Future Changes of Atmospheric Energy Cycle in CMIP5 Climate Models

Future changes in the atmospheric energy cycle were estimated by using 12 climate models from the fifth phase of the Coupled Model Intercomparison Project (CMIP5) and mass-weighted isentropic zonal-mean framework. In this framework, the zonal-mean available potential energy (A(Z)) is converted to the zonal-mean kinetic energy (K-Z) through mean-meridional direct circulations, and K-Z is converted to the wave energy (W), the sum of eddy available potential energy and eddy kinetic energy, through wave-mean flow interactions. The comparison between the late 21st century in a high emission scenario and the late 20th century in the historical scenario indicates a significant increase in A(Z) and K-Z in winter in the Northern Hemisphere (NH) and the Southern Hemisphere (SH). The wave energy significantly decreases in the NH winter but slightly increases in the SH winter. In the NH winter, the stationary wave energy significantly decreases, and the transient wave energy shifts poleward. Global warming reduces the baroclinic instability wave activity, which suppresses the upward Eliassen-Palm flux and wave-induced extratropical direct circulation. It decreases the dynamic energy conversion rates C(A(Z), K-Z) and C(K-Z, W). On the other hand, the diabatic wave energy generation rate (Q(E)) is projected to increase, particularly in the SH. The future W change is consistent with the change in the sum of C(K-Z, W) and Q(E). Changes in both the dynamical energy conversion associated with wave-mean flow interactions and the generation of eddy available potential energy associated with diabatic heating processes are necessary to explain the wave energy change.