深厚和浅薄球面大气中的斜压行星波

本文在包括对流层—平流层—中间层(0—80公里)的半球及全球大气模式中,求解特征值及特征函数问题,得到夏季及冬季纬向平均基流中发展型行星波及天气尺度波的增长率、相速度及空间结构。结果指出,在冬季环流中存在三种不同结构及相速的发展型波动:1.行星尺度的准稳定Green波(波数1—2),其振幅在平流层中上部达到极大;2.深厚而准稳定的Char-ney波(波数3—4),其振幅在对流层中达到极大;3.天气尺度的移动性Charney波,这是一些波数5—9的对流层波动。在夏季环流中存在两种发展型波动:中间层内自东向西移动的波动1—4及对流层中自西向东移的天气尺度波动。这些发展型波动的结构、移速及出现层次与实际大气中的瞬变波有相当好的对应,由此推论,深厚球面大气基本流的动力不稳定可能是激发这些波动的重要机制。此外,深厚模型与浅薄模型的对比分析指出,以行星波为对象的数值模式必须包括对流层和平流层,简单的对流层模式会严重歪曲行星波的结构与移速。

THE BAROCLINIC PLANETARY MODES IN DEEP AND SHALLOW SPHERICAL ATMOSPHERIC MODELS

The growth rate, phase speed and the spatial structure of the growing planetary and synoptic waves in winter and summer zonal mean flows have been investigated by the eigenvalue-eigenfunction technique based on a hemispheric and a global model including the troposphere-stratosphere-mesosphere (0-80km). The results show that the winter basic flows are able to generate three types of growing waves:the quasistationary planetary Green modes (wavenumber m=1-2),the deep Charney modes (m=3-4) and the tropospheric propagating Charney modes (m=5-9).In the summer basic flow, 2 types of growing waves exist:the westward propagating waves in the mesosphere (m=1-4) and the eastward propagating waves in the troposphere (m=5-7).The results compare with observation favorably, suggesting that a mechanism of dynamic instability of a deep atmosphere may be responsible for the observed transient planetary waves. By comparison between the results of the deep model and a few shallow models, it is concluded that a numerical model of planetary waves should at least extend to the stratopause. The traditional tropospheric models woule seriously distort structures and phase speeds of the planetary waves.