Kinetic energy conversions by horizontal and vertical eddy processes from 5 years of hemispheric data

Certain zonally averaged quantities related to the kinetic energy balance of the earth's atmosphere are investigated. Horizontal and vertical transport and generation terms are evaluated from observational data from about 800 sounding stations over the northern hemisphere spanning a 5-year time period. Several objective analysis schemes have been studied for their effect on the results. General agreement among the derived values was found. Using the analysis scheme considered best for long-term and seasonal time periods, it is shown that both horizontal and vertical eddy stresses play important roles in maintaining the kinetic energy of the mean zonal flow. A significant result is that over the long term the generation of kinetic energy by countergradient vertical eddy processes nearly balances the destruction of kinetic energy associated with positive viscous effects in the vertical. During certain periods of the year, however, significant departures from this near balance may occur. In spring, countergradient fluxes predominate, whereas in fall positive viscous processes are the larger.