时-空二维波传播分解方法及其在季节内振荡分析中的应用

The space-time wave propagating decomposition and its application to analysis of intraseasonal oscillation

中文关键词:  时-空二维波传播分解， 大气季节内振荡， 联合经验正交函数分析

英文关键词:Space-time wave propagating decomposition (STWPD), Intraseasonal oscillation (ISO), Combined empirical orthogonal function (CEOF)

中文摘要:

      大气季节内振荡最显著的特征之一就是其复杂多变的传播特征。为了进一步分析大气季节内振荡的传播特征及其不同传播方向分量的不同作用，基于波的传播理论，对时 空谱分析进行了发展，提出了时 空二维波传播分解方法，并用理想函数验证了其正确性和可行性。结果表明：对任一时 空二维序列，采用此方法均可正确地分解得到空间上具有不同传播方向的3部分分量：前进波、后退波和驻波分量。之后，对向外长波辐射（OLR）、200和850 hPa纬向风的东传、西传分量以及驻波分量分别进行联合经验正交函数（CEOF）分析。结果表明，在东传分量上，热带大气季节内振荡主要表现为纬向1波的向东传播，与对流层高、低层纬向风呈现反位相的斜压结构，和未分解的情况相比，前两个主要模态重要性的排序出现了颠倒，说明通过时 空二维波传播分解，避开了各分量之间的相互影响，进一步揭示了前两个模态的物理意义及其在季节内振荡中的重要性；在西传分量上，热带大气季节内振荡主要表现为纬向2—3波的向西传播；驻波分量主要表现出印度洋和太平洋的反位相结构。对热带地区大气季节内振荡的东、西分量的分析，深化了对热带大气季节内振荡东传、西传特征的了解，这对于热带大气季节内振荡更加准确预报及其物理模型的建立有着重要的意义。时 空二维波传播分解方法改变了原有分析方法仅对各变量进行整体分析的思路，为进一步了解大气季节内振荡现象提供了一个新的视角和工具。

英文摘要:

      One of the most prominent features of the intraseasonal oscillation (ISO) is its complicated propagation. To investigate the characteristics of the ISO propagation and the influences of different propagating components of the ISO, we here propose a further developed space-time spectral analysis method, the space time wave propagating decomposition (STWPD) based on the wave theory. The analyses using both ideal functions and reanalysis data confirm the validity and practicability of the STWPD. The result shows that any space time series can be decomposed into three components with different propagating directions: the progressive, retrogressive and standing waves, respectively. It is shown from the combined empirical orthogonal function (CEOF) analyses of the eastward, westward and standing components of the outgoing longwave radiation (OLR) and the zonal winds at 850 hPa and 200 hPa that: (1) the eastward component of the ISO exhibits the eastward propagation of the zonal wave number 1 and, the zonal winds at the upper and lower troposphere have a baroclinic structure and are out of phase; (2) the westward component of the ISO displays the westward propagation of the wave numbers 2-3; and (3) the standing component shows a feature of antiphase in the Indian Ocean to the Pacific Ocean. The analyses of the different components of the tropical ISO in this study may deepen our understanding of the ISO propagation and have significant meanings for constructing the physical model of the ISO and predicting it. Different from the previous methods, the STWPD provides us with a new tool and visual angle to investigate the ISO by analyzing its different propagation components. 