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Geometrical Structure of Atmospheric Models and the Dynamical Basis of Weather Regimes and Blocking

大气模型的几何结构以及天气状况和阻塞的动力学基础

基本信息

批准号：
06640560
负责人：
ITOH Hisanori
金额：
$ 1.28万
依托单位：
Wakayama University
依托单位国家：
日本
项目类别：
Grant-in-Aid for General Scientific Research (C)
财政年份：
1994
资助国家：
日本
起止时间：
1994 至 1995
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-06640560/
关键词：
low-frequency weather regime blocking low-frequency oscillation chaotic itinerancy 分岐

项目摘要

Using a quasi-geostrophic model with realistic topography, we had shown that chaotic itinerancy is the dynamical basis of weather regimes. Furthermore, long-period oscillations exist in each attractor or attractor ruin, which is the dynamical basis of low-frequency oscillations. This year, we have made these phenomena more realistic and have clarified another kind of low-frequency variability.Changing a parameter in the model to unstable side, one regime (one attractor ruin, hereafter referred to as X) enlarges, while other regimes become obscure. These latter regimes are considered to correspond to real weather regimes. Amplitudes of low-frequency oscillations in X become large, which well explains real low-frequency oscillations.EOFs 1 and 2 have dominant low-frequency variabilities. These correspond to real teleconnection patterns. The reason why these modes are dominant is as follows. Spatial patterns of EOF1 well coincide with those of the first eigenfunctions of the equation system linearized with respect to the time-mean state. The corresponding eigenvalues are very small. In other words, these patterns strongly respond to forcing, and the time changes are small.Thus, EOF1 is selected among many other patterns. This characteristic is guaranteed by the fact that geometrical structure around the time-mean state is "flat". It is also shown that this characteristic is not accidental but necessary.

利用一个具有真实地形的准地转模式，我们证明了混沌巡游是天气系统的动力学基础。此外，每个吸引子或吸引子破产都存在长周期振荡，这是低频振荡的动力学基础。今年，我们使这些现象更加真实，并澄清了另一种低频变率。将模型中的一个参数改变到不稳定侧，一个区域（一个吸引子破产，以下简称X）扩大，而其他区域变得模糊。这些后者的制度被认为是对应于真实的天气制度。低频振荡的振幅变大，这很好地解释了真实的低频振荡，EOF 1和2的低频变化占主导地位。这些对应于真实的遥相关模式。这些模式占主导地位的原因如下。EOF1的空间模式与相对于时间平均状态线性化的方程系统的第一本征函数的空间模式相吻合。相应的特征值非常小。换句话说，这些模式对强迫的响应很强，并且时间变化很小，因此EOF1是在众多模式中被选中的。这个特性是由时间平均状态周围的几何结构是“平坦的”这一事实保证的。这一特性不是偶然的，而是必然的。