Guan et al. (2025) Anthropogenic enhancement of subsurface soil moisture droughts

Identification

• Journal: Nature Climate Change
• Year: 2025
• Date: 2025-11-14
• Authors: Yansong Guan, Xihui Gu, Aiguo Dai, Tianjun Zhou, Xing Yuan, Ashok K. Mishra, Jakob Zscheischler, Yadu Pokhrel, Lunche Wang, Jianfeng Li, Shengzhi Huang, Sijia Luo, Liangwei Li, Dongdong Kong, Xiang Zhang
• DOI: 10.1038/s41558-025-02458-z

Research Groups

• State Key Laboratory of Geomicrobiology and Environmental Changes, School of Geography and Information Engineering, China University of Geosciences, Wuhan, China
• Hubei Key Laboratory of Regional Ecology and Environmental Change, China University of Geosciences, Wuhan, China
• Shenzhen Research Institute, China University of Geosciences, Shenzhen, China
• Department of Atmospheric and Environmental Sciences, University at Albany, State University of New York, Albany, NY, USA
• State Key Laboratory of Earth System Numerical Modeling and Application, Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing, China
• Glenn Department of Civil Engineering, Clemson University, Clemson, SC, USA
• Department of Compound Environmental Risks, Helmholtz Centre for Environmental Research—UFZ, Leipzig, Germany
• Department of Civil and Environmental Engineering, Michigan State University, East Lansing, MI, USA
• Department of Geography and Resource Management, The Chinese University of Hong Kong, Shatin, China
• State Key Laboratory of Eco-Hydraulics in Northwest Arid Region of China, Xi’an University of Technology, Xi’an, China
• School of Water Conservancy, North China University of Water Resources and Electric Power, Zhengzhou, China
• National Engineering Research Center of Geographic Information System, School of Geography and Information Engineering, China University of Geosciences, Wuhan, China

Short Summary

This study introduces a Lagrangian four-dimensional tracking framework to identify "deep droughts" (more extensive moisture deficits in deep than surface soils) and reveals their increasing duration and intensity globally over the past four decades due to anthropogenic climate change, with projections for further exacerbation under higher-emission scenarios.

Objective

• To investigate the spatiotemporal evolution and anthropogenic exacerbation of soil moisture droughts, particularly focusing on their vertical structure, by identifying and characterizing "deep droughts" that are often overlooked by surface-based monitoring.

Study Configuration

• Spatial Scale: Global.
• Temporal Scale: Historical analysis from 1981 to 2020 (past four decades); future projections from 2015 to 2100 (specifically 2061–2100 for some projections) under different Shared Socioeconomic Pathways (SSPs).

Methodology and Data

• Models used:
  • Climate models from CMIP6 (Coupled Model Intercomparison Project Phase 6).
• Data sources:
  • Reanalysis datasets: ERA5-Land (hourly total water content of soil layer, near-surface air temperature, precipitation; 1981-2020), GLDAS-Noah (3-hourly total water content of soil layer, near-surface air temperature, precipitation; 1981-2020), CRA-Land (3-hourly total water content of soil layer, near-surface air temperature, precipitation; 1981-2020).
  • Satellite-based soil moisture: GLEAM (daily root-zone and surface soil moisture; 1981-2020), ESA-CCI (daily surface soil moisture; 1981-2020).
  • Ground-based observations: OzNet, ISMN (International Soil Moisture Network).
  • Vegetation data: GLOBMAP (Leaf Area Index - LAI).
  • Drought severity maps: USDM (US Drought Monitor).
  • Land use/cover: MCD12C1.
  • Precipitation data: GSWP-3.
  • Methodology: Lagrangian four-dimensional tracking framework for identifying spatial (horizontal and vertical)–temporal contiguous drought events. Analysis and figure generation performed using Python (v.3.12.2) and R (v.4.2.0).

Main Results

• A novel type of drought, termed "deep droughts," characterized by bottom-heavy deep-dominated shapes (more extensive moisture deficits in deep than surface soils), was identified using a Lagrangian four-dimensional tracking framework.
• Deep droughts account for approximately 25% of total drought events and are largely ignored by conventional surface-based soil moisture monitoring.
• Both reanalysis data and climate models indicate a significant increase in the duration and intensity of deep droughts globally over the past four decades (1981-2020).
• This observed increase in deep drought duration and intensity is attributable to anthropogenic climate change.
• Future projections show that deep droughts are expected to become longer-lasting and more intense globally, with larger increases in deeper soil layers, particularly under higher-emission scenarios (e.g., SSP585).
• These hidden deep droughts pose significant challenges for satellite-based agricultural drought monitoring and lead to an underestimation of adverse impacts on ecosystems.

Contributions

• Introduction of a novel Lagrangian four-dimensional tracking framework to identify and characterize "deep droughts" with distinct vertical soil moisture deficit structures.
• Quantification of the prevalence and increasing trend of deep droughts, revealing that they constitute a significant portion (one-quarter) of total drought events and are largely overlooked by conventional surface-based monitoring.
• Attribution of the observed increases in deep drought duration and intensity over the past four decades to anthropogenic climate change.
• Provision of future projections for deep droughts, highlighting their exacerbation under climate change, particularly in deeper soil layers and under higher-emission scenarios.
• Emphasizing the critical implications of deep droughts for agricultural monitoring and ecosystem impact assessment, addressing a gap in current drought research.

Funding

• National Natural Science Foundation of China (grant nos. U2340230, 42371041 and 42461144214)
• Natural Science Foundation of Shenzhen City, Guangdong Province, China (grant no. JCYJ20240813114059026)
• Key R&D Program of Hubei province, China (grant no. 2023DJC154)
• ‘CUG Scholar’ Scientific Research Funds at China University of Geosciences (Wuhan) (project no. 2022166)
• National Science Foundation (Grant #AGS-2015780 & 2528650)

Citation

@article{Guan2025Anthropogenic,
  author = {Guan, Yansong and Gu, Xihui and Dai, Aiguo and Zhou, Tianjun and Yuan, Xing and Mishra, Ashok K. and Zscheischler, Jakob and Pokhrel, Yadu and Wang, Lunche and Li, Jianfeng and Huang, Shengzhi and Luo, Sijia and Li, Liangwei and Kong, Dongdong and Zhang, Xiang},
  title = {Anthropogenic enhancement of subsurface soil moisture droughts},
  journal = {Nature Climate Change},
  year = {2025},
  doi = {10.1038/s41558-025-02458-z},
  url = {https://doi.org/10.1038/s41558-025-02458-z}
}

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