Seasonal variation of kinetic energy in the atmosphere

In an attempt to broaden the observational basis of the seasonal variation of the large‐scale atmospheric circulation, Fourier analysis was applied to time series of important kinetic energy variables which were computed for a 5‐year period over the North American Continent. The variance spectra of the direct Fourier analysis are also presented. The year‐to‐year fluctuation of the seasonal variation of the energy variables is apparent. After filtering out the year‐to‐year irregularity, clear basic features of the seasonal evolution were obtained. The kinetic energy level can be described essentially by the one‐year cycle. However, the energy generation, outflow, and dissipation show an important half‐year cycle in addition to the prominent one‐year cycle.