波流相互作用的大气系统中振荡模态的分析

Analysis of vacillation mode in the atmosphere system with interaction between the basic flow and the waves

把经验模态分解(EMD)方法用于波流相互作用的大气动力系统,对不同系统状态的流函数解序列求其本征模态函数(IMF)分量,分析系统状态与IMF之间的关系,揭示流函数的振荡结构。结果表明:随着系统的复杂性增大,构成解序列的IMF分量的个数相应增多。对于系统的定常态(Hadley流),每个流函数Ψ分量的各个IMF分量都趋于零均值线;对于周期态(Rossby流),Ψ分量由1个周期性的高频IMF分量构成;对于振荡态,Ψ分量主要由2—3个较高频IMF分量构成;对于非周期流,Ψ分量由多个非周期的IMF分量构成;对于周期-非周期状态,其本征模态有的有周期性,有的没有周期性。低频IMF分量表现Ψ序列的长时间尺度的变化。

Empirical mode decomposition （EMD） method is applied to the atmospheric dynamical system that interacts between the basic flow and the waves, the intrinsic mode functions （IMF） are separated to the solution series of the stream function to the different system states, and the relation between the system state and the IMF is analyzed, and realized streamfunction vacillation structure. The results show that along with the more complicated system, the IMF＇s numbers which are formed of the solution series correspondingly increases. As for the Hadley flow, each IMF of all components of the stream function Ψ is all going to zero equal line; as for the Rossby flow, Ψ components are mainly formed by a high frequency IMF with periodicity; as for the vacillate state, Ψ components are mainly formed by two or three high frequency IMFs with periodicity; as for the non-period stream, Ψcomponents areformed by many IMF＇s with no period; as for the multi period and non period states, the same compnent can be formed by period and nonperiod vacillation waves. Low frequency IMF components show the long time change of Ψ series.