Abstract:According to the framework of energy cycle proposed by Lorenz in 1967,the atmospheric energy cycle is estimated on a monthly basis in the Northern Hemisphere using the NCEP/NCAR reanalysis daily data for the period of 1958—2011.The annual variations of energy reservoirs,conversions,exchanges across the equator,generations and dissipations have been investigated in the present paper.The results show that the energy cycle of the Northern Hemispheric atmosphere varies on annual time-scale evidently.Reservoirs and conversion rates change in the same phase,with values larger in winter,smaller in summer.In winter,the zonal mean energies and eddy kinetic energy are transported northward from the Southern Hemisphere into the Northern Hemisphere.However,in boreal summer,they are transported southward from the Northern Hemisphere into the Southern Hemisphere,whereas the exchange of eddy available potential energy at the equatorial boundary is in contrast.A maximum in generation of the zonal mean available potential energy takes place in the fall,and the generation of eddy available potential energy has a maximum in the summer.The dissipations of both zonal mean and eddy kinetic energy are stronger in winter but weaker in summer.In the annual mean case,the cross-equatorial fluxes are smaller than the energy conversion processes.In the meridional direction,the zonal mean available potential energy mainly appears in high-latitudes,the zonal mean kinetic energy mainly in mid-and low-latitudes,and the eddy energies mainly in mid-and high-latitudes.Further more,the conversion processes of atmospheric energies are more active in the middle latitude regions.