ON TRANSFORMATION OF KINETIC ENERGY BETWEEN THE VERTICAL SHEAR FLOW AND THE VERTICAL MEAN FLOW IN THE ATMOSPHERE

Abstract

The kinetic energy of the horizontal, hydrostatic flow is divided into the kinetic energies of the vertically integrated flow and the deviation from this flow, the so-called shear flow. The energy transformation between the two types of flow is found in the general case of the primitive equations and also for the most simple quasi-non-divergent model. The two transformations are discussed, and the energy transformation in the quasi-non-divergent model in the two-parameter case is discussed as a function of wave number using linear theory. The energy conversion has been computed on a daily basis for the month of January 1959, and compared with earlier results of computations of transformations between available potential energy and shear flow kinetic energy. It is shown that the latter conversion changes the kinetic energy of the shear flow and not that of the mean flow. The residence time is estimated for the shear flow as well as the mean flow. The energy transformation between the vertical shear flow and mean flow due to the non-divergent and divergent flow has been computed in the wave-number regime for the first 10 zonal wave numbers for each day in January 1959. It is found that the energy conversion between shear flow and mean flow is about 30 percent of the conversion between the available potential energy and the shear flow kinetic energy. A further result is that the energy conversion between the shear flow and the mean flow due to the divergent part of the flow is estimated to be negative and ahout 10 percent of the conversion due to the non-divergent part of the flow. The energy conversion as a function of wave number shows a maximum for the most unstable baroclinic waves.