Cascading propagation of subseasonal droughts across the land-atmosphere system

Droughts are commonly classified into meteorological, agricultural, hydrological, and ecological types, yet how these categories interact dynamically and propagate across space and time at subseasonal scales remains poorly understood. Here we show that subseasonal droughts propagate as directional, cascading processes across the land-atmosphere system. We develop an event-based analytical framework using event coincidence analysis to identify subseasonal drought events as sustained extremes in precipitation-evapotranspiration balance, soil moisture, runoff, and vegetation condition across the contiguous United States from 1982 to 2025, using satellite observations and land data assimilation system simulations. We find robust lead-lag relationships and coherent propagation pathways in which meteorological droughts systematically precede agricultural, hydrological, and ecological droughts across space and time. Event coincidence analysis identifies statistically significant drought sources and sinks and their time-lagged directional dependencies, allowing directional propagation patterns to be traced across drought types and regions. We find consistent cross-type drought transitions in several climate-sensitive regions (for example, SPEI → soil moisture → NDVI in the Southern Plains), with meteorological droughts typically preceding agricultural and ecological impacts by several weeks and with variable amplification along the transition. Linking these propagation pathways to near-surface temperature, wind fields, and 850-hPa geopotential height shows that large-scale atmospheric circulation modulates timing and intensity of cross-type drought cascades. These findings show that subseasonal drought evolution is governed by directional temporal cascades and by coherent spatial propagation pathways across the land-atmosphere system, indicating non-local controls and distinct temporal signatures.