Increases in Future AR Count and Size: Overview of the ARTMIP Tier 2 CMIP5/6 Experiment

Area of Science:

• Atmospheric science
• Climate modeling
• Hydrology

Background:

• Atmospheric Rivers (ARs) are critical for global weather and water cycles.
• Quantifying uncertainties in AR detection is vital for climate change impact studies.

Purpose of the Study:

• To assess the impact of Atmospheric River Detector (ARDT) uncertainties on scientific understanding of ARs.
• To analyze ARTMIP Tier 2 experimental design and initial results using CMIP5/6 ensembles.

Main Methods:

• Utilized Coupled Model Intercomparison Project (CMIP) Phases 5 and 6 multi-model ensembles.
• Compared AR statistics from various ARDTs against MERRA-2 reanalysis for historical and future simulations.

Main Results:

• AR statistics from CMIP5/6 simulations align well with MERRA-2 reanalysis.
• Most ARDTs project increased global AR frequency, counts, and sizes in future climate scenarios, particularly on western coastlines.
• ARDT choice is the primary source of uncertainty in projected AR frequency, exceeding climate model uncertainty.

Conclusions:

• The selection of an ARDT is a dominant factor in projecting future AR changes.
• Future research on ARs must incorporate ARDT uncertainty into experimental designs.
• This study highlights the need for standardized AR detection methods or explicit uncertainty quantification.