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

T A O'Brien; M F Wehner; A E Payne; C A Shields; J J Rutz; L-R Leung; F M Ralph; A Collow; I Gorodetskaya; B Guan; J M Lora; E McClenny; K M Nardi; A M Ramos; R Tomé; C Sarangi; E J Shearer; P A Ullrich; C Zarzycki; B Loring; H Huang; H A Inda-Díaz; A M Rhoades; Y Zhou

doi:10.1029/2021JD036013

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

J Geophys Res Atmos. 2022 Mar 27;127(6):e2021JD036013. doi: 10.1029/2021JD036013. Epub 2022 Mar 21.

Authors

T A O'Brien^{1

2}, M F Wehner³, A E Payne⁴, C A Shields⁵, J J Rutz⁶, L-R Leung⁷, F M Ralph⁸, A Collow^{9

10

11}, I Gorodetskaya¹², B Guan¹³, J M Lora¹⁴, E McClenny¹⁵, K M Nardi¹⁶, A M Ramos¹⁷, R Tomé¹⁷, C Sarangi^{7

18}, E J Shearer¹⁹, P A Ullrich¹⁵, C Zarzycki¹⁶, B Loring³, H Huang², H A Inda-Díaz^{2

15}, A M Rhoades², Y Zhou²

Affiliations

¹ Department of Earth and Atmospheric Sciences Indiana University Bloomington IN USA.
² Climate and Ecosystem Sciences Division Lawrence Berkeley National Laboratory Berkeley CA USA.
³ Computational Research Division Lawrence Berkeley National Laboratory Berkeley CA USA.
⁴ Department of Earth and Space Sciences University of Michigan Ann Arbor MI USA.
⁵ National Center for Atmospheric Research Boulder CO USA.
⁶ National Weather Service, Western Region Headquarters Science and Technology Infusion Division Salt Lake City UT USA.
⁷ Atmospheric Sciences and Global Change Division Pacific Northwest National Laboratory Richland WA USA.
⁸ Center for Western Weather and Water Extremes Scripps Institution of Oceanography University of California, San Diego La Jolla CA USA.
⁹ Universities Space Research Association Columbia MD USA.
¹⁰ Global Modeling and Assimilation Office NASA Goddard Space Flight Center Greenbelt MD USA.
¹¹ Now at University of Maryland Baltimore County Baltimore MD USA.
¹² Centre for Environmental and Marine Studies Department of Physics University of Aveiro Aveiro Portugal.
¹³ Joint Institute for Regional Earth System Science and Engineering University of California, Los Angeles Los Angeles CA USA.
¹⁴ Department of Earth and Planetary Sciences Yale University New Haven CT USA.
¹⁵ Department of Land, Air and Water Resources University of California, Davis Davis CA USA.
¹⁶ Department of Meteorology and Atmospheric Science Pennsylvania State University University Park PA USA.
¹⁷ Instituto Dom Luiz (IDL) Faculdade de Ciências Universidade de Lisboa Lisboa Portugal.
¹⁸ Department of Civil Engineering Indian Institute of Technology Madras Chennai India.
¹⁹ Center for Hydrometeorology and Remote Sensing University of California, Irvine Irvine CA USA.

Abstract

The Atmospheric River (AR) Tracking Method Intercomparison Project (ARTMIP) is a community effort to systematically assess how the uncertainties from AR detectors (ARDTs) impact our scientific 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 the MERRA-2 reanalysis. In CMIP5/6 future simulations, most ARDTs project a global increase in AR frequency, counts, and sizes, especially along the western coastlines of the Pacific and Atlantic oceans. We find 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.

Keywords: ARTMIP; CMIP; atmospheric river; climate change; extreme precipitation.