The horizontal and vertical energy exchanges for a composite of seven South Atlantic Convergence Zone (SACZ) episodes were studied by expansion into normal mode functions, with an emphasis on the vertical energy partition between external and internal modes and on the energy interactions within and among various horizontal oscillation modes: Rossby, Kelvin, Mixed Rossby-Gravity and West and East Gravity. A maximum share of the total energy (about 60%) was found in the 4th to 7th internal modes at equivalent highs between 100 and 600 meters, especially over large part of the central South America and near the equator including the SACZ region. As the latitude increases, the energy is distributed towards the lower order modes (n = 1 to 3). For the horizontal energy partition, the most expressive contributions were obtained for the self-interactions of the Rossby and Kelvin modes and for Rossby-Kelvin cross interactions in all vertical mode categories. The Rossby-Kelvin cross interactions constituted the main process for constructive energy interferences in the SACZ region. The vertical mode interactions indicated that the percentage of total energy increases from low levels to the stratosphere with maximum positive (negative) interferences in high levels (stratosphere), for the 4th to 7th internal modes.
Energetics; normal mode functions; South Atlantic Convergence Zone (SACZ)
