Accelerating Transitions and Intensity of Dry-to-Wet Hydroclimate Whiplash Across the Contiguous United States
Abstract
Rapid transitions from dry to wet conditions, often referred to as hydroclimate whiplash, can amplify risks to water security, food production, and human livelihoods. However, it remains unclear whether such transitions are becoming more frequent, faster, or more intense across the contiguous United States (U.S.). Previous studies have primarily used monthly or seasonal drought metrics to detect whiplash, potentially overlooking transitions at sub-monthly timescales. Here, we use a rolling Standardized Precipitation Evapotranspiration Index (SPEI) to identify dry-to-wet whiplash events during 1981–2024 and characterize their climatology and trends in frequency, transition time, and intensity. We also assess the relative roles of precipitation (P) and potential evapotranspiration (PET) in event occurrence. We find no statistically significant nationwide increase in event frequency, although significant increases emerge in the Southwest and Southeast, as well as for rarer, more extreme events. In contrast, transition times have shortened significantly, particularly in the Midwest, Southern Great Plains (SGP), and Southeast. Event intensity has also strengthened in most climate regions. Based on the 30-day SPEI, about 71% of dry-to-wet transitions occur within 30 days, and this proportion has increased over time. P anomalies dominate event occurrence, accounting for about 80% of the transition signal. PET plays a relatively larger role in the western than eastern U.S. and contributes substaintially to increasing event intensity. This study highlights the value of rolling drought indices for capturing rapid hydroclimate shifts and the need to incorporate dry-wet transitions into drought and flood monitoring frameworks.
Tian Yang
Ph.D. student in Environmental Science
