When Do Droughts Initiate and Terminate in Australia? (#148)
Recent developments in eastern Australia have once again shed a light on the issue of drought management in Australia. One of the pressing issues is the uncertainty involved in predicting the onset and subsequent termination of drought, information much needed by water managers and the agricultural community to reduce the impacts of drought. Therefore, the aim of this study was to characterise the historical seasonal patterns in drought onset and termination in the major climate zones of Australia. This was achieved using monthly rainfall data for 14 stations from the Bureau of Meteorology’s High-Quality Climate Datasets and the Standard Precipitation Index (SPI) to create a drought history at each site spanning 1900 to 2018. The average run length and severity of drought was then calculated, along with the season in which droughts initiated and terminated. The number of droughts varied between nine and 15, with average drought lengths between seven and 11 months, and average severity between -1.44 and -1.87 (moderate to severe on the SPI scale). Overall the longest droughts were observed at Meredith, Vic, while the most severe at Happy Valley, SA. Seasonal patterns of onset were found to be summer dominated in the north and autumn-winter dominated in the south of the country, aligned with rainfall seasonality and the dominant large-scale climate drivers. Spatial patterns in termination were more variable, however significant insight was gained into seasons more favourable for drought ending rains (synoptic events) at each location. This study expands the scope of drought characterisation work conducted in Australia and presents a novel approach to assessing drought onset risk and termination probability at the continental-scale. In doing so, a platform is developed to better predict drought and improve drought preparedness, which will in turn, result in the impacts of drought being reduced.