A Spectral Analysis of Wave Activities and Blocking in the Northern Hemisphere Winter

A systematic analysis of wave activities and blocking in the Northern Hemisphere winter is performed with the daily 500mb height fields for the1956-1991 period and the monthly sea surface temperatures (SSTs) for the1970-1991 period. The power spectra in the wavenumber-frequency domain are partitioned into westward propagating, eastward propagating and standing variances. Regional indices are used to classify the seasonal circulation into four categories of circulation patterns according to the dominant blocking activities of the season: Pacific blocking, Atlantic blocking, double blocking, and no blocking. The distinctions among categories of blocking are characterized in the standing, westward propagating and eastward propagating variances. The distinctions are also reflected in the kinetic energy and nonlinear wave-wave interactions of the planetary-scale and the synoptic-scale waves. A composite study of dominant circulation patterns is also presented in this study. The results show that the wave-wave interaction of the planetary-scale and the synoptic-scale waves plays a crucial role in the formation and maintenance of Pacific blocking, and that Atlantic blocking and double blocking might be forced and maintained by baroclinic processes.

並列關鍵字

Blocking ； Wave activity ； Spectral analysis

國際替代計量

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