中高纬大气30—60天低频振荡的一种动力学机制

本文着重考虑非均匀基本流的正压局地不稳定性，研究中高纬低频振荡产生的动力机制。基本流是取1980年冬、夏300 hPa的位势场。结果表明正压局地不稳定性能较好地解释中高纬大气30—60 d天振荡。这似乎表明，低频振荡是大尺度大气运动和扰动相互作用的一种固有特征，而不是外源强迫的结果。本文还讨论了适于激发季节内低频振荡的基本流场。初值问题的研究发现中高纬大气30—60 d振荡呈纬向三波模态发展，与初始扰动和基本气流的冬、夏差别无关。

A Possible Dynamic Mechanism of the Atmospheric 30-60 Day Period Oscillation in the Extratropical Latitude

In this paper, the barotropic local instability of the inhomogeneous basic current is emphasized to study the dynamic mechanism producing the intraseasonal variability in the extratropical latitude. The mean geopotential height fields on 300 hpa for winter and summer of 1980 are adopted as the basic currents respectively. The results indicate that the barotropic local instability rather satisfactorily accounts for the atmospheric 30-60 day periodic oscillation at the middle and high latitudes. This seems to show that the low frequency oscillation is an intrinsic characteristic of the large scale atmospheric motion interacting with the perturbation rather than the consequence of the external forcing. Moreover the basic currents accommodated to the triggering of the intraseasonal oscillation are discussed. The investigation on the initial value problem reveals that the atmospheric 30-60 day periodic oscillation develops stably on the zonal 3-wave mode, and is independent of the initial disturbance as well as the discrepancy of the basic currents between winter and summer.