Wang et al. (2026) Toward drivers of the interannual variability of warm-season extreme rainfall over the Bohai Rim, China

Identification

• Journal: Theoretical and Applied Climatology
• Year: 2026
• Date: 2026-03-09
• Authors: Jing Wang, Yongxiang Zhang, Yujie Li, Mingcai Li
• DOI: 10.1007/s00704-026-06159-1

Research Groups

• Tianjin Key Laboratory for Oceanic Meteorology, and Tianjin Institute of Meteorological Science, Tianjin, China
• National Climate Center, China Meteorological Administration, Beijing, China
• Tianjin Climate Center, Tianjin, China

Short Summary

This study investigates the climatic drivers and physical mechanisms for interannual variations in warm-season rainfall extremes over the Bohai Rim (BHR) region of China from 1979 to 2022. It reveals that increased extreme rainfall is primarily driven by a zonally oriented dipole circulation pattern and a significant lagged influence of El Niño-like Pacific sea surface temperature warming, which induces a subtropical Western North Pacific Subtropical High (WNPSH)-resembling anomaly gyre.

Objective

• To identify the dominant atmospheric and oceanic drivers responsible for the interannual variability of warm-season extreme rainfall anomalies over the Bohai Rim (BHR), China.
• To elucidate the physical mechanisms linking these drivers, particularly winter Pacific sea surface temperature variability, to warm-season extreme rainfall in the BHR.

Study Configuration

• Spatial Scale: Bohai Rim (BHR), defined as the domain (35°–42°N, 115°–124°E).
• Temporal Scale: 1979–2022 (44 years). Warm season is defined as May to September. Preceding winter (December–February) sea surface temperature anomalies are also analyzed.

Methodology and Data

• Models used:
  • Community Earth System Model (CESM) version 1 (CESM1)
  • CESM1 Large Ensemble Simulations (CESM1LENS) (35 members)
  • CESM1 Pacific Pacemaker Experiment Simulations (CESM1PPES) (20 members)
• Data sources:
  • Daily high-resolution (0.25°×0.25°) precipitation data: CN05.1 (National Climate Centre of the China Meteorological Administration).
  • Monthly atmospheric reanalysis data (2.5°×2.5° resolution): National Centers for Environmental Prediction (NCEP)–Department of Energy (DOE) AMIP-II reanalysis (NCEP-2).
  • Monthly convective available potential energy (CAPE) data: fifth generation European Centre for Medium-Range Weather Forecasts reanalysis (ERA5).
  • Monthly sea surface temperature (SST) data (2.0°×2.0° resolution): National Oceanic and Atmosphere Administration (NOAA) Extended Reconstructed SST (ERSST) version 6 (ERSSTv6).
  • Extreme Rainfall Index (ERIBHR) definition: Daily precipitation exceeding the 90th percentile (> 0.1 mm/day) over more than 40% of BHR grid points. Monthly ERIBHR is the cumulative sum of ERI values for all identified events within that month. Warm-season ERIBHR is the sum of monthly ERIBHR from May to September.
  • Vertically integrated horizontal water vapor transport (WVT) and its divergence (WVTdiv) calculated from surface pressure to 100 hPa.
  • Atmospheric convective instability indicators: Vertical difference in equivalent potential temperature (Δθe 500850) and CAPE.
  • Statistical methods: Regression analysis, Pearson correlation analysis, two-tailed Student’s t-test.

Main Results

• Warm-season extreme rainfall (ER) over the Bohai Rim (BHR) exhibits pronounced interannual variability with an upward linear trend of 7.25 mm ABHR per decade (p-value = 0.15) and an interannual variability (1 standard deviation) of 42.57 mm ABHR.
• Enhanced warm-season BHR ER is primarily associated with a zonally oriented mid-latitude dipolar circulation pattern, featuring a barotropic Western North Pacific Subtropical High (WNPSH)-resembling anticyclonic anomaly to the east of the BHR and a cyclonic anomaly centered south of Lake Baikal to the northwest.
• This circulation configuration promotes the convergence of cold–dry and warm–moist air masses over the BHR, leading to significant atmospheric instability (negative Δθe 500_850 and positive CAPE anomalies) and intensified convection.
• A significant lagged influence of winter (December–February, DJF) El Niño-like Pacific sea surface temperature (SST) warming on subsequent warm-season BHR ER extremes is identified. Positive SST anomalies in the eastern-central equatorial Pacific (ECEP) during DJF are typically followed by above-normal extreme rainfall, with an interannual correlation coefficient of 0.29 (p-value = 0.06).
• This winter ECEP SST warming induces a zonal dipolar SST anomaly pattern over the Indo–western North Pacific sector in the following warm season. This pattern generates low-level easterly anomalies that dynamically force a prominent subtropical WNPSH-resembling anomaly gyre, alongside a weakened mid-latitude cyclonic anomaly south of Lake Baikal.
• The enhancement of warm-season BHR ER primarily results from increased tropical moisture transport and favorable dynamic conditions associated with the WNPSH-resembling anomaly gyre, with a minor contribution from the weakened mid-latitude cyclonic anomaly.
• Experimental verification using CESM1 Pacific pacemaker simulations confirms that DJF El Niño-like SSTAs contribute to increased warm-season ER anomalies mainly through the generation of a WNPSH-resembling anomaly gyre, highlighting a major subtropical influence route.

Contributions

• Provides the first comprehensive analysis of the drivers of warm-season extreme rainfall variability over the Bohai Rim (BHR), a critical economic region in China, using an integrated event-based metric (ERI) that accounts for both spatial extent and precipitation amount.
• Identifies and elucidates a dominant subtropical teleconnection pathway linking winter El Niño-like Pacific SST warming to subsequent warm-season precipitation extremes over the BHR, offering valuable insights for seasonal prediction.
• Details the physical mechanisms, including the Indo-Pacific capacitor effect and the dynamic forcing of a WNPSH-resembling anomaly gyre, through which remote oceanic forcings influence regional extreme rainfall.
• Complements existing research on extreme precipitation in eastern China by focusing on a previously underexplored region and a robust metric, highlighting the regional specificity of extreme rainfall drivers.

Funding

• The Open Project of Tianjin Key Laboratory of Oceanic Meteorology (Project Number 2024TKLOM09)
• Innovation and Development Special Funding of the China Meteorological Administration (Grant No. CXFZ2025J049)

Citation

@article{Wang2026Toward,
  author = {Wang, Jing and Zhang, Yongxiang and Li, Yujie and Li, Mingcai},
  title = {Toward drivers of the interannual variability of warm-season extreme rainfall over the Bohai Rim, China},
  journal = {Theoretical and Applied Climatology},
  year = {2026},
  doi = {10.1007/s00704-026-06159-1},
  url = {https://doi.org/10.1007/s00704-026-06159-1}
}