Drought Cascade in the Terrestrial Water Cycle: Evidence From Remote Sensing. Issue 14 (21st July 2021)

• Record Type: Journal Article
• Authors: Farahmand, Alireza; Reager, J. T.; Madani, Nima
• Is Part Of: Geophysical research letters. Volume 48:Issue 14(2021)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2021-07-21
• Subjects: cascading effect -- CONUS -- drought -- remote sensing; Geophysics -- Periodicals; Planets -- Periodicals; Lunar geology -- Periodicals; 550
• DOI: 10.1029/2021GL093482
• Languages: English
• ISSNs: 0094-8276

Abstract

Abstract: Droughts are complex phenomena that typically evolve slowly over time. They originate through interactions between the atmosphere and the land surface, but show delayed evolution as they cascade through soil moisture, surface, and groundwater supplies, sometimes resulting in prolonged and insidious impacts on regional hydrological systems. While previous studies have observed this cascade phenomenon at select in situ locations, the temporal characteristics of drought cascades have never been quantitatively estimated at large scales using primarily remote sensing techniques. Here, we use satellite observations of vapor pressure deficit, Precipitation, and terrestrial water storage, and reanalysis‐based estimates of column soil moisture to characterize cascade phenomena for four major US drought case studies. By mapping the time evolution through this suite of variables, we observe large‐scale behavior generally consistent with theory and are able to quantify emergent patterns in the evolution of drought signals that may support improved future predictability. Plain Language Summary: Droughts are slow‐building disasters that result in billions of dollars of losses every year. A better understanding of how long droughts take to propagate and persist depends on the ability to observe drying beneath the land surface, where drought effects reach deep to disturb soil moisture and groundwater stores that remain hidden to the naked eye. In this study, we used state‐of‐the‐art satellite observations to measure not only the surficial causes of drought, but also to characterize the beginning, ending, and severity of drought at depth in the soil column and in groundwater. For four major historical droughts in the United States, we find similar patterns in the timing of the drought cascade through the land surface that may be useful to tracking drought evolution more comprehensively in the future. Key Points: This study presents the first multievent analysis of drought cascades using satellite vapor pressure deficit (VPD), precipitation, terrestrial water storage (TWS), and reanalysis soil moisture We find characteristic lag times in the propagation of drought onset, termination, and timing from precipitation to soil moisture and TWS On average, it took 2.5 months for precipitation deficits at drought onset to propagate to soil moisture, and 8 months to propagate to TWS