Australian Summer Monsoon: Reanalyses Versus Climate Models in Moist Static Energy Budget Evolution

The Australian summer monsoon (ASM) influences the tropical hydro-climate of Northern Australia during the extended summer months (October-April). Despite advances in understanding the ASM, climate models vary widely in their depiction and projections of its future behavior remain uncertain. This study investigates the moist static energy (MSE) budget and examines the gross moist stability (GMS) evolution throughout the monsoon cycle using two reanalysis data sets. We then assess the ability of Atmospheric Modeling Intercomparison Project (AMIP) simulations of climate models to reproduce not only the monsoon seasonal cycle of rainfall but the associated mechanisms revealed by the budget analysis. The budget analysis shows a strong influence of the regions to the north and west of our study area for the import of moisture and export of energy into and away from the ASM. We find that models reproduce this influence qualitatively, but not quantitatively. As in previous studies, we identify two major regimes of the GMS associated with the absence (higher GMS) or presence (lower GMS) of convection. Whilst climate models are able to distinguish the two regimes, they significantly overestimate the GMS in convectively active periods, owing largely to profile of ascent that is too top heavy. Models with more realistic precipitation do not consistently offer more accurate representations of dynamic processes, as evaluated by the MSE budget and GMS. This highlights limitations in assessing models based solely on single variables. To enhance the generalizability of these findings, future studies should employ models without prescribed sea surface temperatures. During the extended summer months (October-April), the Australian Summer Monsoon (ASM) brings rain to Northern Australia, which has a significant impact on local agriculture and ecosystem maintenance. A lot has changed in how we think about the ASM, but still, climate models show a wide range of skills in their ability to simulate the monsoon rainfall and its changes in a warmer climate, making the ASM's future very uncertain. In this study, we evaluate models using moisture and energy budgets to see how they differ in terms of key mechanisms involved in the monsoon evolution. We find that models that are good at reproducing the seasonal evolution of precipitation, but do not always perform better at reproducing overall moisture and energy transport. Analysis of the moist static energy budget provides new insights into the seasonal evolution of the Australian monsoon Most of the climate models studied tend to overestimate the gross moist stability in the active monsoon phase relative to reanalysis Models with more realistic precipitation evolutions do not necessarily have better representations of dynamic processes