Wang et al. (2026) Tropical Pacific Sea Surface Temperature Gradient Biases Shape Present‐Day and Future Precipitation Projections Over Southern Hemisphere Midlatitudes

⚠️ Warning: This summary was generated from the abstract only, as the full text was not available.

Identification

• Journal: Geophysical Research Letters
• Year: 2026
• Date: 2026-01-07
• Authors: Liping Wang, Kevin M. Grise
• DOI: 10.1029/2025gl120299

Research Groups

Not specified in abstract

Short Summary

This study investigates how biases in tropical Pacific sea surface temperature (SST) gradient simulations within CMIP6 models affect present-day and future winter precipitation, particularly over South America. It finds that these biases significantly influence South American precipitation via a Pacific–South American (PSA‐2) mode, and applying observational constraints can reduce projection uncertainties by approximately 31%.

Objective

• To assess how biases in the simulated tropical Pacific sea surface temperature (SST) gradient across CMIP6 models influence present-day and future winter precipitation patterns, specifically over mid-latitude populated regions like South America, Tasmania, and New Zealand.

Study Configuration

• Spatial Scale: Tropical Pacific, South America (especially northern Argentina), Tasmania, and New Zealand.
• Temporal Scale: Present-day and future winter precipitation trends.

Methodology and Data

• Models used: CMIP6 models.
• Data sources: Observational constraints (implied for comparison and uncertainty reduction).

Main Results

• Biases in the simulated tropical Pacific SST gradient across CMIP6 models significantly influence present-day and future winter precipitation over South America.
• This influence occurs through a stationary wave pattern resembling the Pacific–South American (PSA‐2) mode.
• Models with a weaker-than-observed SST gradient simulate a deeper trough east of South America, leading to stronger wetting trends over northern Argentina.
• Applying observational constraints reduces uncertainties in projected precipitation trends over South America by approximately 31%.
• For Tasmania and New Zealand, SST gradient biases impact the simulation of present-day winter precipitation but are not well correlated with future precipitation projections.

Contributions

• Highlights the critical need for accurate representation of the tropical Pacific SST gradient and its associated atmospheric circulation features for reliable regional climate simulation.
• Quantifies the reduction in uncertainty (approximately 31%) for projected South American precipitation trends by applying observational constraints.

Funding

Not specified in abstract

Citation

@article{Wang2026Tropical,
  author = {Wang, Liping and Grise, Kevin M.},
  title = {Tropical Pacific Sea Surface Temperature Gradient Biases Shape Present‐Day and Future Precipitation Projections Over Southern Hemisphere Midlatitudes},
  journal = {Geophysical Research Letters},
  year = {2026},
  doi = {10.1029/2025gl120299},
  url = {https://doi.org/10.1029/2025gl120299}
}