Stormy Subtropics and Stratiform South: Radar-Based Classification and Analysis of Australian Rainfall Events

Abstract

Australia has a large operational weather radar network spanning multiple climatic regimes. However, data from this network is not commonly used to obtain heavy rainfall event characteristics. Drawing on the methodology presented in Bowden et al. (2024, https://doi.org/10.1029/2023jd039253), areal radar variables are used to identify and characterize rainfall events at 15 Australian radar sites over an 11-year period. Rainfall events over all sites are grouped into three clusters based on their characteristics—stratiform (low rainfall intensities and small contributions from convective areas), convective (localized with high rainfall intensities and strong contributions from convective areas), and persistent (long-lasting, moderately intense, extensive events). Further, the top 100 events by accumulation and intensity were identified for each site. Stratiform cluster events are most common in the cool season, convective cluster events are most common in the warm season, and persistent cluster events exhibit strong regional variation in seasonal occurrence over Australia. Convective cluster events are most common at tropical and subtropical sites, and stratiform cluster events are most common at mid-latitude sites. Persistent cluster rainfall events occur least frequently, but make significant contributions to rainfall totals around Australia. Furthermore, almost all high accumulation rainfall events belong to the persistent cluster, and most high intensity events belong to the convective cluster. Examination of rainfall event environments with reanalysis data shows that persistent cluster events and high accumulation events both occur in environments with strong positive column moisture anomalies and mid-level ascent, consistent with past findings on Australian heavy rainfall environments.