Spectrum Analysis of Wave Disturbances over Northern Taiwan in Winter

Shun-Der Ko

Abstract

　　Spectrum analysis is made for zonal-and meridional-component of upper winds from 700-mb to 150-mb levels at Taoyuan (N 25˚03′, E 121˚13′) during the period December 1965 through February 1996. Two different high-pass filters are used respectively prior to the spectrum analysis.
　　Power spectra of the wind components reveal two distinct types of disturbances. One is the wave with period of 8-10 days throughout the troposphere, the other 3-4 days in the lower and upper troposphere.
　　The horizontal and vertical structures of the disturbances are studied by computing the cross spectrum, the coherence and the phase difference the zonal and meridional wind disturbances. In the troposphere, the phase of the disturbances at upper level lags behind that at lower level. The axis of disturbance at each level is directed generally from southwest to northeast.