The Variability of the Tropical Diurnal Cycle Associated with the Madden-Julian Oscillation

Intraseasonal variability of the atmosphere represents an important timescale that bridges climate and weather. A number of previous studies showed that phenomena that occur on intraseasonal timescale, such as the Madden–Julian Oscillation (MJO), influence global circulation and interact with a wide range of spatial and temporal weather and climate phenomena. While previous studies suggest that the accurate representation of intraseasonal variability in numerical models is important to improve the skill of extended forecasts and projections of climate, we have not achieved a complete understanding of the role of the tropical intraseasonal variability in the energy cycle of the climate system. This study attempts to examine the role of the intraseasonal variability in the climate system through an energetics perspective using reanalysis datasets. The available potential energy and kinetic energy are decomposed into components constructed using three temporal timescales including the intraseasonal, and periods shorter and longer than intraseasonal timescales. The latter two timescales represent the synoptic and slowly-varying background state, respectively. This temporal decomposition allows quantification of the amplitude and direction of energy conversion between the intraseasonal, background, and synoptic timescales and their global distribution. By examining the climatological quantities of the energy conversion and transport, this study provides insights into how much of the tropical intraseasonal energy is generated in-situ, transported meridionally, and exchanged with the energy of climate and weather phenomenon. The results will improve our understanding of the tropical-extratropical interactions of intraseasonal energy and the role of tropical intraseasonal variability in maintaining the tropical and extratropical synoptic variability and climatological mean flows.