Hydroclimate Whiplash

Fri, 24 Jul 2026 00:00:00 +0000

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. 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.

Extreme Precipitation

Fri, 03 Sep 2021 00:49:29 +0000

Extreme precipitation events damage infrastructure and property; thus, predicting future precipitation patterns in the context of climate change is important. In this study, precipitation projections from 36 downscaled General Circulation Models (GCMs) under two Representative Concentration Pathway (RCP) scenarios (RCP2.6 and RCP8.5) enabled examination of projected changes in future precipitation for the Clear Creek watershed in Houston, Texas, USA. Precipitation from 1950 to 2099 simulated with GCM were downscaled using the Bias-Correction Spatial Disaggregation method. Ten precipitation indices that represent precipitation amount, precipitation intensity, precipitation duration, and precipitation frequency evaluated how precipitation patterns will likely change. Results show that, at the annual scale, mean precipitation will significantly decrease based on RCP8.5, or remain relatively constant based on RCP2.6. Precipitation intensity and precipitation variability, however, will likely increase. Dry periods will lengthen significantly, whereas the length of wet spells will generally remain unchanged. At the monthly scale, the amount of precipitation, precipitation intensity, precipitation frequency and the length of wet spells will likely increase in September. In contrast, precipitation will likely decrease and dry spells will lengthen in April, May, August, November, and December. This finding illustrates that the intra-annual variability in precipitation will increase. The projected changes in precipitation under RCP8.5 are generally greater compared with RCP2.6. Differences between the scenarios are more pronounced towards the end of the century. Houston has recently experienced substantial precipitation variability, including severe drought and record-breaking precipitation from Hurricane Harvey in 2017. These events are consistent with the long-term GCM projections. Findings from this study can be applied to help manage water resources and enhance adaptability to climate change.

extremes | Hydroclimatology Group @O'NeillIU

Hydroclimate Whiplash

Extreme Precipitation