Response of Atmospheric River Width and Intensity to Aquaplanet Warming: A Detection Algorithm‐ and Background Moisture‐Independent Approach

• Published in: Journal of geophysical research. Atmospheres Vol. 130; no. 13
• Main Authors: Baek, Seung H., McClenny, Elizabeth E., Ullrich, Paul A., Quagraine, Kwesi T., Collins, William D.
• Format: Journal Article
• Language: English
• Published: 16.07.2025
• ISSN: 2169-897X; 2169-8996; 2169-8996
• DOI: 10.1029/2025JD043367

The width of an atmospheric river (AR) is an important parameter when evaluating its impact. Although previous research suggests ARs will widen with global warming, a precise response has been muddled by the large sensitivity of width to a diverse set of AR detection techniques (ARDTs). Here, we propose a methodology that removes the influence of the ARDT by modeling AR‐integrated vapor transport (IVT) profiles as idealized exponential curves with free parameters given by background IVT, intensity above background IVT, and profile width. Notably, our definition for AR profile width does not include any explicit numerical thresholds, relative or absolute, for IVT. We apply our approach to a series of idealized aquaplanet experiments, first with a baseline sea surface temperature (SST) distribution, and then with +2K, +4K, and +6K uniform warming, so as to determine the contributions of each free parameter to AR width. We also apply our approach to high‐resolution atmosphere‐only models forced with SSTs modified to preserve historical variability but following projected warming over 2016–2050. Our results show that contributions to impacts‐relevant AR widening comes primarily from enhancements in background IVT and AR intensity, as opposed to from dynamic width changes. Plain Language Summary Atmospheric rivers (ARs) are filamentary structures of the midlatitudes that can cause extreme precipitation, with the width of an AR crucial to its impact footprint. Most studies project ARs to widen with global warming, but a precise understanding of their response has been muddled by the large sensitivity of AR width to specific AR detection techniques (ARDTs), each with their own sensitivity to warming. In this study, we propose a methodology that largely avoids the influence of the ARDT: we model AR profiles as exponential curves with free parameters given by background integrated vapor transport (IVT), intensity above background IVT, and profile width. We apply our approach to a series of idealized aquaplanet (all‐ocean and no‐land) climate model experiments, first with a baseline sea surface temperature (SST) distribution, and then with increasing levels of uniform warming, so as to determine the contributions of each free parameter to AR width. These results are also supplemented with high‐resolution model experiments that simulate climate conditions under more comprehensive and real‐world conditions than the idealized aquaplanet experiments provide. Our results demonstrate that there is little to no AR widening independent of enhancements in background IVT and AR intensity. Key Points Exponential fits are used to separate atmospheric river (AR) width and intensity from background integrated vapor transport (IVT) With this approach, very little expansion of AR width is found from uniform warming across a series of aquaplanet experiments Contributions to impacts‐relevant AR widening come primarily from enhancements in background IVT and AR intensification