斜压不稳定理论的发展历程分析

An analysis of the development of baroclinic instability theory

斜压不稳定理论是中高纬度地区天气尺度扰动生成和发展的机制,是继长波理论之后大气动力学上的又一重大进展,对现代天气预报具有重要的指导意义。按照斜压不稳定理论发展的时间脉络,阐述了赵九章、查尼和伊迪在斜压不稳定方面开展的研究工作,分析了3位科学家各自的研究特点及历史贡献。赵九章1946年发表在《Journal of Meteorology》上的论文,最早提出了"斜压不稳定"这一概念,给出了不稳定的临界波长,并阐述了在不稳定扰动情况下能量的转换,以及不稳定波对大气环流带来的可能影响,尽管得出的不稳定临界波长与观测差别较大,但其对波-流相互作用的讨论在当时是超前的。查尼于1947年采用滤波和尺度分析等方法,将大气扰动方程简化为一个可以求解的系统,推导出大气稳定状态的判据,建立了斜压不稳定理论,其结果与实况比较接近;并据此把准地转模式成功应用于数值天气预报实践中,促使数值天气预报获得首次成功。1949年,伊迪在查尼研究工作的基础上通过合理的简化方法,得到了更为简洁的模型。最后,通过对比他们的研究思路,重点分析了赵九章未能使得斜压不稳定理论提前一年建立的原因:由于其研究思路始终局限在大气水平运动上,忽略了斜压系统发展中散度项的贡献,因而未能抓住天气系统发生、发展的本质,致使其最终与斜压不稳定理论的成功建立失之交臂,其论文本身存在的一些亮点也因此被后人忽视。

Baroclinic instability theory reveals a fundamental instability mechanism for large scale atmospheric perturbations,especially over the middle and high latitudes.It is also an important progress in the dynamic meteorology after the establishment of long wave theory,and still important for modern weather forecast.This paper focuses on the evolution of baroclinic instability theory and reviews the contributions by Charney,Eady and Jaw.Jaw＇s research is one of the earliest studies in view of baroclinic instability.A critical wavelength of the instability was proposed,and the energy conversion and its possible influence on atmospheric circulation were also analyzed.His research was undisputably progressive at that time.In 1947,by the wave filtering and scale analysis,Charney simplified the equation of atmospheric disturbance to make it able to be solved.He deduced the criterion for the stability,and established the baroclinic instability theory.As its by-product,the quasi-geostrophic theory made the numerical weather forecast to be successful for the first time.In 1949,based on the work of Charney,Eady obtained a more simplified model.By comparing their research ideas,this paper summarizes the reasons why Jaw could not build the theory one year ahead：the vertical movement and the essence of the genesis and development of weather system were not considered in his study,which led to the final failure.And because of this reason,some of the highlights in his paper were neglected.