A theoretical study of the annual variation of atmospheric energy

Abstract

The zonally averaged equation for a two-level, quasi-geostrophic model are used to calculate the annual mean values and the first harmonic of the annual variation of the midtropospheric temperature and the zonal winds at the upper and lower levels. The diabatic heating in the model is of a simple Newtonian form. The effects of surface skin friction and of internal friction are included together with a simple parameterization of the meridional eddy transport of sensible heat, while the transport of zonal relative momentum by the eddies is neglected, thereby restricting the motion to the largest meridional scale. From the solution of the equations it is possible to calculate the annual mean values and the first harmonic of the annual variation of the amounts of zonal available potential energy and zonal kinetic energy and, also, the generation of zonal available potential energy, the convertions from this form of energy to eddy available potential energy and to zonal kinetic energy, and the dissipation of zonal kinetic energy by friction. The results show that the simplified model is capable of reproducing several important aspects of the annual variation of atmospheric energetics. The phase relationships involving the time lag between the generation of zonal available potential energy and the dissipation of kinetic energy as well as the time lag between the seasonal forcing and the maxima of zonal available potential energy and zonal kinetic energy are well reproduced. There are differences between the theoretical results and observational studies with respect to the intensity of the general circulation and the amounts of energy. The sensitivity of the theoretical solution to the numerical values of the physical parameters is investigated. DOI: 10.1111/j.2153-3490.1970.tb01931.x