Dynamic development of global contiguous flash droughts: from an event-based spatiotemporal perspective

Flash droughts can induce serious adverse effects on local ecology due to their rapid intensification. However, individual flash drought events have not been thoroughly analyzed to demonstrate their dynamic evolution and changes. Here we use a 3-D connectivity algorithm to identify large contiguous flash drought events globally from an event-based perspective, which allows for effective tracking of their full spatiotemporal development. Results show that during 1980–2020, 2322 large contiguous flash drought events occurred and mainly distributed globally in nine hotspots, with a strong seasonal preference for warm seasons. Flash drought events of longer lifetime and travel distance are more likely to occur at the high-latitudes. The intensity, duration, and frequency of these events increase statistically significantly, while their affected area and translation speed decrease. Although regional variations in propagation patterns exist, flash drought events tend to propagate more toward the northeast. Across much of the globe, the preceding meteorological conditions in over 50% of flash droughts are marked by the concurrence of elevated regional temperatures and precipitation deficits. The dominant role of individual drivers exhibits notable spatial heterogeneity, largely influenced by the latitude and regional weather systems. Precipitation deficits tend to be the primary driver in monsoon-affected regions, while elevated temperatures predominantly govern flash drought onset in the high-latitudes of the Eurasian continent. Precipitation deficits primarily (38.9%) determine the intensity of flash droughts, while high temperatures play a dominant role (42.2%) in the duration of flash droughts. Our results provide a new perspective for future projection of drought events.