부산대학교 도서관

Droughts are associated with large‐scale modes of variability, synoptic‐scale systems, and terrestrial processes. Quantifying their relative roles in influencing drought guides process understanding, helps identify weaknesses in climate models, and focuses model improvements. Using a Lagrangian back‐trajectory approach we provide the first quantification of the change in moisture supply during major droughts in southeast Australia, including the causes of the changes. Drought onset and intensification were driven by reduced moisture supply from the ocean, as moisture was circulated away from the region, combined with an absence of precipitation‐generating mechanisms over land. During termination, strengthened moist easterly flows from the Tasman and Coral Seas promoted anomalously high rainfall. Our approach reveals terrestrial moisture sources played a secondary role, amplifying rainfall anomalies by less than 6%. Simulating droughts therefore requires deeper understanding of the relationship between moisture advection and synoptic‐scale circulation and how large‐scale climate variability and terrestrial processes modify these relationships. Plain Language Summary: The relative roles of atmospheric circulation, weather systems, and land surface processes in recurring droughts in southeast Australia are unclear. We tracked the path of moisture as it moved through the air to find where the rain in southeast Australia comes from and what was different in the atmosphere and land surface during the development, deepening and breaking of three major droughts. We found that the leading cause for drought was that moisture originating from the oceans did not reach the Murray‐Darling Basin as often and produced less rain when it did. The drying landscape exacerbated the low rainfall conditions but had a smaller effect than the ocean. The droughts were broken by strong systems from the east carrying moisture from the ocean into the region. To better model and predict drought we therefore need to understand the relationship between ocean moisture and the weather systems that transport it to the land and how the relationship is affected by the land surface and variability within the climate. Key Points: Southeast Australian droughts are driven by circulation anomalies that reduce moisture inflow and a lack of precipitation‐generating mechanismsMoisture for drought termination is typically sourced from the Tasman and Coral SeasLand surface moisture sources amplify drought by up to 6%, minor compared to ocean influence [ABSTRACT FROM AUTHOR]