SPECTRA OF LARGE-SCALE ATMOSPHERIC FLOW AT 300 MILLIBARS

Abstract

Data at 300 mb for January-February and July-August, 1949, are used to compute spectra of atmospheric turbulence as a function of wave number along various latitude circles. Power spectra are computed for the zonal and meridional wind, and cospectra for the meridional transfer of angular momentum, dry enthalpy, and kinetic energy. Total spectra are computed daily, and for each season the mean total spectrum is divided into two parts: the spectrum of the seasonal mean flow, and the mean seasonal spectrum of the perturbations. The general characteristics of the power and cospectra are discussed. It is shown, for example, that the spectrum of the mean seasonal flow dominates at low wave numbers, while the mean spectrum of the perturbations is more important at higher wave numbers. The day-to-day variation of the total spectra is also considered. It is found that for power spectra the specific deviation is quasi-constant at all wave numbers, latitudes, and seasons. A method is presented for refining the variance analysis by separating out the interaction variance between the mean flow and the perturbation field.