Future changes of PNA-like MJO teleconnections in CMIP6 models: underlying mechanisms and uncertainty

April 5, 2022

Lead author T.A O’Brien (Department of Earth and Atmospheric Sciences, Indiana University; Climate and Ecosystem Sciences Division, Lawrence Berkeley National Laboratory) and co-authors, including from CW3E, recently published an article titled “Increases in Future AR Count and Size: Overview of the ARTMIP Tier 2 CMIP5/6 Experiment.” The article, published in Journal of Geophysical Research: Atmospheres/Volume 127, Issue 6, contributes to the goals of CW3E’s 2019-2024 Strategic Plan to support Atmospheric River (AR) Research and Applications and Emerging Technologies by exploring how different AR identification methods and climate models may impact the scientific understanding of future ARs in a warmer climate.

This study utilizes the AR Tracking Method Intercomparison Project (ARTMIP), a community effort to systematically assess how the uncertainties from AR detectors (ARDTs) impact our scientific understanding of ARs. O’Brien et al. utilize ARTMIP Tier 2 experiments and the Coupled Model Intercomparison Project (CMIP) Phases 5 and 6 multi-model ensembles to examine projections in future ARs and how these historical simulations compare to the Tier 1 MERRA-2 experiments.

Results from this study show that most ARDTs and simulations project a relatively large increase in AR frequency, size, and number in future simulations. However, O’Brien et al.’s results further show that ARDT design choice is a major contributor to the uncertainty in future changes in AR frequency, indicating these choices can have an impact on the results of climate change studies. Results from this study highlight the importance of understanding the implications of uncertainty for AR-related research and provide critical considerations for future work.

Figure 1: Maps of atmospheric river (AR) frequency (shown as average number of days with AR conditions) annually for the 1981–2010 period. Each column corresponds to a global AR detection algorithm, and the last column represents the average across all AR detection algorithms. The top row corresponds to AR detections on the Modern-Era Retrospective analysis for Research and Applications, Version 2 data set (the Tier 1 Atmospheric River Tracking Method Intercomparison Project experiment) and the second and third rows correspond to AR detections on the CMIP6 MRI-ESM2-0 simulation. White indicates areas where average AR occurrence is fewer than 1 day. (third and fourth rows) Maps of trends in annual AR frequency in the MRI-ESM2-0 simulation (third row) and all models (fourth row), organized by detection algorithm (columns) from 1951 to 2099 (with a few exceptions noted in the text). Trends significant at the 90% level (according to a 2-sided t-test) are indicated by stippling, and trends significant at the 95% level are indicated by cross-hatching.

O’Brien, T. A., Wehner, M. F., Payne, A. E., Shields, C. A., Rutz, J. J., Leung, L.-R., et al. (2022). Increases in future AR count and size: Overview of the ARTMIP Tier 2 CMIP5/6 experiment. Journal of Geophysical Research: Atmospheres, 127, e2021JD036013.https://doi.org/10.1029/2021JD036013.