Barotropic spectral modeling of non-linear interaction For transient waves in tropical easterly jet

Abstract

The wave-zonal flow and wave-wave interactions are studied over the sphere for the initial single linear barotropic unstable mode of the mean monsoon tropical easterly jet at 100 mb. The non-divergent barotropic global spectral model with truncation N=20 and M=40 is integrated for 120 days for the study. It is found that the wave-zonal flow interaction leads to an oscillation with a period of 35 days in the wave kinetic energy and enstrophy. The relation between the zonal angular momentum transport and growth-decay cycle of the wave is explored. The wave-wave interaction is responsible for the variation in the period of low frequency oscillation between 25&35 days. The mean kinetic energy and enstrophy spectra, and wave-wave interaction in the wave number domain are computed and their role in the non-linear evolution of the waves is discussed.