Empirical Orthogonal Representation of Time Series in the Frequency Domain. Part II: Application to the Study of Tropical Wave Disturbances

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Abstract
Rawinsonde data from the western Pacific region for the summer of 1967 are expanded in terms of complex empirical orthogonal functions and the results are compared with those of previous investigations based on the same data set. The results and conclusions are consistent with those based on spectrum analysis and compositing, except in a few cases where it has been possible to resolve ambiguities in the earlier work. The new method has been particularly helpful in clarifying the relationship between the mixed Rossby-gravity waves of the upper troposphere and the synoptic-scale, westward propagating waves of the lower troposphere. The new results indicate that these two disturbance types are so strongly coupled that it is not possible to separate them.