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Large sampling uncertainty when diagnosing the ‘eddy feedback parameter’ and its role in the signal-to-noise paradox
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  • Leo Saffin,
  • Amanda Maycock,
  • Christine M. McKenna,
  • Rémy Bonnet
Leo Saffin
University of Reading

Corresponding Author:[email protected]

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Amanda Maycock
University of Leeds
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Christine M. McKenna
University of Leeds
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Rémy Bonnet
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A too-weak eddy feedback in models has been proposed to explain the signal-to-noise paradox in seasonal-to-decadal forecasts of the winter Northern Hemisphere. We show that the “eddy feedback parameter’ (EFP) used in previous studies is sensitive to sampling and multidecadal variability. When these uncertainties are accounted for, the EFP diagnosed from CMIP6 historical simulations generally falls within the reanalysis uncertainty. We find the EFP is not independent of the sampled North Atlantic Oscillation (NAO). Within the same dataset, a sample containing larger NAO variability will show a larger EFP, suggesting that the link between eddy feedbacks and the signal-to-noise paradox could be due to sampling effects with the EFP. An alternative measure of eddy feedback, the barotropic energy generation rate, is less sensitive to sampling errors and delineates CMIP6 models that have weak, strong, or unbiased eddy feedbacks, but shows little relation to NAO variability.
19 Feb 2024Submitted to ESS Open Archive
28 Feb 2024Published in ESS Open Archive