A Multiscale Evaluation of the Wet 2022 in Eastern Australia

Eastern Australia experienced record-breaking rainfall and flooding during 2022, which devastated communities and led to over AU$6 billion of damage. In this study, we conduct a multiscale analysis to understand why 2022 was unusually wet with multiple record-breaking rainfall events over the year. We assess the synoptic- and mesoscale conditions during three key periods: February-March, July, and October. These periods were chosen because they were impactful and represent three different seasons. Next, we examine the large-scale climate drivers and evaluate how unusual these events were compared to previous years. Finally, we discuss predictability and the possible impact of climate change on the drivers of heavy rainfall in eastern Australia. The exceptional rainfall was likely due to excessive slow-moving cyclones combined with ample atmospheric moisture flux. The key climate drivers (El Niño-Southern Oscillation, Indian Ocean dipole, and Southern Annular Mode) primed the synoptic conditions for frequent rain-bearing weather systems. There was limited predictability beyond the 1-week lead time for the February-March and July events, but the 1-month seasonal forecast for October indicated rainfall in eastern Australia. The complexity of multiday extreme rainfall makes it difficult to distinguish the role of climate change from natural variability. However, we highlight where future research could focus to help us understand climate risks to this region. Our results emphasize the importance of examining rainfall from multiple perspectives and considering the interactions between weather and climate scales because analyzing drivers in isolation is insufficient for explaining high-impact weather.