基于动力学模态分解的200 hPa急流模态特征分析

提出基于动力学模态分解（Dynamic Mode Decomposition，DMD）的大气运动数据分析方法，目的是改进对大气运动特征的认识。首先，采用DMD方法对200 hPa急流运动流场进行模态分析，从中得到了急流天气系统运动变化过程中的主要模态和对应频率以及模态随时间衰减/增长等信息。这些模态是对流场演化特征的低维描述，反映了蕴含在流场中的动力学特征，可用于实现高维复杂流场的低维近似表示。其次，建立了200 hPa急流运动流场演化的动力学降阶模型，能够重构和预测急流运动流场的动态发展过程。结果表明：通过对前6阶主要模态所包含的流场信息进行对比分析，DMD方法成功捕捉到了200 hPa急流运动流场不同尺度的流动结构，直观地显示了不同频率流场之间的差别，表明了DMD方法在对复杂大气动力学系统进行模态分解时的优势。通过不同时刻，模态叠加的重构流场与真实流场的直观比较，表明DMD方法只由前面6阶模态就能基本包含原始流场的流动信息，从而实现流场的准确重构。

Analysis of the modes of 200 hPa jet based on Dynamic Mode Decomposition

In this paper,a method of Dynamic Mode Decomposition(DMD) is proposed,so as to analyze the atmospheric motion data,with the aim of improving our understanding of atmospheric motion characteristics.The modal analysis of the 200 hPa jet is performed using the DMD method,andthe main modes,along with theircorresponding frequency and the decay/growth rate of flow,are obtained.Next,a dynamic reduced-order model of the evolution of the 200 hPa jet is established,which is able to reconstruct and predict the dynamic development process of the jet.The study results confirm that the DMD method is able to successfully capture the flow structures of different scales of the 200 hPa jet stream flow.The results also illustrate the differences between the flow with different frequencies,by comparing and analyzing the flow field information contained in the first 6-order main modes,thereby indicating the advantages of the DMD method in modal decomposition of complex atmospheric dynamic systems.The comparisons between the real and reconstructed flow fields by the mode superposition at different times indicate that the first 6-order modes contain the greatest amount of information regarding the original flow fields,from which they can be accurately reconstructed.