A Numerical Study on the Maintenance of Weather Regimes and their Transitions

天气状况维持及其转变的数值研究

• 批准号: 06640558
• 负责人: YODEN Shigeo
• 金额: $ 1.34万
• 依托单位: KYOTO 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-06640558/
• 关键词: weather regime; quasi-steady state; finite-time Lyapunov stability; predictability; Life cycles of extra-tropical cyclone; double-jet; single-jet; global atmospheric model; PV-rheta method; 低次モデル; カオス; ホモクリニック軌道

The main purpose of the present study is to clarify the mechanisms of the maintenance of weather regimes and and transitions between them by using idealized full-nonlinear numerical models. Our final goal is a complete dynamical understanding of low-frequency variability in the troposphere in the light of multiple weather regimes and their transitions.A highly-truncated barotropic model of the atmosphere introduced by Legras and Ghil (1985) was used to study the dynamical structure of weather regimes and their relationship to the temporal variation of predictability. The model is a low-order spectral model of 25 variables which includes the effects of zonal-flow forcing, dissipation and surface topography. Dynamical properties of the attractor of the model was investigated to show the role of quasi-steady states (i.e., weather regimes). Intensity of the zonal-flow forcing was changed as an experimental parameter. A finite-time Lyapunov stability analysis was also done for several examples of the attractors to show the relationship between the quasi-steady states and predictability.A global primitive-equation model of the atmosphere was used to study nonlinear interactions between mean zonal flow and baroclinic disturbances. Internal non periodic variation is found in long-time integrations of the model under a perpetual condition. The variation is characterized by irregular transitions between two preferred regimes of double-jet and single-jet of mean zonal flow. A PV-rheta analysis was done for two extreme periods of these regimes and two different patterns of the life-cycles of extra-tropical cycles were obtained in the corresponding regimes. A statistically significant relationship was also obtained between the zonal flow regimes and the patterns of the extra-tropical cyclones.

本研究的主要目的是通过理想化的全非线性数值模式来阐明天气系统维持和转换的机制。本文利用Legras和Ghil（1985）提出的一个高度截断的正压大气模式，研究了对流层低频变率的动力结构及其与可预报性时间变化的关系。该模型是一个包含25个变量的低阶谱模型，其中包括带状流强迫、耗散和表面地形的影响。研究了模型吸引子的动力学性质，以显示准稳态（即，天气状况）。改变带状流强迫的强度作为实验参数。对几个吸引子实例进行了有限时间李雅普诺夫稳定性分析，揭示了准稳态与可预报性之间的关系。利用全球大气原始方程模式研究了平均纬向气流与斜压扰动之间的非线性相互作用。在永久条件下，模型的长时间积分存在内部非周期变化。变化的特点是不规则的过渡之间的两个首选制度的双射流和单射流的平均纬向流。对这两个极端的周期进行了PV-Rheta分析，得到了两种不同的热带外循环的生命周期模式。纬向流场与热带气旋型之间也存在着统计上的显著关系。

项目成果

余田成男: "カオスと気象予測" 科学. 65. 305-313 (1995)

N. Yoda：“混沌与天气预报”科学 65. 305-313 (1995)。

Shigeo Yoden: "Chaos and weather prediction (in Japanese)" KAEAKU. 65-5. 305-313 (1995)

Shigeo Yoden：“混沌与天气预报（日语）”KAEAKU。