Wen et al. (2025) Connections and causes of inter-model spread in boreal summer precipitation across monsoon regions in AMIP6 simulations

Identification

• Journal: Scientific Reports
• Year: 2025
• Date: 2025-11-27
• Authors: Na Wen, Kai Huan
• DOI: 10.1038/s41598-025-29928-w

Research Groups

• College of Atmospheric Sciences, Nanjing University of Information Science and Technology, Nanjing, China
• Key Laboratory of Meteorological Disaster of Ministry of Education, Nanjing University of Information Science and Technology, Nanjing, China

Short Summary

This study investigates the interconnections and underlying causes of inter-model variability in boreal summer precipitation across global monsoon regions using historical AMIP6 simulations, identifying the Western North Pacific (WNP) as a key driver of these inter-regional connections. It reveals that WNP precipitation deviations modulate other monsoon systems through atmospheric dynamic processes, including Walker and Hadley circulations and various wave trains.

Objective

• To investigate the interconnections and underlying causes of inter-model variability in boreal summer precipitation across global monsoon regions, particularly focusing on the coherence and mechanisms of coordinated uncertainty in AMIP6 simulations.

Study Configuration

• Spatial Scale: Global monsoon regions, specifically Western North Pacific (10°N–20°N, 110°E–150°E), East Asia (20°N–45°N, 110°E–135°E), South Asia (10°N–33°N, 70°E–105°E), Australia (5°S–20°S, 110°E–150°E), North Africa (5°N–15°N, 30°W–30°E), Somalia (7°S–25°S, 25°E–70°E), South America (5°S–25°S, 70°W–40°W), and North America (5°N–23°N, 110°W–80°W).
• Temporal Scale: Boreal summer (June, July, August) climatological precipitation from 1979 to 2014.

Methodology and Data

• Models used: Historical simulations from 23 AMIP6 (Atmospheric Model Intercomparison Project Phase 6) models.
• Data sources: AMIP6 simulations with prescribed observed sea surface temperatures (SSTs). Model outputs were interpolated to a horizontal resolution of 2.5° × 2.5°. Ensemble means were calculated for all realization members of each model. Empirical Orthogonal Function (EOF) analysis, principal component (PC) indices, composite analyses, Student’s t-test, and wave activity flux (Takaya and Nakamura formulation) were used for analysis.

Main Results

• Substantial inter-model variability in boreal summer precipitation is concentrated in the tropics, with maximum variability exceeding 4 mm/day, and standard deviations exceeding 30% of local climatological precipitation in all monsoon regions.
• Significant connections exist among the leading modes of precipitation inter-model deviations across different monsoon domains, with the Western North Pacific (WNP) emerging as a key driver.
• WNP precipitation deviations modulate adjacent monsoon systems (South Asian, North African, Australian) primarily through the Walker and Hadley circulations.
• WNP precipitation anomalies, via jet stream disturbances originating from the tropical Indian Ocean, indirectly generate zonal wave trains in the mid-to-high latitudes of both hemispheres, influencing the Somali and South American monsoons.
• The WNP also affects East Asian monsoon precipitation mainly through meridional wave trains along the East Asian coast, triggered by perturbations in the monsoon trough.
• WNP monsoon region shows strong correlations with other regions: East Asia (0.44), South Asia (0.43), Australia (0.53), North Africa (0.55), Somali (0.62 for 3rd mode), and South America (0.4 for 1st mode), all statistically significant at 90% or 95% confidence levels.
• The North American monsoon region exhibits relatively weaker and more independent linkages compared to the WNP.

Contributions

• This study uniquely investigates the interconnections and underlying mechanisms of inter-model spread in boreal summer precipitation across global monsoon regions, moving beyond previous regional-focused analyses.
• By using AMIP6 simulations, it constrains precipitation errors to atmospheric model deficiencies, simplifying the identification of underlying causes compared to coupled models.
• It identifies the Western North Pacific as a critical "engine" region whose precipitation deviations drive a coordinated global pattern of monsoon inter-model variability through specific atmospheric teleconnection pathways.
• The findings highlight the crucial need for improving model performance in simulating precipitation over the WNP to enhance the fidelity of global monsoon simulations.

Funding

• National Key R&D Program of China (2020YFA0608901)

Citation

@article{Wen2025Connections,
  author = {Wen, Na and Huan, Kai},
  title = {Connections and causes of inter-model spread in boreal summer precipitation across monsoon regions in AMIP6 simulations},
  journal = {Scientific Reports},
  year = {2025},
  doi = {10.1038/s41598-025-29928-w},
  url = {https://doi.org/10.1038/s41598-025-29928-w}
}