From precipitation to impact: Understanding the impacts climate non-stationarity through on pace of drought

Theory suggests that a non-stationary, warming climate will intensify the global hydrologic cycle. Yet theoretical expectations of intensification are often at odds with observational records. Understanding how potential acceleration affects the transition between hydrological extremes remains a critical knowledge gap relevant to the session’s goal to better understand the interplay between hydro-climatic states. We investigate the changing pace of the water cycle through the lens of observed lag times between atmospheric drivers and terrestrial drought.

Focusing on the conterminous United States from 1950 to 2020, we employ a multi-metric framework to quantify changes. We begin by analyzing soil water residence time and Water Cycle Intensity (WCI) using data from ERA5-Land, in situ observations and gaged streamflow records. Here, a decrease in residence time indicates a faster turnover, or "flashiness," which fundamentally alters how extremes propagate through the landscape. To link these physical rates to societal impacts, we subsequently analyze drought propagation—specifically the lag time between meteorological drought (Standardized Precipitation Index) and agricultural drought (Standardized Soil Moisture Index). Preliminary hypotheses suggest that as the water cycle accelerates, the buffer capacity of the land surface diminishes, leading to faster propagation of precipitation deficits into soil moisture and runoff deficits. By quantifying these changing lag times, this research provides a new, observationally-driven assessment of how the ‘rate’ of drought is evolving, seeking to provide useful insights for early warning systems and the management of non-stationary transitions between wet and dry extremes.