Wang et al. (2025) Spatially synchronized structures of global hydroclimatic extremes

Identification

• Journal: Nature Water
• Year: 2025
• Date: 2025-10-28
• Authors: Huimin Wang, Xiaogang He
• DOI: 10.1038/s44221-025-00520-w

Research Groups

• Department of Civil and Environmental Engineering, College of Design and Engineering, National University of Singapore, Singapore

Short Summary

This study develops DOMINO-SEE, a multilayer event-based complex climate network framework, to analyze global synchronizations of meteorological droughts, pluvials, and drought-pluvial 'seesaw' extremes using 67 years of precipitation reanalysis data. It reveals pronounced spatial asymmetries in teleconnected synchronizations, dominated by oceanic regions and southern mid-latitudes, and highlights significant cross-hemisphere seesaw patterns affecting global breadbasket regions.

Objective

• To analyze global synchronizations of meteorological drought, pluvial, and drought-pluvial 'seesaw' extreme events across 0.25° pixel pairs, capturing critical spatial dependencies and antiphase co-occurrences often overlooked by traditional methods.

Study Configuration

• Spatial Scale: Global, 0.25° spatial resolution (approximately 27.7 km at the equator), analyzing 0.66 trillion pixel pairs (815,005 nodes). Focuses on teleconnections (>2,500 km) and regional bundles within 14 major global breadbasket regions.
• Temporal Scale: 67 years (1950–2016), using monthly data (1-month Standardized Precipitation Index, SPI1), with event synchronization analyzed at a seasonal (3-month) timescale.

Methodology and Data

• Models used:
  • Detection of Multilayer Interconnected Occurrences for Spatial Extreme Events (DOMINO-SEE) framework.
  • Multilayer complex climate networks.
  • Event Coincidence Analysis (ECA) for timing-based synchronization measures.
  • Poisson process-based analytical statistical test for significance.
  • Kernel Density Estimation (KDE) with a Gaussian kernel (using Haversine distance) for link abundance.
  • Bootstrap analysis for null model significance testing.
• Data sources:
  • Global Drought and Flood Catalogue (GDFC) for 67-year (1950–2016) global precipitation reanalysis (SPI1 values derived from Princeton Global Forcings version 3).
  • NOAA Extended Reconstructed Sea Surface Temperature (SST) version 5 data.
  • ECMWF Reanalysis v5 (ERA5) for 300-hPa meridional wind velocity.
  • Global agricultural land dataset for cropland and pastureland fractions (from sedac.ciesin.columbia.edu).

Main Results

• Teleconnected synchronizations (>2,500 km) exhibit pronounced spatial asymmetries, with 90% of teleconnection links dominated by oceanic regions and southern mid-latitudes.
• Synchronized droughts and pluvials show threshold-dependent behaviors, transitioning from synoptic-scale localized synchronization to planetary-scale teleconnected synchronization at approximately 2,500 km. Teleconnection links account for 29% of drought and 42% of pluvial synchronizations.
• Synchronized seesaw events are predominantly teleconnected (94% of links), with link frequency increasing significantly beyond 300 km.
• Hemispheric asymmetry in teleconnection links is observed, concentrated in tropical regions (20° S to 20° N) and southern mid-latitudes (40° S to 60° S).
• The spatial extent of breadbasket regions affected by synchronized extremes responds asymmetrically between drought and pluvial synchronizations.
• Two-thirds (67%) of region pairs with significant drought or pluvial synchronization occur within the same hemisphere.
• Nearly 40% (13 out of 33) of cross-hemisphere breadbasket region pairs exhibit significant seesaw synchronizations, affecting at least one-third of their areas.
• Specific hotspots include strong drought synchronization between East Africa and India (70% and 80% area affected, respectively), likely driven by El Niño.
• Strong pluvial synchronization between Australia and South Africa is linked to La Niña and negative Indian Ocean Dipole (IOD) modes.
• Cross-hemispheric seesaw examples include 63% of Canada experiencing droughts synchronized with pluvials over 55% of Argentina, potentially driven by the positive phase of the Pacific Decadal Oscillation (PDO).
• Seesaw synchronizations demonstrate an asymmetric nature between drought-pluvial and pluvial-drought dipoles (e.g., Mexico droughts with Canada pluvials vs. Mexico pluvials with Canada droughts).

Contributions

• Introduces DOMINO-SEE, a novel data-driven framework integrating multilayer complex networks and Event Coincidence Analysis (ECA) to systematically compare global and regional coupling structures of synchronized droughts, pluvials, and seesaws within a unified framework.
• Reveals previously under-evaluated synchronization patterns, such as cross-hemispheric pluvial synchronizations not predicted by classical theories (e.g., Mediterranean and South Africa).
• Uncovers an asymmetric response of antiphase extremes (droughts and pluvials) to teleconnection effects, suggesting they should be evaluated as distinct phenomena rather than assuming symmetric behavior.
• Identifies a comprehensive and underexplored threat to global food security posed by cross-hemisphere seesaw extremes in key breadbasket regions, challenging traditional cross-hemispheric trade practices.
• Provides valuable insights and identifies hotspot region pairs that can inform adaptation strategies, such as diversifying food import sources, to enhance the resilience of agrifood systems to hydroclimatic shocks.

Funding

• National Research Foundation, Singapore
• National Environment Agency, Singapore (Climate Impact Science Research Funding Initiative, award no. CISR-2023-1R-17)

Citation

@article{Wang2025Spatially,
  author = {Wang, Huimin and He, Xiaogang},
  title = {Spatially synchronized structures of global hydroclimatic extremes},
  journal = {Nature Water},
  year = {2025},
  doi = {10.1038/s44221-025-00520-w},
  url = {https://doi.org/10.1038/s44221-025-00520-w}
}

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