Yao et al. (2026) Inter-tropical African precipitation regime shifts dominated by tropical easterly jet

Identification

• Journal: npj Climate and Atmospheric Science
• Year: 2026
• Date: 2026-01-06
• Authors: Shuai-Lei Yao, Renguang Wu, Pengfei Lin, Pao-Shin Chu, Haosu Tang, Pengfei Wang
• DOI: 10.1038/s41612-025-01312-5

Research Groups

• Key Laboratory of Earth System Numerical Modeling and Application, Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing, China
• School of Earth Sciences, Zhejiang University, Hangzhou, China
• College of Earth and Planetary Sciences, University of Chinese Academy of Sciences, Beijing, China
• Department of Atmospheric Sciences, School of Ocean and Earth Science and Technology, University of Hawai'i at Mānoa, HI, USA
• School of Geography and Planning, University of Sheffield, Sheffield, UK

Short Summary

This study reveals that inter-tropical African precipitation regime shifts, characterized by a monopolar drying trend since 1950, are primarily driven by the tropical easterly jet (TEJ) strengthening due to Indo-Pacific warming, with a secondary influence from the intertropical convergence zone (ITCZ). Applying an observational TEJ constraint significantly reduces uncertainty in near-term projections, indicating a higher likelihood of extreme drying under an accelerated TEJ.

Objective

• To identify the primary dynamic drivers of inter-tropical African (ITA) precipitation regime shifts during boreal spring.
• To reduce uncertainty in near-term (2026-2045) precipitation projections for ITA by developing and applying an observational constraint based on the tropical easterly jet (TEJ).

Study Configuration

• Spatial Scale: Inter-tropical Africa (ITA: 12°S-12°N, 16°W-52°E), with some analyses extending to broader tropical and extra-tropical regions for teleconnections.
• Temporal Scale: Historical period (1950-2022) for observations and model evaluations; near-term projections (2026-2045) and future projections (2015-2100) for climate models.

Methodology and Data

• Models used:
  • Coupled Model Intercomparison Project phase six (CMIP6) multi-model ensemble (31 models) for historical and future projections (SSP2-4.5, SSP5-8.5).
  • CESM1 (Community Earth System Model 1) large ensemble (40 runs) and pacemaker experiments (10-member ensembles) for driver analysis.
  • MPI-ESM-LR (Max Planck Institute Earth System Model - Low Resolution) large ensemble (100 runs).
  • Detection and Attribution Model Intercomparison Project (DAMIP) single-forcing simulations (10 CMIP6 models).
• Data sources:
  • Precipitation: ERA5, GPCC v7, CRU TS v4.09, UDEL v5.01, NOAA 20CV3, GPCP v3.2, CMAP, JRA55, MERRA2.
  • Sea Surface Temperature (SST): ERSST v3, HadISST, HadCRUT5, NOAA GlobalTemp.
  • Atmospheric fields: ERA5, JRA55 (for circulation, tropospheric temperature, specific humidity).
  • Methods: Empirical Orthogonal Function (EOF) analysis, atmospheric column-integrated moisture budget analysis, linear regression, 9-year running mean filtering, and a process-based observational TEJ constraint framework.

Main Results

• The observed inter-decadal spring precipitation variability in ITA is dominated by two leading modes: a monopolar pattern (32.2% of total variance) primarily driven by the tropical easterly jet (TEJ) and a dipolar pattern (15.1% of total variance) mediated by the intertropical convergence zone (ITCZ).
• The Indo-Pacific warming-induced strengthening of the TEJ has driven a monopolar drying trend across ITA from 1950 to 2022, primarily through reduced vertical moisture advection via anomalous subsidence.
• A northward-shifted ITCZ, linked to a north-minus-south inter-hemispheric warming contrast, contributes a secondary west drying-east wetting dipolar precipitation pattern.
• Current climate models (CMIP6, CESM1, MPI-ESM-LR) generally project a wetting tendency in ITA and underestimate the observed TEJ strength and its decadal influence on precipitation, leading to high uncertainty in near-term projections.
• Applying an observational TEJ constraint significantly reduces the standard deviation of near-term (2026-2045) precipitation trends across models by 19% to 39.7%.
• Under an accelerated TEJ with an amplitude of -2 standard deviations, the probability of extreme drying trends in ITA could increase almost threefold in the near term (2026-2045). Conversely, a TEJ weakening could lead to a higher likelihood of extreme wetting.

Contributions

• Identifies the tropical easterly jet (TEJ) as the primary dynamic driver of observed decadal precipitation regime shifts (monopolar drying) in inter-tropical Africa (ITA), providing a novel mechanism distinct from previous hypotheses.
• Quantifies the relative contributions of TEJ and ITCZ to ITA precipitation variability, offering a more comprehensive understanding of its complex dynamics.
• Develops and applies an innovative observational TEJ constraint framework that significantly narrows model spread and reduces uncertainty in historical and near-term (2026-2045) precipitation projections for ITA.
• Underscores the critical importance of realistic TEJ simulations for enhancing confidence in future hydroclimate projections across Africa, a region highly vulnerable to precipitation variations.

Funding

• National Key Program for Developing Basic Sciences (2020YFA0608902)
• National Key R&D Program of China (2022YFC3104805)

Citation

@article{Yao2026Intertropical,
  author = {Yao, Shuai-Lei and Wu, Renguang and Lin, Pengfei and Chu, Pao-Shin and Tang, Haosu and Wang, Pengfei},
  title = {Inter-tropical African precipitation regime shifts dominated by tropical easterly jet},
  journal = {npj Climate and Atmospheric Science},
  year = {2026},
  doi = {10.1038/s41612-025-01312-5},
  url = {https://doi.org/10.1038/s41612-025-01312-5}
}