PNNL

Abstract

The Atmospheric River (AR) Tracking Method Intercomparison Project (ARTMIP) is a community eort to systematically assess how the uncertainties from AR detectors (ARDTs) and climate models impact our scientic understanding of ARs. This study describes the ARTMIP Tier 2 experimental design and initial results using the Coupled Model Intercomparison Project (CMIP) Phases 5 and 6 multi-model ensembles. We show that AR statistics from a given ARDT in CMIP5/6 historical simulations compare remarkably well with reanalyses. In CMIP5/6 future simulations, most ARDTs project a global increase in AR frequency, counts, and sizes, especially along the western coast lines of the Pacic and Atlantic oceans. We nd that the choice of ARDT is the dominant contributor to the uncertainty in projected AR frequency when compared with model choice. These results imply that new projects investigating future changes in ARs should explicitly consider ARDT uncertainty as a core part of the experimental design.