Cao et al. (2025) China's three major cereal crops exposed to compound drought and extreme rainfall events

Identification

• Journal: Natural hazards and earth system sciences
• Year: 2025
• Date: 2025-12-18
• Authors: Hanming Cao, Yang Qiren, Wei Yang, Zhao Lin
• DOI: 10.5194/nhess-25-5017-2025

Research Groups

• School of Resource and Environmental Sciences, Wuhan University, Wuhan 430079, China

Short Summary

This study investigates the spatiotemporal characteristics and agricultural exposure of compound drought and extreme rainfall (CDER) events in China's nine major agricultural regions. It reveals that CDER are concentrated in the northwest, southwest, and northern regions, peaking in summer, with drought-rainfall events being more frequent and intense, and identifies varying exposure risks for maize (highest), wheat (moderate), and rice (lowest) during their growth stages.

Objective

• To elucidate the spatiotemporal distribution patterns, frequency, and intensity of compound drought and extreme rainfall (CDER) events (drought followed by extreme rainfall, CDER dr; and extreme rainfall followed by drought, CDER rd) across China's nine major agricultural regions.
• To quantify the exposure of China's three major cereal crops (maize, wheat, and rice) to these compound events during their specific growth stages.

Study Configuration

• Spatial Scale: Mainland China, specifically nine major agricultural regions (C1-C9), analyzed at a 1 kilometer (km) grid resolution.
• Temporal Scale: Analysis period for compound events and crop exposure: 2000–2019. Data used spans 1961–2022 for precipitation and 2000–2022 for soil moisture.

Methodology and Data

• Models used:
  • Standardized Soil Moisture Index (SSMI) for drought event identification (values below -1 standard deviation).
  • 99th percentile threshold of precipitation for extreme rainfall identification.
  • Moving average (7-day window) for smoothing soil moisture data.
  • Least Squares Method (LSM) for linear trend fitting.
  • K-Means clustering algorithm for classifying event intensity into five levels.
  • Loess regression for modeling local trends in crop risk evolution.
• Data sources:
  • Soil moisture data: China 1 km Soil Moisture Daily Dataset (2000–2022) based on station observations (National Tibetan Plateau Data Center).
  • Precipitation data: China Daily Precipitation Dataset (1961–2022), CHM_PRE V2 (National Tibetan Plateau/Third Pole Environment Data Center).
  • Crop phenological and planting distribution data: National Three Major Grain Crops 1 km Planting Distribution Dataset (2000–2019) (National Ecological Science Data Center).

Main Results

• Compound drought and extreme rainfall (CDER) events are primarily concentrated in China's northwest, southwest, and northern agricultural regions.
• The impact area of CDER events is largest during summer months (June, July, August).
• CDER dr (drought followed by extreme rainfall) events occur with significantly higher frequency and intensity than CDER rd (extreme rainfall followed by drought) events, with affected area proportions nearly doubling those of CDER rd (e.g., 20% vs 10% in region C1 in July).
• Interannual variation trends in affected areas show regional differences: declining trends in regions C1, C3, C6–C9 (especially post-2010 reductions in C6–C9); upward trends in C2 and C4; and mixed trends in C5.
• Among the three major cereal crops, maize generally exhibits the highest and most variable disaster risk, particularly in regions C4 (Huang-Huai-Hai) and C5 (Loess Plateau), with exposure values reaching up to 60,000.
• Wheat shows moderate risk, concentrated in regions C4 and C5, with CDER dr-induced exposures nearly double those from CDER rd.
• Rice demonstrates the lowest risk with minimal fluctuations, with the highest risks observed in regions C7 (Middle Lower Yangtze River), C8 (Southwest China), and C9 (South China), reaching up to 40,000.
• The risk evolution for all crops across regions generally follows a "first rising and then declining" pattern, with a peak around 2010.
• Interannual exposure variations are primarily driven by intrinsic changes in CDER characteristics rather than adjustments in cultivated area, though planted area can exert a substantial effect for rice.

Contributions

• Provides a comprehensive, national-scale analysis of compound drought and extreme rainfall (CDER) events in China's nine major agricultural regions, addressing a gap in previous provincial-scale studies.
• Innovatively refines crop exposure assessment by focusing on specific crop growth stages (maturity periods) for maize, wheat, and rice, rather than annual time scales, leading to more accurate risk profiles.
• Utilizes soil moisture data to monitor compound events from an agricultural perspective, offering a distinct approach compared to previous studies that primarily used hydrological indices.
• Elucidates the spatiotemporal distribution patterns and evolution characteristics of CDER, offering constructive insights for disaster prevention and mitigation through more refined risk assessments.

Funding

• Third Xinjiang Scientific Expedition Program (2022xjkk0601)
• National Natural Science Foundation of China (42471085 and U22B2011)
• Natural Science Foundation of Hubei Province (2023AFB823)

Citation

@article{Cao2025Chinas,
  author = {Cao, Hanming and Qiren, Yang and Yang, Wei and Lin, Zhao},
  title = {China's three major cereal crops exposed to compound drought and extreme rainfall events},
  journal = {Natural hazards and earth system sciences},
  year = {2025},
  doi = {10.5194/nhess-25-5017-2025},
  url = {https://doi.org/10.5194/nhess-25-5017-2025}
}