The Research On The Evolution And Application Of The Baroclinic Instability Theory

The first half of Twentieth Century is considered as one of the most rapid development period of atmospheric science.A lot of theoretical foundings in atmospheric sciences have been established in this period.Baroclinic instability theory is one of the most representative theoretical achievements of the period.It is a fundamental instability mechanism for large scale atmospheric,especially for high and middle latitudes.Baroclinic instability theory is also an important progress in the dynamic meteorology after the long wave theory being set up.Besides,it has been successfully used as a starting point and theoretical basis to simplify the atmospheric movement equations,leading to the first successful numerical weather prediction(NWP).Although the theory has been put forward for nearly 70 years,it is still important for modern weather forecast.Therefore,it is necessary to systematically tease out the course of the baroclinic instability theory.The historical contributions and shortcomings of the leading scientists are also needed to evaluate objectively,in order to help us to come to a better understanding the context,historical enlightenment and its realistic meaning of the baroclinic instability theory.The theory is established by the pioneering work of Charney.Many other scientists such as Eady and Jaw(???)also contribute to it.Based on the brief introduction to the background of baroclinic instability theory,this paper focuses on baroclinic instability theory and reviews its application contributions by Charney,Eady and Jaw.The characteristics of the three scientists have been analyzed.By comparing their personal experiences and research ideas,this paper summarizes the reasons why Jaw could not build the theory one year ahead.Based on the development of the theory,a brief review on the promotion of the three aspects are given,which are the stability of atmospheric motion in large scale,the interaction between wave and flow,and numerical weather prediction.Finally,three weather cases are analyzed in order to verify the significance of baroclinic instability theory.This research focuses on the analysis of the reasons for Jaw's failure by in contrast of the representative works of the three scientists: Jaw's research is one of the earliest in view of baroclinic instability.A critical wavelength of the instability was given,and the energy conversion and the possible influence on atmospheric circulation were also analyzed.His research was undisputedly progressive at that time.However,the vertical movement were not be considered in his study,which led to the final failure.And because of this reason,some of the highlights in his paper were neglected.In 1947,by the wave filtering and scale analysis,Charney simplified the equation of atmospheric disturbance,so that it could be solved.He deduced the criterion of the stability,and established the baroclinic instability theory.As its by-product,the QG theory made the numerical weather forecast become successful for the first time.In 1949,based on the work of Charney,Eady obtained a more simplified model.Comparing the personal experience,educational background,research ideas and thesis characteristics,it can be seen that these have an important impact on innovation research.However,Chinese scientists are not dominant in all aspects,it is not easy that they put forward key problems first in atmospheric dynamics,for example “baroclinic instability”.There historical contribution should be appreciated and respected.The baroclinic instability theory affects on the weather system.Based on a detailed analysis of the promotion of the theory to related fields,three cases of extratropical cyclones are selected in order to make a concrete analysis.The first one formed in the ocean in winter,the second one formed in the continent in summer,and the last one is a passing cyclone which formed in spring.Using the NCEP/NCAR 1°×1° reanalysis data,three extratropical cyclones' characteristics are analyzed in three stages of the birth,development and maturity.For example,height field and temperature field at 500 h Pa,as well as the vertical profiles of potential height,temperature,vertical velocity and horizontal divergence.The characteristics are similar to Charney's and Eady's results.Finally,based on the comparison of the three scientists' papers and on cases analysis,this paper try to put forward the inspiration and significance of the baroclinic instability theory for the scientific research innovation:(1)the progress of the discipline is largely dependent on the development of other disciplines or technologies;(2)The emergence of a scientific result can not be separated from the accumulation and the foundation of the previous research results;(3)There is a strong uncertainty in scientific research,sometimes,“by-product” of scientific research can play a bigger role in promoting the development of the subject.