Time Spectral Analysis of Mid-Latitude Disturbances

Abstract

The method of time series analysis is used to study rawinsonde data in middle latitudes. The spectra reveal baroclinically unstable traveling waves with a preferred period of four to five days and a large amount of variance at lower frequencies. The preferred period of the longer-period waves is roughly 30 days, although the character of the disturbances in this range is highly variable. For the waves of periods between three and seven days, phase relations are derived for the northward component of the wind, the temperature, and the height of constant pressure surfaces. The phase relations are characteristic of traveling baroclinic waves and possess reasonable statistical significance. No stable phases were obtained for the eastward component of the wind or for the longer-period oscillations.