Spectral study of wintertime kinetic energy of the northern hemisphere in the troposphere

The regional distribution of kinetic energy has been computed and analyzed in a wave number-frequency domain at 850 mb, 500 mb and 200 mb. The distribution of kinetic energy shows a strong geographic dependence. It is found that medium scale (wave number between 6 and 9) westerly waves with medium frequency (period between 3 days and 9 days) significantly contribute to the 2 distinctive kinetic energy maxima located over the North Pacific and the east coast of North America. Easterly waves with medium and high frequency have no substantial contribution.

An analysis of the effects of non-linear interactions on the regional distribution and characteristics of the kinetic energy of the medium scale westerly waves with medium frequency indicates that the contribution of non-linear interactions corresponding to the longitudinal convergence of the flux of kinetic energy is generally larger than that of the terms involving the meridional convergence of the flux of kinetic energy. The primary non-linear interactions occur at mid-latitudes between 30° N and 50° N. The regions at 200 mb (500 mb) located to the north (south) of the maximum intensity of kinetic energy over the North Pacific are characterized by a negative contribution from non-linear interactions. The analysis reveals that the distribution of maximum intensity of kinetic energy over the North Pacific is positively correlated with the distribution of the non-linear interaction contribution. It indicates that non-linear interactions play an important role in the dynamics of atmospheric waves.