What Drives Precipitation Intensification During Zonal Atmospheric Rivers Landfalling in the Extratropical Andes?

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Abstract The extratropical Andes, a hotspot for landfalling atmospheric rivers (ARs), are prone to extreme precipitation and related hydrological hazards, including floods and landslides. An improved understanding of the drivers of precipitation intensification during AR landfall is critical for hazard preparedness. Focusing on 50 zonally elongated ARs (ZARs), we demonstrate that precipitation amplification over the Andes is largely associated with strong ascent produced by orographic lifting of ZAR flow and further strengthened by the release of atmospheric instabilities. The efficient realization of these instabilities is linked to large surface relative humidity, , particularly over regions with steep elevation gradients. We further demonstrate that ZAR‐related moisture convergence and terrain‐modulated heat advection in these regions lead to an increase in over the steep Andean terrain. This study emphasizes that accurately estimating precipitation intensification and its spatial distribution during ZAR landfall requires an improved understanding of both moisture and heat transport to the extratropical Andes.

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