LARGE-SCALE BALANCE OF KINETIC ENERGY IN THE ATMOSPHERE

Abstract

The vertical distribution and seasonal variation of the kinetic energy balance of the atmosphere are studied. From 11 months' daily wind and geopotential data during 1962 and 1963 over North America, the generation due to the work done by the horizontal pressure force, the local change, the horizontal outflow, and the vertical transport, are evaluated for 20 pressure layers from the surface to 50 mb. The dissipation is then obtained as the residual to balance the kinetic energy equation. The generation and dissipation are at a maximum in the planetary boundary layer. They decrease gradually to a minimum in the mid-troposphere, increase again to the second maximum in the upper part of the atmosphere, then decrease again farther upward. The generation and dissipation are approximately balanced in the lower troposphere, particularly in the boundary layer, for the large-scale domain of analysis. The generation and dissipation of the kinetic energy are significantly large both in the lower troposphere and in the upper part of the atmosphere. However, in view of the amount of the kinetic energy contained in different portions of the atmosphere, the energy generation and dissipation are most intense in the lower troposphere, especially in the boundary layer. The efficiency of the dissipation in different portions of the atmosphere is also examined in terms of the depletion time. The depletion time is orders of magnitude shorter in the boundary layer than in the mid-troposphere. A seasonal change of the energetics is depicted for the one-year period by means of the pressure-time cross sections.