Spectral Energetics of the General Circulation and Time Spectra of Transient Waves during the FGGE Year

Abstract

The spectral energetics of the general circulation are presented for the entire FGGE year based on the GFDL analyses of FGGE observations. The global energy balance and those of the Northern and Southern hemispheres show a reasonable agreement. However, examining the energy flow in the wavenumber domain reveals a marked contrast between the two hemispheres in both energy and energy transformations. The annual variations of energy variables are large, and there are also pronounced differences of seasonal characteristics between the hemispheres. With the one-year time series of energy variables, time spectra of transient waves are examined at 500 and 100 mb in order to evaluate their contribution to the time-averaged kinetic energy and baroclinic conversion. Characteristic distributions of power spectra for kinetic energy and available potential energy are described for the Northern and Southern hemispheres. In cyclone-scale disturbance almost the entire baroclinc conversion is supported by transient waves. There are pronounced contrasts between the Northern and Southern hemispheres in the conversion cospectra at various zonal wavenumbers.