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CMIP6 model fidelity at simulating large-scale atmospheric circulation patterns and associated temperature and precipitation over the Pacific Northwest

Abstract

The ability of a suite of models contributing to the sixth phase of the Coupled Model Intercomparison Project (CMIP6) to simulate observed large-scale atmospheric circulation patterns over the Pacific Northwest of North America is evaluated. Twelve representative patterns of 500-hPa geopotential height (Z500) anomalies are identified using the self-organizing map method applied to reanalysis. CMIP6 Z500 anomalies from simulations of the historical period are mapped to each reanalysis-derived pattern, and the resulting differences between patterns, as well as differences in frequency of pattern occurrence, are quantified. In general, models are able to simulate the range of Z500 patterns with reasonable fidelity, although model skill varies across the 25-member ensemble. Surface temperature and precipitation anomalies associated with each Z500 pattern are found to also be reasonably simulated by the models, with some biases noted. This boosts confidence that the models are simulating temperature and precipitation patterns for the correct physical reasons. The models exhibit a range of skill at simulating pattern occurrence frequency and pattern persistence, with more agreement in winter than summer. Results indicate that the CMIP6 models are appropriate for assessing future projections of key atmospheric circulation patterns and their impacts on temperature and precipitation over the region.

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Data availability

The data used in this study was obtained from the World Research Climate Program (https://esgf-node.llnl.gov/projects/cmip6/) and the Goddard Earth Sciences Data and Information Services Center (https://disc.gsfc.nasa.gov/datasets?project=MERRA-2).

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Acknowledgements

Partial support for this work was provided by the NASA Enabling Tools for the National Climate Assessment (NCA) Program (GPT, HL, DEW). Partial support was provided by the Modelling Analysis and Prediction Program (PCL). We thank the Regional Climate Model Evaluation System team at JPL for their helpful contributions to this work. We thank Ben Lintner for help with methodology development. We also thank the Portland Water Bureau for providing partial support for GPT and CMA.

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All authors contributed to the study. The first draft of the manuscript was written by Graham P Taylor, and all authors read and approved the final manuscript.

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Correspondence to Graham P. Taylor.

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Taylor, G.P., Loikith, P.C., Aragon, C.M. et al. CMIP6 model fidelity at simulating large-scale atmospheric circulation patterns and associated temperature and precipitation over the Pacific Northwest. Clim Dyn (2022). https://doi.org/10.1007/s00382-022-06410-1

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  • DOI: https://doi.org/10.1007/s00382-022-06410-1