包括大地形作用的大气环流模式的长时期性状

本文用一个两层斜压原始方程模式研究了包含大地形作用的大气环流模式的长时期性状.首先以刚体旋转为初值条件,用绝热无摩擦的两层斜压模式作了一个月的数值积分,研究了模式大气对纯粹地形强迫的响应.结果发现积分至第15天以后,中纬度西风渐弱,使得积分前期由地形强迫产生的槽脊难以辨认.本文通过不同模式之间的比较,对500hPa高度场上的球谐分析以及对动量方程的诊断,认为它是一种确定的动力学现象,而不是计算紊乱.在模式中引入纬向对称型加热和地面摩擦过程后,即使将模式积分长达5个月以上,由地形强迫激发的扰动所形成的槽脊仍可长久地维持,但它不是简单意义下的定常波,位相分析表明只有二波分量近似驻波,与转盘实验结果相似.

Long-term behavior of a GCM including large scale topography

A series of experiments is performed to investigate the behavior of a twolayer general circulation model in long-term integration . Firstly , the adiabatic frictionless version of the model is run to study the response of a spherical free atmosphere to pure orographic forcing . The result shows that the ridges and troughs forced by the topography can not be maintained more than 20 days . Then some possible causes for that are studied by using diagnostic analysis . Finally , a zonally symmetrical diabatic heating and a simple friction are introduced into the model and a 150 day integration with the model is carried out. The analysis of time-averaged 500 hPa height reveals that the mountain-forced ridges and troughs still exist even in the last 15 days of the period . A phase analysis indicates that only the component with zonal wave number two seems to be quasi-steady , while the other components are transcient.