Chen et al. (2025) Propagation of meteorological to agricultural flash droughts using a novel weekly index

Identification

• Journal: Journal of Hydrology Regional Studies
• Year: 2025
• Date: 2025-12-13
• Authors: Si Chen, Jiaojiao Wu, Jiahao Liu, Mudassar Iqbal, Xiaolan Li, Hai Liu, Muhammad Waseem, Zhe Luo
• DOI: 10.1016/j.ejrh.2025.102973

Research Groups

• School of Resources and Environmental Science, Hubei University, Wuhan, China
• Hubei Key Laboratory of Regional Development and Environmental Response, Hubei University, Wuhan, China
• Centre of Excellence in Water Resources Engineering, University of Engineering and Technology, Lahore, Pakistan
• School of Artificial Intelligence, Shenzhen Polytechnic University, Shenzhen, China

Short Summary

This study introduces a novel weekly Flash Drought Index (FDI) based on soil moisture to effectively monitor and assess agricultural flash droughts in China's Yangtze River basin. It reveals an increasing frequency and severity of these events from 1961 to 2020, and quantifies their propagation characteristics, including lag times and probabilities, from meteorological droughts.

Objective

• Develop a novel weekly Flash Drought Index (FDI) using soil moisture variations to capture the rapid onset and progression of flash droughts effectively.
• Validate the performance of the proposed index against conventional drought indicators such as the Standardized Precipitation Index (SPI) and the Daily Drought Detection Map (DDM).
• Analyze the spatial–temporal characteristics, lag times, and propagation probabilities of meteorological-to-agricultural flash droughts across Anhui and Hubei Provinces.

Study Configuration

• Spatial Scale: Anhui and Hubei provinces (108.3°E–119.5°E, 29°N–34.5°N) in China’s Yangtze River basin, covering approximately 346,000 square kilometers.
• Temporal Scale: 1961 to 2020 (60 years) for most data; 1979 to 2018 for temperature data; 2010 to 2020 for DDM validation. Weekly timescale for FDI and SPI calculations.

Methodology and Data

• Models used:
  • Flash Drought Index (FDI): A novel weekly index based on root zone soil moisture percentiles (decline from 60th to 30th percentile within 4 weeks).
  • Standardized Precipitation Index (SPI): Weekly calculation based on 30-day accumulated precipitation.
  • Run theory: Used to define meteorological drought events (SPI values below -0.5 for at least four consecutive weeks).
  • Fisher-Jenks optimal classification algorithm: Applied to determine region-specific severity thresholds for FDI.
  • K-means clustering: Used for regional segmentation of the study area.
  • Mann-Kendall trend test: Applied to evaluate long-term trends in flash drought area and frequency.
  • Partial correlation analysis and multiple linear regression: Used to investigate synergistic variation trends between soil moisture dynamics and climatic factors.
• Data sources:
  • Daily root zone soil moisture data: GLDASCLSM025D (1961–2014) and GLDASCLSM025DA1D (2015–2020) from NASA’s Goddard Space Flight Center and NOAA (0.25° × 0.25° spatial resolution).
  • Daily precipitation data: CHMPRE dataset from 2839 stations across China (1961–2020, 0.25° × 0.25° spatial resolution) from the National Tibetan Plateau Data Center.
  • Daily temperature data: High-resolution dataset (1979–2018, 0.1° × 0.1° spatial resolution, resampled to 0.25° × 0.25°) from the Tibetan Plateau Data Center.
  • Topographic information: ASTER GDEM Version 2.0 Digital Elevation Model (30 meter resolution) from the Geospatial Data Cloud.
  • Daily Drought Detection Map (DDM): From the China Meteorological Administration (since 2010), based on the Meteorological Drought Composite Index (MCI).

Main Results

• The novel weekly FDI demonstrated an overall accuracy rate of 0.69 when compared with SPI, and accurately captured flash drought events when validated against DDM. Accuracy improved with longer FDI timescales (e.g., FDI4 accuracy of 0.89 against SPI).
• From 1961 to 2020, the frequency of agricultural flash droughts steadily increased across all FDI monitoring timescales (FDI1 to FDI4), with the number of detected events rising from 12 to 53.
• Monthly analysis showed that agricultural flash droughts typically peaked in July across most indices, with notable increases from May to June.
• Anhui Province experienced higher frequencies and a larger spatial extent of agricultural flash droughts than Hubei Province, with hotspots identified in northwestern and southwestern Anhui, and central and western Hubei.
• The average lag time for meteorological drought propagation to an agricultural flash drought ranged from 7.0 to 8.1 weeks, with spatial clustering observed for lag times of 6–9 weeks and 9–12 weeks.
• The probability of meteorological drought propagating to agricultural flash drought increased with longer monitoring timescales, peaking at 43.6% under FDI3. Northern Anhui exhibited significantly higher propagation rates, up to 13.5 times higher than Hubei Province.
• Meteorological drought duration and temperature were identified as pivotal determinants of propagation lags, with 91.88% of FDI1 propagation events occurring at mean temperatures ≥25°C.

Contributions

• Introduction of a novel weekly Flash Drought Index (FDI) based on soil moisture dynamics, featuring region-specific classification thresholds optimized by the Fisher-Jenks algorithm and incorporating multiple monitoring intervals (1-4 weeks) for comprehensive assessment.
• Enhanced capability for monitoring and early warning of rapid-onset agricultural flash droughts, addressing limitations of existing indices in capturing short-term, rapid-onset events.
• Quantification of the propagation process from meteorological to agricultural flash droughts, including their spatial-temporal characteristics, lag times, and probabilities in the agriculturally significant Anhui and Hubei Provinces.
• Deeper understanding of flash drought formation mechanisms within the context of meteorological drought dynamics and the influence of meteorological drought characteristics (severity, duration) and temperature on propagation delays.

Funding

• National Natural Science Foundation of China [grant numbers 42201089, 42271318]
• Natural General Program of Natural Science Foundation of Hubei Province [grant number 2025AFB850]
• Shenzhen Science and Technology Program (Grant No. RCBS20210706092255076)
• Research Foundation of Shenzhen Polytechnic University under Grant No. 6023312010K

Citation

@article{Chen2025Propagation,
  author = {Chen, Si and Wu, Jiaojiao and Liu, Jiahao and Iqbal, Mudassar and Li, Xiaolan and Liu, Hai and Waseem, Muhammad and Luo, Zhe},
  title = {Propagation of meteorological to agricultural flash droughts using a novel weekly index},
  journal = {Journal of Hydrology Regional Studies},
  year = {2025},
  doi = {10.1016/j.ejrh.2025.102973},
  url = {https://doi.org/10.1016/j.ejrh.2025.102973}
}