Abstract
Studies are conducted to investigate the amplitude increasing and decreasing mechanism of the zonal mean and large-scale wave motions in the tropical upper troposphere during northern summer. For this purpose, composite averages of individual contributions in the kinetic energy equation in wavenumber domain are calculated for the energy increasing, the energy peak and the energy decreasing stages.
It is found that the growth and decay of the zonal mean motion and waves of wavenumbers 1 and 2 are possibly contributed by the energy conversion process related to thermally direct circulation in the tropics. This process is most enchanced in wavenumber 1. In the seasonal mean, waves of wavenumbers 1 to 4 contribute to the maintenance of the zonal mean motion and to the maintenance of waves of wavenumbers 6 to 15.
In some cases, we observe that waves of wavenumbers 3 to 7 do grow by gaining and decay by losing kinetic energy through wave-wave interactions involving wavenumber 1. However, the growth and decay of waves of wavenumbers 3 to 6 may also respond to processes other than wave-wave and wave-zonal interactions. In addition, processes other than the barotropic interactions contribute to the majority of amplitude oscillations of waves of wavenumbers 7 and 8.
