Peng et al. (2025) Ocean-driven shifts in circulation regime frequency modulate South China rainfall

Identification

• Journal: npj Climate and Atmospheric Science
• Year: 2025
• Date: 2025-11-21
• Authors: Dongdong Peng, Tianjun Zhou, Sheng Hu, Jiayu Zheng
• DOI: 10.1038/s41612-025-01244-0

Research Groups

• Guangdong Provincial Key Laboratory of Regional Numerical Weather Prediction, Guangzhou Institute of Tropical and Marine Meteorology, China Meteorological Administration
• State Key Laboratory of Tropical Oceanography, South China Sea Institute of Oceanology, Chinese Academy of Sciences
• State Key Laboratory of Earth System Numerical Modeling and Application, Institute of Atmospheric Physics, Chinese Academy of Sciences

Short Summary

This study reveals that the interannual variability of South China's rainy-season precipitation is primarily driven by shifts in the frequency of daily atmospheric circulation regimes, rather than changes in rainfall intensity. These regime frequency shifts are modulated by remote sea surface temperature (SST) anomalies in the Indian, Pacific, and Atlantic Oceans, which trigger large-scale atmospheric responses over the western North Pacific.

Objective

• To investigate the pathways through which sea surface temperature (SST) anomalies shape regional precipitation variability in South China, focusing on daily atmospheric dynamics.
• To determine whether the interannual variability of South China's rainy-season rainfall is primarily driven by shifts in daily circulation regimes or by changes in rainfall intensity.
• To establish a regime-mediated mechanism linking remote ocean variability to regional hydroclimate extremes, thereby offering new insights for improving climate prediction and projection.

Study Configuration

• Spatial Scale: South China (18–30°N, 105–123°E) for precipitation analysis; broader domain (5°N–45°N, 90°E–140°E) for circulation classification. Global for SST anomaly analysis.
• Temporal Scale: Rainy season (April to September) over the period 1981–2021. Analysis focuses on daily atmospheric dynamics and interannual variability.

Methodology and Data

• Models used:
  • K-means clustering: Applied to 850 hPa horizontal winds for objective classification of daily large-scale circulation patterns.
  • FLEXPART version 9.02: Lagrangian particle diffusion model used for moisture tracking and source diagnostics.
  • ANUSPLIN software: Used to generate the CN05.1 gridded precipitation and temperature dataset.
• Data sources:
  • Observed daily precipitation and temperature: CN05.1 dataset (0.25° × 0.25° resolution, 1961-present).
  • Reanalysis data: Climate Forecast System Reanalysis (CFSR) version 1 and 2 (6-hourly, 0.5° × 0.5° resolution, 1979-present) and Japanese Reanalysis for Three Quarters of a Century (JRA-3Q) (6-hourly, 1.25° × 1.25° resolution, 1947-present).
  • Observed monthly Sea Surface Temperature: Hadley Centre Sea Ice and Sea Surface Temperature dataset (HadISST) version 1.1 (1° × 1° resolution, 1870-present).
  • Daily Outgoing Longwave Radiation (OLR) Climate Data Record (1° × 1° resolution, 1979-present).
  • Tropical cyclone data: International Best Track Archive for Climate Stewardship (IBTrACS) project Version 4r01 dataset.
  • South China Sea Summer Monsoon (SCSSM) onset dates: Provided by the National Climate Center, China Meteorological Administration.
  • Gridded Population and Gross Domestic Product datasets for China in 2020 (1 kilometer resolution).

Main Results

• Four dominant daily circulation regimes (CP1, CP2, CP3, CP4) were objectively identified for the South China rainy season: two low-pressure system (LPS)-related types (CP1: anomalous cyclone over northeastern South China Sea; CP2: anomalous cyclone over western North Pacific), a pre-onset monsoon regime (CP3: anomalous anticyclone over Philippine Islands), and a South China Sea monsoon-dominated regime (CP4: anomalous anticyclone over western North Pacific).
• These regimes account for 20.94% (CP1), 19.78% (CP2), 25.04% (CP3), and 34.24% (CP4) of total rainy-season days, respectively.
• The interannual variability of South China's rainy-season rainfall is primarily driven by shifts in the frequency of these daily circulation regimes, rather than changes in rainfall intensity or the composition of moisture sources.
• SST anomalies in the Indian, Pacific, and Atlantic Oceans modulate these circulation regime frequencies by triggering large-scale atmospheric responses, particularly anomalous cyclones or anticyclones over the western North Pacific (WNPAC/WNPC).
• Specific teleconnections include:
  • Indian Ocean Basin Mode (IOBM) warming and North Atlantic EOF1 (NA-EOF1) lead to an anomalous anticyclone over the western North Pacific (WNPAC), suppressing convection and LPS formation.
  • South Atlantic EOF1 (SA-EOF1) warming triggers a WNPAC north of the Philippine Islands (inhibiting LPSs) and an anomalous cyclone over the southern South China Sea (favoring SCSSM onset).
  • North Pacific EOF2 (NP-EOF2) excites a midlatitude Rossby wave train, inducing a cyclonic anomaly (WNPC) over the western North Pacific, which enhances convection and LPS frequency.
  • El Niño–Southern Oscillation (ENSO) associated SST anomalies weaken the Walker circulation, producing a WNPAC that suppresses convection and delays SCSSM onset.

Contributions

• Introduces a novel regime-mediated mechanism that links remote ocean variability to regional hydroclimate extremes, emphasizing the role of daily atmospheric dynamics.
• Demonstrates that interannual rainfall variability in South China is primarily governed by fluctuations in the frequency of distinct circulation patterns, rather than changes in rainfall intensity or moisture origin within those patterns, challenging previous mean-state analyses.
• Provides a transferable framework for diagnosing hydroclimate variability that can be applied to other regions and climate variables, potentially uncovering hidden teleconnections.
• Offers new insights for improving climate prediction and projection by integrating regime dynamics into climate models, addressing long-standing biases in simulated precipitation variability.

Funding

• Joint Funds of the National Natural Science Foundation of China (U2242203)
• National Natural Science Foundation of China (41905070)
• Guangzhou Basic and Applied Basic Research Foundation (2025A04J4709)
• Guangdong Basic and Applied Basic Research Foundation (2023A1515240067)
• State Key Laboratory of Tropical Oceanography, South China Sea Institute of Oceanology, Chinese Academy of Sciences (Project No. LTO2311)
• China Meteorology Administration Key Innovation Team of Tropical Meteorology (CMA2023ZD08)
• Guangdong Provincial Marine Meteorology Science Data Center (2024B1212070014)

Citation

@article{Peng2025Oceandriven,
  author = {Peng, Dongdong and Zhou, Tianjun and Hu, Sheng and Zheng, Jiayu},
  title = {Ocean-driven shifts in circulation regime frequency modulate South China rainfall},
  journal = {npj Climate and Atmospheric Science},
  year = {2025},
  doi = {10.1038/s41612-025-01244-0},
  url = {https://doi.org/10.1038/s41612-025-01244-0}
}