Qin et al. (2025) Remote Influence of Andean Convection on Amazonian Rainfall and Its Mechanisms

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

Identification

• Journal: Journal of Geophysical Research Atmospheres
• Year: 2025
• Date: 2025-10-14
• Authors: Hongchen Qin, Michael S. Pritchard, Christopher R. Terai, Julio T. Bacmeister, Peter Bogenschutz, George N. Kiladis
• DOI: 10.1029/2025jd043465

Research Groups

Not explicitly mentioned in the provided abstract.

Short Summary

This study investigates the Wet Andes-Dry Amazon (WADA) precipitation bias in climate models, demonstrating that Andean convection significantly reduces Amazonian rainfall during austral summer through rapid, weather-timescale atmospheric teleconnections involving moisture budget changes and Kelvin waves.

Objective

• To investigate whether Andean convection contributes to the long-standing Wet Andes-Dry Amazon (WADA) precipitation bias pattern observed in Coupled Model Intercomparison Project Phase 6 (CMIP6) models by reducing Amazonian rainfall.

Study Configuration

• Spatial Scale: Andes, Amazon basin, Andean east flank.
• Temporal Scale: Austral summer (wet season), weather timescale (response detectable within a few hours).

Methodology and Data

• Models used: Community Earth System Model v1.1 (CESM v1.1).
• Data sources: Mechanism-denial experiments conducted using CESM v1.1.

Main Results

• Andean convection significantly reduces precipitation over the Amazon during austral summer.
• This reduction operates on a weather timescale, with effects detectable within a few hours after initial Andean forcing.
• The precipitation response is primarily driven by variations in the moisture budget and moderated by changes in convective available potential energy (CAPE) over the Amazon.
• Changes in total moisture advection over the Amazon are dominated by vertical advection, attributed to discrepancies in the dynamic omega field.
• Andean forcing induces descending anomalies on the Andean east flank.
• Disturbances of wind and geopotential fields over the Andean east flank propagate eastward via Kelvin waves.
• Over the Amazon, descending anomalies and advective drying lead to a reduction of mid-to-high level clouds, an increase of shortwave cloud forcing and surface net radiation, and an enhancement of thermodynamic stability and rainfall reduction.

Contributions

• Provides a novel mechanism for the Wet Andes-Dry Amazon (WADA) precipitation bias in climate models, shifting focus from conventional explanations (convection parameterization, land models) to the role of Andean convection.
• Demonstrates that Andean convection rapidly (on weather timescales) and notably reduces Amazonian precipitation during the austral summer.
• Elucidates the atmospheric teleconnection pathway, including the role of moisture budget changes, convective available potential energy, dynamic omega field, and eastward-propagating Kelvin waves from the Andean east flank to the Amazon.
• Offers insights into the physical processes (descending anomalies, advective drying, cloud changes, radiation balance, thermodynamic stability) that link Andean forcing to Amazonian rainfall reduction.

Funding

Not explicitly mentioned in the provided abstract.

Citation

@article{Qin2025Remote,
  author = {Qin, Hongchen and Pritchard, Michael S. and Terai, Christopher R. and Bacmeister, Julio T. and Bogenschutz, Peter and Kiladis, George N.},
  title = {Remote Influence of Andean Convection on Amazonian Rainfall and Its Mechanisms},
  journal = {Journal of Geophysical Research Atmospheres},
  year = {2025},
  doi = {10.1029/2025jd043465},
  url = {https://doi.org/10.1029/2025jd043465}
}