Abstract: In this paper, day-to-day zonal mean kinetic energy, eddy kinetic energy and their interactive conversion, and zonal wavenumbers are computed, using wind field data for 30°S-30°N from 1980-1988. The paper also discusses the evolution characteristics of the kinetic energy at midtroposphere for the tropics of both southern and northern hemispheres and the rules governing seasonal adjustments of the kinetic energy. The difference in Kinetic energy between the tropics and middle-and-higher latitudes is pointed out.