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arXiv · 2609.33072

Baroclinic Annular Mode Modulates Global Atmospheric Rivers and Extreme Precipitation

Yuan-Bing Zhao·Lei Wang·Yi Ming
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Abstract

The Baroclinic Annular Mode (BAM) strongly influences extratropical circulation, yet its role in the global hydrological cycle remains unclear. Using ERA5 reanalysis and a global atmospheric river (AR) database, we show that BAM systematically reorganizes AR occurrence and extreme precipitation in both hemispheres. During high-BAM states, AR frequency increases along the flanks of major storm tracks and decreases near their climatological cores, redistributing preferred AR corridors. Relative AR-frequency changes locally exceed 50%, with the most zonally coherent patterns over the Southern Ocean. Extreme precipitation varies correspondingly, with 99th-percentile precipitation occurrence increasing by more than 50% across broad poleward storm-track regions. A large fraction of these extremes coincide with ARs, and AR-associated extreme precipitation shows similar BAM-related modulations. Low-BAM states show broadly opposite anomalies. These results identify BAM as a key mode linking large-scale circulation to global moisture transport and hydrological extremes.

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Yuan-Bing Zhao, Lei Wang, Yi Ming. 2026-09-27. Baroclinic Annular Mode Modulates Global Atmospheric Rivers and Extreme Precipitation. https://arxiv.org/abs/2609.33072

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