压大气 热力强迫 地形起伏 周期解 准周期振荡 非线性特征 数值模拟 强迫作用 齐次边界条件 周期边界条件 

分 类 号：P401[天文地球—大气物理学与大气环境]