Tong et al. (2025) Evolution and prediction of drought-flood abrupt alternation in mainland China using an improved index

Identification

• Journal: Climate Dynamics
• Year: 2025
• Date: 2025-10-01
• Authors: Yuanyuan Tong, Yu Chen, Yanping Qu, Virgílio A. Bento, Hongquan Song, Han Qiu, Wei Shui, Jingyu Zeng, Qianfeng Wang
• DOI: 10.1007/s00382-025-07885-4

Research Groups

• Fujian Provincial Key Laboratory of Remote Sensing of Soil Erosion and Disaster Protection/College of Environment & Safety Engineering, Fuzhou University, Fuzhou, China
• School of Public Administration and Policy, Renmin University of China, Beijing, China
• Research Center on Flood and Drought Disaster Reduction, China Institute of Water Resources and Hydropower Research, Beijing, China
• Instituto Dom Luiz, Faculty of Sciences, University of Lisbon, Lisbon, Portugal
• College of Geography and Environmental Science, Henan University, Kaifeng, China
• Department of Sustainable Earth System Sciences, University of Texas at Dallas, Richardson, TX, USA

Short Summary

This study develops and validates a daily Drought-Flood Abrupt Alternation Index (DFAI) to overcome limitations of monthly indices, revealing increased DFAA frequency and intensity across mainland China from 1961–2022 and projecting intensified events under future climate change scenarios despite stable or decreasing frequency.

Objective

• To develop and validate a daily DFAI and systematically compare its performance with the conventional monthly DFAI in characterizing historical DFAA events.
• To quantify the spatiotemporal patterns and trends of DFAA in mainland China during 1961–2022 using the daily DFAI.
• To project future DFAA spatiotemporal patterns under Shared Socioeconomic Pathways (SSPs).

Study Configuration

• Spatial Scale: Mainland China, analyzed on gridded datasets (0.25° × 0.25° for reanalysis, 0.5° × 0.5° for GCMs).
• Temporal Scale: Historical analysis from 1961 to 2022 (62 years); future projections from 2015 to 2100 (86 years); daily resolution for the improved DFAI.

Methodology and Data

• Models used:
  • Five Global Climate Models (GCMs) from CMIP6: GFDL-ESM4, IPSL-CM6A-LR, MPI-ESM1-2-HR, MRI-ESM2-0, UKESM1-0-LL.
  • Inter-Sectoral Impact Model Intercomparison Project (ISIMIP3b) bias-corrected outputs.
• Data sources:
  • Gridded observational dataset: CN05.1 (daily precipitation, 1961–2022).
  • Reanalysis data: ECMWF Reanalysis v5 (ERA5) (atmospheric variables, 0.25° × 0.25°, 1940–present).
  • Historical disaster records: Yearbook of Meteorological Disasters of China (2003–2020).
  • Shared Socioeconomic Pathways (SSPs): SSP1-2.6, SSP3-7.0, SSP5-8.5.
  • Statistical methods: Modified Mann–Kendall (MK) test with trend-free pre-whitening, Sen’s slope estimator, Wilcoxon rank-sum test.
  • Index: Daily Drought-Flood Abrupt Alternation Index (DFAI) based on the Standardized Precipitation Index (SPI) at a 30-day timescale.

Main Results

• The improved daily DFAI significantly enhances DFAA event detection, accurately identifying event timing and capturing events missed by monthly indices due to precipitation neutralization or events spanning two months.
• Validation against historical disaster records confirmed the superior performance of the daily DFAI.
• The daily DFAI revealed the Southwest Monsoon Convergence Zone as a high-frequency hotspot for DFAA events, a pattern not clearly identified by monthly indices.
• Over 1961–2022, mainland China experienced statistically significant increases in both DFAA frequency and intensity:
  • Drought-to-Flood (DTF) frequency increased by 0.0058 events per year, and intensity increased by 0.0067 per year.
  • Flood-to-Drought (FTD) frequency increased by 0.0048 events per year, and intensity decreased by 0.0038 per year.
• Regional trends varied, with DTF frequency increasing in Northwest desert areas (Region III), and FTD frequency increasing in Northeast humid/semi-humid warm (Region I) and Inner Mongolia steppe (Region II) regions. DTF intensity increased in Regions III, IV (Qinghai-Tibet Plateau), and V (North China humid/semi-humid temperate region), while FTD intensity increased in Regions I, III, and IV.
• Atmospheric circulation analysis showed large-scale DFAA events are driven by rapid transitions between anticyclonic (drought) and cyclonic (flood) anomalies, influenced by the Western Pacific subtropical high and frontal systems.
• Future projections (2015–2100) under SSP scenarios indicate no overall increase in DFAA frequency (stable or decreasing trends), but a consistent and significant intensification of events, particularly under SSP5-8.5, where southeastern China may experience marked increases in DTF intensity.

Contributions

• Developed and validated an improved daily Drought-Flood Abrupt Alternation Index (DFAI) that overcomes the temporal limitations of conventional monthly indices, enabling more precise detection of DFAA event timing and preventing missed events due to neutralization effects.
• Provided a comprehensive spatiotemporal analysis of historical DFAA events (1961–2022) across mainland China, revealing distinct high-frequency zones (e.g., Southwest Monsoon Convergence Zone) previously obscured.
• Quantified long-term trends in DFAA frequency and intensity, showing significant increases nationwide, with regional variations.
• Offered future projections of DFAA patterns under various Shared Socioeconomic Pathways (SSPs), highlighting a shift towards less frequent but more intense events, crucial for future risk assessment.
• Enhanced the scientific basis for developing early warning systems and adaptive strategies to manage compound hydrometeorological hazards in China.

Funding

• National Key Research and Development Program of China [grant number 2023YFC3006604]
• Natural Science Foundation of Fujian Province [grant number 2021J01627]

Citation

@article{Tong2025Evolution,
  author = {Tong, Yuanyuan and Chen, Yu and Qu, Yanping and Bento, Virgílio A. and Song, Hongquan and Qiu, Han and Shui, Wei and Zeng, Jingyu and Wang, Qianfeng},
  title = {Evolution and prediction of drought-flood abrupt alternation in mainland China using an improved index},
  journal = {Climate Dynamics},
  year = {2025},
  doi = {10.1007/s00382-025-07885-4},
  url = {https://doi.org/10.1007/s00382-025-07885-4}
}