Hierro (2026) Decoupling Between South American Low‐Level Jet Intensity and Precipitation Extremes in Southeastern South America

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

Identification

• Journal: International Journal of Climatology
• Year: 2026
• Date: 2026-07-30
• Authors: Rodrigo Hierro
• DOI: 10.1002/joc.70532

Research Groups

Not specified in the provided text.

Short Summary

This study examines the relationship between the South American Low-Level Jet (SALLJ) and extreme precipitation in Southeastern South America, concluding that while the jet significantly boosts the probability of extreme rain, it requires specific upper-level dynamical coupling to trigger convection.

Objective

• To evaluate the efficiency of the SALLJ in triggering extreme precipitation events on daily timescales and identify the dynamical mechanisms that modulate this process.

Study Configuration

• Spatial Scale: Southeastern South America (SESA) and the Amazon region.
• Temporal Scale: Austral summers from 2002 to 2024.

Methodology and Data

• Models used: A detection algorithm based on joint wind speed and vertical shear thresholds; composite analyses.
• Data sources: ERA5 reanalysis and IMERG satellite estimates.

Main Results

• The presence of a SALLJ increases the probability of extreme rainfall by approximately 7 times compared to non-jet days.
• The SALLJ primarily functions as a moisture supplier; the majority of jet days do not result in heavy precipitation.
• Dry SALLJ days are characterized by vertical decoupling, where strong low-level moisture transport is suppressed by mid-tropospheric subsidence linked to a stationary Rossby wave train and the rear flank of an upper-level trough.
• Extreme rainfall events occur only when the SALLJ couples with favorable large-scale dynamics that support deep upward motion.

Contributions

• The study highlights that low-level wind intensity alone is an insufficient predictor for extreme precipitation, arguing that operational forecasting must integrate upper-level dynamic diagnostics to minimize false alarms.

Funding

Not specified in the provided text.

Citation

@article{Hierro2026Decoupling,
  author = {Hierro, Rodrigo},
  title = {Decoupling Between South American Low‐Level Jet Intensity and Precipitation Extremes in Southeastern South America},
  journal = {International Journal of Climatology},
  year = {2026},
  doi = {10.1002/joc.70532},
  url = {https://doi.org/10.1002/joc.70532}
}