Dependence of the energy budget at mesopause heights on variable circulation patterns

Abstract

The global energy budget of the mesopause region strongly depends on the variable circulation patterns, controlling in particular the heat transport. A better understanding of this dependence is desirable. Regarding the complexity of the problem and the difficulties in obtaining suitable measured data on a global scale numerical models appear to be a convenient and necessary tool to approach the problem. In this paper energy budget studies are presented employing a mechanistic 3-d circulation model of the middle atmosphere (0–150 km). Special attention is drawn to two terms of the mesopause heat budget: the adiabatic heating by vertical motions and diabatic heating by eddy heat fluxes. The model calculations show heating and cooling rates of more than 100 Kelvin per day which can even occur at high latitudinal regions due to the wave — mean flow interaction of stationary and planetary waves. A high variability of the eddy heat fluxes in space and time is found according to temporal and spatial changes of tidal, gravity and planetary wave activity. The major component of mechanical dissipation is contributed by gravity wave drag, which plays an essential role in controling the strength and variability of the circulation patterns at mesopause heights.