Propagation From Meteorological to Hydrological Drought: Characteristics and Influencing Factors

Meteorological droughts can reverberate through the water cycle, impacting water resources, ecosystems, agriculture, and socio-economic sectors. Despite this, there remains a scarcity of studies delving into the transition from meteorological to hydrological droughts and the influencing factors operating at the event level. Using long-term observations spanning nominally from 1979 to 2017, we identified and matched meteorological and hydrological droughts based on standardized drought indices across 1089 catchments globally, and examined the characteristics of drought propagation and their determinants at both catchment and event scales. Our analysis reveals that, at the catchment scale, drought severity weakens in approximately 65% of catchments, while intensity experiences a decline in 96% of catchments during the propagation. Moreover, we find that the propagation ratio of severity (or intensity) is significantly and negatively correlated with the severity (or intensity) of meteorological droughts. This implies that major drought events tend to undergo more substantial attenuation in severity (or intensity) during propagation compared to minor droughts. This finding is also obtained at the event scale. Moreover, we find that the event-scale drought propagation ratio (for both severity and intensity) tends to be higher (indicating less attenuation) in catchments characterized by larger seasonal precipitation variation, higher snowfall fraction, steeper slopes, or larger soil water holding capacity. Conversely, it is lower (indicating more dampening) in catchments with dense vegetation cover. These findings offer crucial insights into drought propagation dynamics across catchments globally, thereby informing the development of more effective drought monitoring and management strategies.