Anthropogenic climate change is expected to strengthen the vertical wind shears at aircraft cruising altitudes within the atmospheric jet streams. Such a strengthening would increase the prevalence of the shear instabilities that generate clear-air turbulence. Climate modelling studies have indicated that the amount of moderate-or-greater clear-air turbulence on transatlantic flight routes in winter will increase significantly in future as the climate changes. However, the individual responses of light, moderate, and severe clear-air turbulence have not previously been studied, despite their importance for aircraft operations. Here, we use climate model simulations to analyse the transatlantic wintertime clear-air turbulence response to climate change in five aviation-relevant turbulence strength categories. We find that the probability distributions for an ensemble of 21 clear-air turbulence diagnostics generally gain probability in their right-hand tails when the atmospheric carbon dioxide concentration is doubled. By converting the diagnostics into eddy dissipation rates, we find that the ensembleaverage airspace volume containing light clear-air turbulence increases by 59% (with an intra-ensemble range of 43%–68%), light-to-moderate by 75% (39%–96%), moderate by 94% (37%–118%), moderate-to-severe by 127% (30%–170%), and severe by 149% (36%–188%). These results suggest that the prevalence of transatlantic wintertime clear-air turbulence will increase significantly in all aviation-relevant strength categories as the climate changes.
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The author is financially supported through a University Research Fellowship from the Royal Society (reference UF130571). He thanks Jenny LIN for her invitation and encouragement to write an article on aviation turbulence. The author acknowledges the modelling groups, the Program for Climate Model Diagnosis and Intercomparison, and the World Climate Research Programme’sWorking Group on Coupled Modelling for their roles in making available the climate model data. Support of this dataset is provided by the Office of Science, US Department of Energy. The constructive comments of four reviewers are gratefully acknowledged.
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Williams, P.D. Increased light, moderate, and severe clear-air turbulence in response to climate change. Adv. Atmos. Sci. 34, 576–586 (2017). https://doi.org/10.1007/s00376-017-6268-2