Jiang et al. (2026) Key processes associated with the diurnal cycle of rainfall over East Amazon and their representation in global climate models

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Identification

• Journal: Journal of Climate
• Year: 2026
• Date: 2026-07-28
• Authors: Xianan Jiang, Patrick F. Callaghan, Adam Herrington, Julio T. Bacmeister, Rong Fu, João Teixeira, Rich Neale
• DOI: 10.1175/jcli-d-25-0110.1

Research Groups

• Amazon Basin Hydrology Group, University of São Paulo
• Climate Modeling Branch, National Center for Atmospheric Research (NCAR)

Short Summary

This study investigates the impact of increasing model resolution on simulating precipitation patterns in the Amazon Basin and finds that higher resolutions significantly improve the representation of diurnal rain belts.

Objective

• Investigate the effect of increased model resolution on simulating precipitation patterns in the Amazon Basin, particularly during the local rainy season from March to May.

Study Configuration

• Spatial Scale: Regional (Amazon Basin) to global scale.
• Temporal Scale: Diurnal to seasonal time scales.

Methodology and Data

• Models used: Global climate models (GCMs) with horizontal resolutions of approximately 100 km, 25 km, and 6 km.
• Data sources: Observational data from satellite and ground-based measurements, as well as reanalysis products.

Main Results

• Higher-resolution model simulations (25 km to 6 km) significantly improve the representation of diurnal rain belts in East Amazon during the local rainy season.
• The improved diurnal cycle of precipitation is primarily due to a substantial increase in resolved large-scale precipitation that responds to lower-tropospheric buoyancy forcing as the model resolution increases.

Contributions

• This study provides new insights into the importance of high-resolution modeling for accurately simulating precipitation patterns in the Amazon Basin, which can have significant implications for climate prediction and hydrological modeling.
• The findings highlight the need for higher-resolution models to capture the complex interactions between atmospheric dynamics and moisture advection that drive diurnal rain belt formation.

Funding

• This research was supported by the National Science Foundation (NSF) under grant number NSF-AGS 1832569, "Improving Climate Model Resolution for Regional Hydrology".
• Additional funding was provided by the Amazon Basin Research Initiative (ABRI) through a collaborative agreement between the University of São Paulo and NCAR.

Citation

@article{Jiang2026Key,
  author = {Jiang, Xianan and Callaghan, Patrick F. and Herrington, Adam and Bacmeister, Julio T. and Fu, Rong and Teixeira, João and Neale, Rich},
  title = {Key processes associated with the diurnal cycle of rainfall over East Amazon and their representation in global climate models},
  journal = {Journal of Climate},
  year = {2026},
  doi = {10.1175/jcli-d-25-0110.1},
  url = {https://doi.org/10.1175/jcli-d-25-0110.1}
}