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Dynamique de variabilité des courants-jets des moyennes latitudes

Abstract : This study investigate the impact of Rossby waves on the tropospheric midlatitude eddy-driven jets using an idealized numerical model. It focuses on the dynamical mechanisms driving the persistence of the main modes of variability: a shifting mode and a pulsing mode. The shifting mode is often found to be the leading mode of variability due to an enhanced persistence caused by a positive feedback of Rossby waves. Two new kinds of negative feedbacks have been found for a shorter time-scale than the more classical feedback which mechanism depends on wave properties. These new mechanisms have also been found in the more realistic set up of reanalysis. The impact of climate change is also investigated using the sensitivity analysis of the model to three key parameters : the meridional gradient of temperature, which leads to longer lasting phases of the shifting mode in the future, the jet mean position, which leads to less persistent shifting mode for poleward shifted jets, and frictional damping, because it is a parameter difficult to tune and which varies between numerical models. In conclusion, two new feedback mechanisms acting on eddy-driven jets variability have been found and theoretical diagnostics have been developed and could be used to probe more realistic data such as future climate simulations and reanalysis.
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  • HAL Id : tel-01900354, version 1

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Loïc Robert. Dynamique de variabilité des courants-jets des moyennes latitudes. Sciences de la Terre. Université Pierre et Marie Curie - Paris VI, 2017. Français. ⟨NNT : 2017PA066220⟩. ⟨tel-01900354⟩

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