Ji et al. (2025) Distinct Hadley circulation attributable to rapid and slow El Niño decay and its regional impacts

Identification

• Journal: npj Climate and Atmospheric Science
• Year: 2025
• Date: 2025-10-13
• Authors: Xuanliang Ji, Juan Feng, Jianping Li, Yazhou Zhang
• DOI: 10.1038/s41612-025-01221-7

Research Groups

• State Key Laboratory of Remote Sensing Science, Faculty of Geographical Science, Beijing Normal University, Beijing, China
• Beijing Engineering Research Center for Global Land Remote Sensing Products, Faculty of Geographical Science, Beijing Normal University, Beijing, China
• State Key Laboratory of Satellite Ocean Environment Dynamics, National Marine Environmental Forecasting Center, Beijing, China
• Key Laboratory of Research on Marine Hazards Forecasting, Ministry of Natural Resources, Beijing, China
• Frontiers Science Center for Deep Ocean Multi-spheres and Earth System/Key Laboratory of Physical Oceanography/Academy of the Future Ocean, Ocean University of China, Qingdao, China
• Laoshan Laboratory, Qingdao, China

Short Summary

This study reveals that rapid decay (RD) El Niño events induce an equatorially asymmetric global Hadley Circulation (HC), contrasting with the quasi-symmetric structure during slow decay (SD) events. These distinct HC configurations, driven by anomalous sea surface temperatures in the central-eastern Pacific, lead to opposing regional precipitation impacts across the Indo-Pacific Warm Pool coastal countries.

Objective

• To investigate how different El Niño decay rates (rapid vs. slow) distinctly influence the global and regional Hadley Circulation (HC) and their associated regional climate impacts, particularly on precipitation patterns.

Study Configuration

• Spatial Scale: Global, with a focus on tropical meridional circulation. Specific regions include the Central-Eastern Pacific (CEP), Indo-Pacific Warm Pool (IPWP, 39° to 139°E), and Atlantic (ATL, 90°W–39°E). Regional climate impacts are analyzed for South Asia, China, Australia, and the Maritime Continent.
• Temporal Scale: Analysis of 25 El Niño events from 1950 to 2022. Specific datasets cover periods like 1950-2022 (ERA5, NCEP1, GPCC, ERSST5), 1958-2022 (JRA55), 1950-2015 (NOAA-20C), 1979-2022 (GPCP), 1961-2019 (Chinese observation stations), 1950-2019 (CESM2 simulations), and 1950-2013 (CMIP6-AMIP). The primary focus is on annual mean conditions during El Niño decay years.

Methodology and Data

• Models used:
  • Community Atmospheric Model, version 5 (CAM5) for sensitivity experiments.
  • Community Earth System Model version 2 (CESM2) Pacific Pacemaker Ensemble (10 simulations).
  • Coupled Model Intercomparison Project Phase 6-Atmospheric Model Intercomparison Project (CMIP6-AMIP) (13 models).
• Data sources:
  • Reanalysis: European Centre for Medium-Range Weather Forecasts Reanalysis v5 (ERA5), National Centers for Environmental Prediction/National Center for Atmospheric Research Reanalysis 1 (NCEP1), Japanese 55-year Reanalysis (JRA55), National Oceanic and Atmospheric Administration (NOAA-20C) for meridional wind, air temperature, relative humidity, vertical velocity, and sea level pressure.
  • Observation/Satellite: Global Precipitation Climatology Centre (GPCC) for monthly global precipitation, Chinese meteorological observation stations for rainfall records, Global Precipitation Climatology Project (GPCP) for gridded daily rainfall.
  • Oceanic: NOAA Extended Reconstructed Sea Surface Temperature v5 (ERSST5) for sea surface temperature (SST) variations and Niño 3.4 index.

Main Results

• Rapid Decay (RD) El Niño events cause the global Hadley Circulation (HC) to exhibit an equatorially asymmetric configuration, with an anomalous ascending branch near 10°S. In contrast, Slow Decay (SD) events result in a quasi-symmetric HC structure with an anomalous ascending branch at the equator.
• This distinction is primarily driven by HC anomalies in the Central-Eastern Pacific (CEP), influenced by anomalous sea surface temperatures (SSTA) that impact the conversion of atmospheric perturbation potential energy (PPE) to kinetic energy (PKE).
  • During RD events, significant conversion from PPE to PKE occurs over the Indo-Pacific Warm Pool (IPWP) and southern CEP, associated with ascending warm, moist air.
  • During SD events, the conversion process shifts, with PKE to PPE over IPWP and PPE to PKE over CEP, associated with ascending warm, moist air at the equator.
• The regional HC over the IPWP intensifies during RD events and weakens during SD events.
• These contrasting regional HC intensities lead to distinct precipitation patterns:
  • RD events are associated with increased terrestrial precipitation over South Asia (e.g., central India, Bangladesh) and China (e.g., southwestern, central, eastern, and northern China).
  • SD events lead to widespread precipitation suppression across South Asia and a dipole rainfall distribution in eastern China (abundant south of Yangtze, drought north of Yellow River).
  • For Australia and the Maritime Continent, RD events show significantly strengthened precipitation, while SD events exhibit weakened precipitation and severe drought conditions.
• Model simulations (CAM5, CESM2, CMIP6-AMIP) corroborate that SSTA variations in the CEP are a decisive factor influencing global HC anomalies.

Contributions

• Reveals that different El Niño decay rates (rapid vs. slow) lead to distinct global Hadley Circulation (HC) configurations (equatorially asymmetric vs. quasi-symmetric), a previously overlooked modulation.
• Identifies the underlying physical mechanism for these distinct HC responses, linking them to anomalous sea surface temperatures (SSTA) in the Central-Eastern Pacific (CEP) and the conversion of atmospheric perturbation potential energy to kinetic energy.
• Demonstrates contrasting regional HC anomaly patterns in the Indo-Pacific Warm Pool (IPWP) for different decay types and quantifies their direct impacts on regional precipitation patterns across South Asia, China, Australia, and the Maritime Continent.
• Offers a novel perspective for understanding and predicting regional climate impacts associated with varying El Niño decay patterns, particularly highlighting the regional HC as a robust and interpretable predictor for seasonal precipitation.
• Provides insights into potential future precipitation changes in the IPWP vicinity under high-emission scenarios, given projections of longer-duration El Niño events and increased frequency of strong El Niño occurrences.

Funding

• National Natural Science Foundation of China (42222501)
• National Key R&D Program of China (2023YFC3107702, 2022YFC3105102)
• Project of Southern Marine Science and Engineering Guangdong Laboratory (Zhuhai) (SML2024SP023)

Citation

@article{Ji2025Distinct,
  author = {Ji, Xuanliang and Feng, Juan and Li, Jianping and Zhang, Yazhou},
  title = {Distinct Hadley circulation attributable to rapid and slow El Niño decay and its regional impacts},
  journal = {npj Climate and Atmospheric Science},
  year = {2025},
  doi = {10.1038/s41612-025-01221-7},
  url = {https://doi.org/10.1038/s41612-025-01221-7}
}