投稿时间:2015-06-16  修订日期: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 
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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