Abstract
A power spectral analysis is made for the data of upper winds at Canton Island (S 02°46", W 171°43') from June 1957 to May 1960. For the whole data of three years, the power spectrum of the meridional wind component gives a peak at a period of about four days. To examine the relation between the disturbances with this period and the mean flow which exhibits quasi-biennial periodicity, the mean flow and the power spectra of the disturbances with periods less than ten days are computed for every 60-day time series data.
For the meridional wind component, the time sequence of the power spectra shows that disturbances with a period of about four days are prevailing in the lower stratosphere during almost all the time. The regions of relatively strong power spectral density in this period range descend with time as the alternation of the mean flow does. It is shown that these regions are observed where the mean flow weakens with height.
The vertical extent of the disturbances is roughly 4km on the average. The phase of the disturbances at lower levels lags behind that at upper levels. The phase lines of the disturbances tilt westward with height, in consideration of their westward propagation supported by additional synoptic analyses.
