The Energy Exchange between the Baroclinic and Barotropic Components of Atmospheric Flow in the Tropics during the FGGE Summer

Abstract

The wind fields in the tropics (15°S?15°N) generated by the FGGE IIIb analyses of the European Center for Medium-Range Weather Forecasts are used to compute the kinetic energy of baroclinic (vertical shear) and barotropic (vertical mean) flows, and the conversion between these two energy reservoirs for the FGGE (1979) summer. The computations are carried out in the longitudinal spectral domain. The computational results show that the baroclinic kinetic energy of every wave component is larger than its corresponding barotropic kinetic energy. The kinetic energy is converted from the baroclinic flow to the barotropic flow, and in the tropics the magnitude of this energy conversion is an order smaller than that in middle latitudes as studies by Wiin-Nielsen and his colleague have shown. This energy conversion is dominated by wavenumber 1, like other spectral energy studies of the tropical upper troposphere. Since the computations of the conversion between baroclinic and barotropic kinetic energy only involves the horizontal wind fields, the analysis of this energy conversion may offer an alternative in exploring the atmospheric energetics in the tropics. Further effort is made to compare the contributions of the standing (time-mean) and transient (departure from the time-mean) modes to the aforementioned energy variables.