MJO特征的多尺度子空间重构
投稿时间: 2015-06-16  最后修改时间: 2015-10-22  点此下载全文
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梁湘三 南京信息工程大学 sanliang@courant.nyu.edu 
中文摘要:通过构造两种不同类型的理想序列,将多尺度子空间变换(MWT)与传统使用最多的带通滤波方法(Butterworth)进行比较发现:MWT滤波出的结果在整体上与原序列几乎完全吻合,而Butterworth的滤波结果在振幅上总是偏小;另一方面MWT对边界的处理也比Butterworth要好。为此使用两种方法分别对MJO进行重构,并比较两种方法下MJO特性的差异。结果表明:在纬向(zonal)传播上,两种方法得出的MJO基本类似;但在经向(meridional)传播及其季节变化上,两种方法的结果无论在强度还是分布上都存在明显的差异。本文发现:MJO波列从年初到夏季由南向北传播,而从夏季到岁末传播方向却发生逆转,变成由北向南,这一点与前人的结果很不相同。
中文关键词:热带大气季节内振荡(MJO),多尺度子空间变换(MWT),Butterworth滤波
 
Reconstructing the MJO with multiscale window transform
Abstract:Recently Liang and Anderson developed a new functional analysis tool, i.e., the multiscale window transform (MWT) to faithfully represent and decompose the complex nonlinear multiscale processes within the atmospheric and oceanic circulations. In this study, two types of idealized series are constructed to test the effect of the MWT versus the traditional and mostly used band-pass Butterworth filter. It is found that the MWT always makes fairly accurate reconstructions, while the Butterworth filter tends to yield series with smaller amplitude. Besides, the boundary effect is successfully suppressed in the MWT reconstructions, in contrast to the Butterworth results. With these observations in mind, we reconstruct the MJO using these two methods. The results show no much difference in the zonal propagation pattern. But on the meridional distribution, both the strength and propagation pattern are quite different. This is especially significant on the yearly mean distribution. It is found that, from January through June, the MJO wave packet propagates from south to north; but from June through December, the propagation reverses its direction, becoming from north to south. This propagation reversion is quite different from the scenarios revealed in previous studies.
keywords:Madden and Julian Oscillation(MJO),Multiscale Window Transform (MWT), Butterworth filter
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