Extreme atmospheric rivers in a warming climate

Area of Science:

• Climate Science
• Atmospheric Rivers
• Extreme Weather Events

Background:

• Extreme atmospheric rivers (EARs) cause significant precipitation and flooding in midlatitude coastal regions.
• Current climate models, which do not resolve eddies, underestimate EARs by approximately 50%, leading to uncertainties in future projections.

Purpose of the Study:

• To assess the impact of eddy-resolving, high-resolution climate simulations on modeling EARs.
• To project the future changes in EARs under different warming scenarios.

Main Methods:

• Utilized an extensive dataset of eddy-resolving, high-resolution Community Earth System Model (CESM) simulations.
• Analyzed changes in EAR occurrence, intensity (integrated water vapor transport), and precipitation under various temperature warming levels and the Representative Concentration Pathway 8.5 (RCP 8.5) scenario.

Main Results:

• Eddy-resolving models significantly improve EAR simulation, with only a slight ~10% overestimate.
• EARs are projected to increase almost linearly with temperature warming.
• Under RCP 8.5, a global doubling of EAR occurrence, water vapor transport, and precipitation is projected by the end of the 21st century, with landfalling EARs tripling.

Conclusions:

• High-resolution, eddy-resolving models provide a more accurate representation of EARs compared to non-eddy-resolving models.
• Future climate warming will lead to a substantial increase in the frequency and intensity of EARs, exacerbating flood risks.
• The reduced coupling between EARs and storms in a warming climate may impact the predictability of these extreme events.