Zhang et al. (2025) Characterizing cold surge induced storm surge in the northern East China Sea: A 60-year hindcast reveals paradoxical trends in surge heights and return levels

Identification

• Journal: Weather and Climate Extremes
• Year: 2025
• Date: 2025-11-21
• Authors: Xuecheng Zhang, Luming Shi, Bingchen Liang, Guoxiang Wu, Zhenlu Wang
• DOI: 10.1016/j.wace.2025.100835

Research Groups

• College of Engineering, Ocean University of China, Qingdao, China
• The State Key Laboratory of Coastal and Offshore Engineering, Ocean University of China, Qingdao, China

Short Summary

This study conducted a 60-year hindcast of 780 cold surge-induced storm events in the northern East China Sea, revealing a paradoxical trend of declining storm surge frequency and magnitude but increasing return levels due to shifts in the surge height distribution.

Objective

• To characterize the spatiotemporal evolution of cold surge-induced storm surges over recent decades in the northern East China Sea.
• To determine the corresponding changes in storm surge return levels and identify contributing factors to these shifts.

Study Configuration

• Spatial Scale: Northern East China Sea, including the Yellow and Bohai Seas, with an average horizontal resolution of approximately 1.2 km in the numerical model.
• Temporal Scale: A 60-year hindcast period from 1960 to 2021, with simulations conducted annually from September to May.

Methodology and Data

• Models used:
  • Delft3D-FLOW model (version 6.03) for hydrodynamic simulations.
  • Generalized Pareto Distribution (GPD) for extreme value analysis and return level estimation.
• Data sources:
  • Atmospheric forcing (10-meter wind speed and mean sea level pressure): ERA5 reanalysis dataset (approximately 30 km spatial resolution, 1-hour temporal resolution).
  • Bathymetry: General Bathymetric Chart of the Oceans (GEBCO) and nautical charts.
  • Tidal constituents: TPXO global tidal model (15 constituents).
  • Seawater density: World Ocean Atlas dataset (constant 1025 kg/m³).
  • Cold surge events: Identified using criteria from Zhang et al. (2024).
  • Tide separation: T_TIDE package.
  • Model validation: In-situ observations from 13 tide gauges.

Main Results

• The western coast of the Bohai Sea, particularly Laizhou Bay (LZB) and Bohai Bay (BHB), experienced the most extreme storm surges, with maximum heights exceeding 2 meters.
• Overall, cold surge-induced storm surges showed a long-term decline in occurrence frequency, annual maxima (approximately 3.5 cm per decade), and maximum spatial influence (1% per decade) over the 60-year period.
• Despite the decline in maximum surge heights, 20-year and 50-year storm surge return levels paradoxically increased in most coastal subregions (e.g., 6–10% for RP20 and 7–12% for RP50 in CJS, BHB, and NYS).
• This paradox is attributed to non-uniform shifts in the surge height distribution: an increased proportion of high-percentile surge events and a decreased occurrence of moderate-percentile surges flattened the upper tail of the probability density curve.
• February exhibited the most intense and widespread storm surges, with the highest median maximum surge and largest influential extent (46.1%).
• Monthly maximum storm surges showed increasing trends in September (3.4 cm per decade) and March (3.2 cm per decade), and a decreasing trend in April (−3.8 cm per decade), aligning with East Asian winter monsoon transitions.
• A consistent shift in high-wind directions from northwesterly (declining) to northeasterly (increasing) contributed to regional variations in surge potential.

Contributions

• Presents the first comprehensive 60-year hindcast and analysis of cold surge-induced storm surges in the northern East China Sea, detailing their spatiotemporal variability and changes in return levels.
• Identifies and explains the paradox of declining maximum surge heights but increasing return levels, attributing it to non-uniform shifts in the storm surge probability distribution.
• Provides novel insights into the evolving nature of cold surge-induced storm surges, which are critical for enhancing coastal disaster management and mitigation strategies.

Funding

• National Science Foundation of China (Grant No. W2411039 and 5220134)
• Natural Science Foundation of Shandong Province, China (Grant No. ZR2022QE126)

Citation

@article{Zhang2025Characterizing,
  author = {Zhang, Xuecheng and Shi, Luming and Liang, Bingchen and Wu, Guoxiang and Wang, Zhenlu},
  title = {Characterizing cold surge induced storm surge in the northern East China Sea: A 60-year hindcast reveals paradoxical trends in surge heights and return levels},
  journal = {Weather and Climate Extremes},
  year = {2025},
  doi = {10.1016/j.wace.2025.100835},
  url = {https://doi.org/10.1016/j.wace.2025.100835}
}