8 Entropy Production of Atmospheric Heat Transport

Abstract. We examine the rate of entropy produced by the atmospheric general circulation and the hypothesis that it adjusts itself towards a macroscopic state of maximum entropy production. First, we briefly review thermodynamics of a zonally-averaged, dry atmos-phere. We examine the entropy balance of a dry atmosphere, and identify the key processes that lead to entropy production. Frictional dissipation and diabatic eddy transfer are the major sources of entropy production, and both processes are dominated by baroclinic eddies in the middle latitudes. Secondly, we derive a simple solution for the upper bound of en-tropy production from the energy balance constraint, which can be compared to the simu-lated temperature distribution simulated by an idealized GCM. These temperatures agree well with the MEP solution in the mid-latitude troposphere. However, there are significant differences in tropics where the Hadley circulation controls the large-scale temperature dis-tribution. Finally, we show that the simulated entropy production is sensitive to model resolution and the intensity of boundary layer friction, and explore the significance of dy-namical constraints. We close with a discussion of the implications of the MEP state for global climatology