Legarth et al. (2025) Characteristics of Extreme Precipitation and Flood Producing Atmospheric Rivers in the Alouette Watershed of British Columbia and the Development of a Modified Severity Scale

⚠️ 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: 2025-10-10
• Authors: E. Legarth, Roland B. Stull, Rachel H. White
• DOI: 10.1029/2025jd043453

Research Groups

Not explicitly stated in the abstract.

Short Summary

This study investigated the influence of various Atmospheric River (AR) characteristics on extreme precipitation and streamflow in the Alouette watershed, British Columbia, Canada, identifying key AR features like approach angle, Integrated Water Vapor Transport (IVT), rain-on-snow, and antecedent soil moisture as strong predictors of extreme streamflow, and recommending an enhanced AR severity scale for the region.

Objective

• To study the effects of a range of Atmospheric River (AR) characteristics on extreme precipitation and streamflow in the Alouette watershed, British Columbia, Canada.
• To identify specific AR features that cause extreme flooding in regions outside the US, particularly in Canada, where a national AR severity scale is lacking.

Study Configuration

• Spatial Scale: Alouette watershed, British Columbia, Canada.
• Temporal Scale: Historical analysis of Atmospheric River events (specific period not stated).

Methodology and Data

• Models used: Analysis of AR characteristics and their correlation with extreme events.
• Data sources: ERA5 reanalysis data, Global AR Database (Guan, 2022).

Main Results

• The majority of extreme-event producing ARs (X-ARs) in the Alouette watershed approach the British Columbia coast from compass directions between 210° and 220°.
• ARs approaching from a more westerly direction can cause extreme events with an Integrated Water Vapor Transport (IVT) as low as 400 kg⋅m⁻¹⋅s⁻¹, whereas ARs from a more southerly direction require an IVT exceeding 800 kg⋅m⁻¹⋅s⁻¹.
• IVT, the presence of rain-on-snow events, and high preceding soil moisture conditions are strongly correlated with the production of extreme streamflow in the Alouette watershed.

Contributions

• Provides specific insights into AR characteristics driving extreme flooding in a Canadian coastal watershed, addressing a gap in research outside the US.
• Recommends an enhancement to the existing US AR scale for the Alouette watershed, suggesting the inclusion of surface air temperature, angle of approach, and antecedent conditions for improved hazard calculation.
• Offers a framework for similar analyses in other high-impact watersheds where accurate prediction of AR impacts is crucial.

Funding

Not explicitly stated in the abstract.

Citation

@article{Legarth2025Characteristics,
  author = {Legarth, E. and Stull, Roland B. and White, Rachel H.},
  title = {Characteristics of Extreme Precipitation and Flood Producing Atmospheric Rivers in the Alouette Watershed of British Columbia and the Development of a Modified Severity Scale},
  journal = {Journal of Geophysical Research Atmospheres},
  year = {2025},
  doi = {10.1029/2025jd043453},
  url = {https://doi.org/10.1029/2025jd043453}
}