Australian Summer Monsoon Bursts: A Moist Static Energy Budget Perspective

The Australian monsoon's wet season is associated with sequences of wet and dry conditions known as bursts and breaks, which usually have timescales of a week or two. There are several hypotheses for the physical processes involved in monsoon bursts, ranging from the effects of the Madden-Julian Oscillation to extratropical influences. We analyze rainfall bursts in Northern Australia using a moist static energy (MSE) budget framework. We separate the bursts into three types and further separate them into pre-monsoon, active monsoon, and post-monsoon. We then apply ERA5 data to calculate the MSE budget for each burst and construct composite bursts for each of the three types. We find that the horizontal advection of MSE over the tropical northern Australian convergence zone is the most critical term in the budget for the day-to-day precipitation variation. MSE-related gross moist stability analysis reveals that each type has distinct characteristics. The burst type associated with active monsoon bursts displays convective growth and decay patterns both before and after the precipitation peak, which is typical of oceanic convection. A low-rainfall burst type, which is often seen before monsoon onset, is linked to coastal convection and has minimal rainfall decay after the burst. Finally, a sustained high-rainfall burst type, mostly observed at the end or after the monsoon retreat, has growth characteristics similar to the typical monsoon burst but does not decay, maintaining very high rainfall for at least a week due to a rearrangement of the circulation and local thermodynamic structure of the atmosphere. The Australian Summer Monsoon (ASM) is associated with sequences of wet and dry conditions known as bursts and breaks during the extended summer months (October-April). Although understanding of these phenomena has progressed, there are still gaps in both our knowledge of the processes that produce bursts and our ability to predict their evolution. Energy budgets are evaluated in this study to gain insight into the key mechanisms involved in burst evolution. It is found that energy export/import via large-scale circulation is critical in determining the evolution of monsoon bursts. Furthermore, the research identifies various types of bursts, each with its own set of key mechanisms. These findings provide important insights into the dynamics of the ASM bursts and may help improve predictions of future bursts and breaks, allowing for better management of the region's agricultural and ecological systems. Australian monsoon burst moist static energy budget analysis reveals several distinct burst typesOnly one of the burst types follows the archetypal gross moist stability cycle of oceanic convectionHorizontal moisture advection is critical for the burst evolution, but the details vary between types