Zhang et al. (2026) Changes and driving factors of compound droughts in China based on the soil-atmosphere compound drought index

Identification

• Journal: Journal of Hydrology Regional Studies
• Year: 2026
• Date: 2026-01-07
• Authors: Wei Zhang, Anzhou Zhao, Xianfeng Liu, Lidong Zou, Yahui Wang, Xiaoran Han
• DOI: 10.1016/j.ejrh.2026.103109

Research Groups

• School of Mining and Geomatics Engineering, Hebei University of Engineering, Handan, China.
• School of Geography and Tourism, Shaanxi Normal University, Xi’an, China.
• School of Artificial Intelligence, Shenzhen Polytechnic University, Shenzhen, China.

Short Summary

This study develops the Soil-Atmosphere Compound Drought Index (SACDI) to quantify the concurrent stress of low soil moisture and high vapor pressure deficit across China from 1982 to 2020. The research identifies a transition from drought intensification to alleviation after 2007, driven primarily by temperature fluctuations and atmospheric circulation anomalies.

Objective

• To construct a unified index (SACDI) for assessing the severity of soil-atmosphere compound droughts.
• To characterize the spatiotemporal evolution (frequency, duration, intensity, and severity) of compound droughts across China’s major river basins.
• To identify the dominant climatic, environmental, and anthropogenic driving factors of these events.

Study Configuration

• Spatial Scale: National scale (China), subdivided into nine major river basins: Songhua and Liaohe (SLRB), Haihe (HHRB), Huai (HRB), Yellow (YRB), Yangtze (YTRB), Pearl (PRB), Southeast (SERB), Southwest (SWRB), and Continental River Basin (CRB).
• Temporal Scale: 1982–2020; analyzed at monthly, seasonal, and annual resolutions.

Methodology and Data

• Models and Indices:
  • SACDI: Developed using the empirical Gringorten plotting position formula to integrate Soil Moisture (SM) and Vapor Pressure Deficit (VPD).
  • Run Theory: Used to extract drought characteristics (frequency, duration, intensity, and severity).
  • Trend Analysis: Theil-Sen slope estimation, Mann-Kendall test, and Piecewise Linear Regression.
  • Attribution: Random Forest regression and Partial Correlation Analysis.
• Data sources:
  • Soil Moisture: Fused dataset (ERA5-Land, MERRA-2, and CFSR) at 0.1° resolution.
  • Meteorological Data: ERA5-Land (Temperature, Dew Point, Surface Pressure, Precipitation, Evapotranspiration).
  • Vegetation/Human Activity: GIMMS NDVI, Southern Oscillation Index (SOI), and Nighttime Light (NTL) data.

Main Results

• Evolutionary Phases: Compound droughts followed three distinct phases: intensification (1982–1991; slope = −0.0235/a, $p < 0.05$), fluctuation (1992–2006), and significant alleviation/wetting (2007–2020; slope = 0.0529/a, $p < 0.01$).
• Spatial Heterogeneity: The Continental River Basin (CRB) and Songhua and Liaohe River Basin (SLRB) are hotspots for prolonged hydrological stress, whereas the Huai River Basin (HRB) and Haihe River Basin (HHRB) experience high-frequency but short-duration events.
• Driving Factors: National-scale variability is primarily driven by Temperature (22.92%), Atmospheric Circulation/SOI (22.09%), and Precipitation (17.73%).
• Regional Dynamics: Soil moisture is the dominant control in humid regions (e.g., Yangtze and Pearl River Basins), while atmospheric drought (VPD) is the primary driver in the arid northwestern regions.

Contributions

• New Metric: Introduction of the SACDI, a non-parametric index that captures the interactive nature of soil and atmospheric drought better than univariate indices like SPEI.
• Spatiotemporal Insights: Quantitative mapping of compound drought characteristics at the basin scale, revealing that while frequency has increased in some periods, overall severity has weakened in recent years due to wetting trends.
• Mechanistic Understanding: Clarification of the shifting dominance between soil moisture and atmospheric demand across different climatic zones in China.

Funding

• National Natural Science Foundation of China (No. 42171212).
• Science Research Project of Hebei Education Department (No. JCZX2026037).

Citation

@article{Zhang2026Changes,
  author = {Zhang, Wei and Zhao, Anzhou and Liu, Xianfeng and Zou, Lidong and Wang, Yahui and Han, Xiaoran},
  title = {Changes and driving factors of compound droughts in China based on the soil-atmosphere compound drought index},
  journal = {Journal of Hydrology Regional Studies},
  year = {2026},
  doi = {10.1016/j.ejrh.2026.103109},
  url = {https://doi.org/10.1016/j.ejrh.2026.103109}
}

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