On the time variation in the tropical energetics of large-scale motions during the FGGE summer

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Abstract
A pronounced quasi-periodic variation with a period of 11/2 months (OHM) was observed in the tropical (10°S-20°N) energetics during the FGGE summer using the data generated by the FGGE III-b analyses of the European Center for Medium-Range Weather Forecasts. This quasi-periodic variation in the tropical energetics was found to be mainly attributed to wave 1. The time evolution in the three-dimensional structure and dynamical transport processes of this wave are used to explore how this OHM variation occurred and was maintained. It was revealed that the OHM variation in the eddy-available potential energy essentially occurs north of the equator and in the eddy kinetic energy appears both north and south of the equator. The former variation is possibly supported by the generation of the eddy available potential energy and the latter variation north of the equator is maintained by the release of the eddy-available potential energy due to the thermally direct overturnings. The OHM variation in the eddy kinetic energy south of the equator is sustained by the barotropic interaction between the zonal flow and wave 1. A possible mechanism to induce the OHM variation in the tropical energetics is also discussed. DOI: 10.1111/j.1600-0870.1985.tb00426.x