Global droughts connected by linkages between drought hubs

Quantifying the spatial and interconnected structure of regional to continental scale droughts is one of the unsolved global hydrology problems, which is important for understanding the looming risk of mega-scale droughts and the resulting water and food scarcity and their cascading impact on the worldwide economy. Using a Complex Network analysis, this study explores the topological characteristics of global drought events based on the self-calibrated Palmer Drought Severity Index. Event Synchronization is used to measure the strength of association between the onset of droughts at different spatial locations within the time lag of 1-3 months. The network coefficients derived from the synchronization network indicate a highly heterogeneous connectivity structure underlying global drought events. Drought hotspot regions such as Southern Europe, Northeast Brazil, Australia, and Northwest USA behave as drought hubs that synchronize regionally and with other hubs at inter-continental or even inter-hemispheric scale. This observed affinity among drought hubs is equivalent to the 'rich-club phenomenon' in Network Theory, where 'rich' nodes (here, drought hubs) are tightly interconnected to form a club, implicating the possibility of simultaneous large-scale droughts over multiple continents. This study shows prominent synchronous co-evolution of drought events in drought hubs in sub-tropical regions, influenced by sea surface temperature patterns and teleconnections. Such simultaneous occurrence of droughts may have detrimental impacts.

Automated summary

This study utilizes Complex Network analysis to investigate the topological characteristics of global drought events, revealing a highly heterogeneous connectivity structure among drought hotspot regions. The co-occurrence of droughts in multiple continents suggests the possibility of simultaneous large-scale droughts.