摘要
本文采用两层模式,初步地应用“时空同化”的自然观,引进空间不稳定性观点,把空间不稳定性和时间不稳定性结合起来,研究振幅随纬度变化的斜压行星波的存在范围和其稳定性;得出了稳定的和不稳定的斜压行星波及其空间不稳定判据,并对传统的斜压行星波不稳定理论和判据作出鉴定,重新提出了斜压行星波时间不稳定判据,并讨论其物理含义;还得出了高层和低层斜压行星波相互强迫振动的机制以及不同纬度间扰动振幅的关系。
In this paper,the two-level quasi-geostraphic model is used,the concept of assimilation of space and time is adopted,the idea of space instability is introduced and combined with time instability to study the effects of any disturbance introduced at an unidentified latitude to the general circulation.A general theory about the extent of existence of the planetary waves,the criteria of space and time instabilities and their physical implications,and the coupling of the high and low level planetary waves is presented.The extent of existence of the wave length of the baroclinic planetary waves is closely related to the velocity field and the vertical stratification.The more unstable the vertical stratification is,the shorter the length of the stable,moving planetary waves may appear will be.The vertical stability in the moist baroclinic atmosphere is much less than that in the dry baroclinic atmosphere,therefore,it is possible for stable,moving planetary waves of much shorter wave length to appear in the moist baroclinic atmosphere.Under the ordinary vertical stratification in the troposphere,it will be no stable,stationary ultra-long planetary waves.If the vertical strafication is as stable as that in the stratosphere,there will be stable,stationary planetary waves with wave length longer than 8500 km.The strength of the coupling effect of the planetary waves between the upper and the lower levels is determined by the vertical stability.If the vertical stratification is very stable,there will be little coupling effect between the upper and the lower levels.Under the ordinary stratification of the atmosphere,the planetary waves on the upper and lower levels are coupling to each other.The results of coupling are different for different baroclinic space stability.The criterion of the baroclinic space instability is just the 2nd degree polynomials of c in the classical theory of baroclinic instability.It expresses the relationship of the wave numbers along y direction of the baroclinic Haurwitz waves on the high and the low levels and the static stability parameter.The classical theory of baroclinic instabality is a spacial case of the theory considering both the space and time instability presented in this paper.The classical theory of baroclinic instability studies the special case of marginal space instability,and gives plausible results.The cieterion of time baroclinic instability is notδ<0,but c=c_(2).It implies that when c=C_(2),the frequency of the existing planetary wave kc equals to the frequency of the marginal stable baroclinic Rossby wave which may be considered as the characteristic frequency of the existing baroclinic atmosphere.Hence,some process similar to resonance happens,c becomes imaginary,i.e.c=cr+ici,cr=c2 ci depends on space stability and d.The ideas of space and time baroclinic instability,and stable and unstable planetary waves might help in explaining the observations and solving the discrepancy that the planetary waves are considered as neutral waves in Rossby’s and Haurwitz’s theories,while they are considered as waves with wave length of maximum instability in the theory of baroclinic instability.
作者
谢义炳
Xie Yi-bing(Yi-Ping Hsieh)(Department of Geophysics,Beijing University)
出处
《气象学报》
1981年第1期44-58,共15页
Acta Meteorologica Sinica
