Yang et al. (2025) Extreme multi-source forcings reshape three-dimensional circulation to drive the record-breaking Early-Autumn 2024 heat event over the Yangtze River Basin

Identification

• Journal: Climate Dynamics
• Year: 2025
• Date: 2025-11-24
• Authors: Haihong Yang, Shujuan Hu, Sheng Yao, Ziyang Yu, Wenxin Zhang, Jianjun Peng, Deqian Li
• DOI: 10.1007/s00382-025-07949-5

Research Groups

• Key Laboratory for Semi-Arid Climate Change of the Ministry of Education, College of Atmospheric Sciences, Lanzhou University, Lanzhou, China
• Collaborative Innovation Center for Western Ecological Safety, Lanzhou University, Lanzhou, China
• State Key Laboratory of Tropical Oceanography, South China Sea Institute of Oceanology, Chinese Academy of Sciences, Guangzhou, China

Short Summary

This study investigates the record-breaking early-autumn 2024 heat event over the Yangtze River Basin, revealing it was driven by a synergistic combination of remote warm North Atlantic Sea Surface Temperature anomalies and intense South China Sea convection, which reshaped three-dimensional atmospheric circulation.

Objective

• To characterize the record-breaking September 2024 extreme high temperature event (EHTE) over the Yangtze River Basin (YRB), identify its major influencing factors, and uncover the associated dynamical drivers, focusing on the synergistic role of multi-scale atmospheric circulation anomalies and remote forcings.

Study Configuration

• Spatial Scale: Yangtze River Basin (YRB) in China (100°E–122.5°E, 25°N–35°N), North Atlantic, Caribbean Sea, South China Sea (SCS), and Eurasia.
• Temporal Scale: Focus on the September 2024 event. Datasets span 1979–2024, with a climatological baseline of 1981–2010. Numerical model integrations were averaged over days 25–30.

Methodology and Data

• Models used:
  • Linear Baroclinic Model (LBM) with T21 horizontal resolution and 20 sigma levels.
  • Nonstationary Generalized Extreme Value (GEV) distribution for frequency analysis.
  • Three-pattern decomposition of global atmospheric circulation (3P-DGAC).
• Data sources:
  • ERA5 reanalysis (geopotential height, zonal and meridional wind, surface net shortwave radiation, sensible heat flux, total cloud cover, convective precipitation; 1° × 1° horizontal resolution).
  • NOAA Extended Reconstructed Sea Surface Temperature (ERSST) v5 dataset (monthly SST; 2° × 2° grid).

Main Results

• The September 2024 EHTE over the YRB was record-breaking, with regional mean surface air temperature (SAT) anomalies reaching +3.5 °C and an estimated return period of 110 years.
• The event was driven by a coherent configuration of three-dimensional atmospheric circulation anomalies: a quasi-barotropic anticyclonic anomaly north of the YRB in the upper troposphere, an intensified and northwestward-displaced Western Pacific Subtropical High (WPSH) at mid-to-lower levels, and an anomalous meridional circulation with strong subsidence over the YRB.
• This circulation configuration suppressed cloud cover and increased downward shortwave radiation, leading to enhanced surface net radiation and increased upward sensible heat flux, which ultimately elevated SAT.
• Dynamical tracing and numerical experiments revealed two primary remote forcings:
  • Warm sea surface temperature (SST) anomalies in the North Atlantic and Caribbean (forming a dual warm center) excited a downstream Rossby wave train, contributing to the upper-level anticyclone over the YRB.
  • Intensified convective precipitation over the South China Sea (SCS) induced a negative-phase Pacific–Japan (PJ)-like wave train and descending motion, reinforcing WPSH anomalies and the local meridional overturning circulation.
• Linear Baroclinic Model (LBM) experiments confirmed that Atlantic SST and SCS heating can independently reproduce the corresponding wave trains and circulation anomalies.

Contributions

• This study provides the first comprehensive characterization of the three-dimensional circulation structure and thermodynamic–dynamic feedbacks associated with a record-breaking early-autumn EHTE over the YRB.
• It traces the remote forcing origins of the event to the synergistic effects of dual-warm SST anomalies over the North Atlantic and extreme precipitation over the SCS.
• The research demonstrates how multiple remote forcings can simultaneously trigger distinct teleconnections (Rossby waves, PJ pattern, local meridional overturning) across different spatial and temporal scales, whose three-dimensional synergy ultimately leads to regional climate extremes.
• This framework offers new insights into the mechanisms of extreme heat events, particularly those occurring outside the traditional warm season, and provides a physical basis for improving seasonal climate prediction.

Funding

• Joint Funds of the National Natural Science Foundation of China (U2342205)
• National Natural Science Foundation of China (42375063, 424B2037)
• Fundamental Research Funds for the Central Universities of China (lzujbky-2024-it70)
• Key Natural Science Foundation of Gansu Province (23JRRA1030)

Citation

@article{Yang2025Extreme,
  author = {Yang, Haihong and Hu, Shujuan and Yao, Sheng and Yu, Ziyang and Zhang, Wenxin and Peng, Jianjun and Li, Deqian},
  title = {Extreme multi-source forcings reshape three-dimensional circulation to drive the record-breaking Early-Autumn 2024 heat event over the Yangtze River Basin},
  journal = {Climate Dynamics},
  year = {2025},
  doi = {10.1007/s00382-025-07949-5},
  url = {https://doi.org/10.1007/s00382-025-07949-5}
}