Summer Westerly Jet in Northern Hemisphere during the Mid-Holocene: A Multi-Model Study

The upper-level jet stream, a narrow band of maximum wind speed in the mid-latitude westerlies, exerts a considerable influence on the global climate by modulating the transport and distribution of momentum, heat and moisture. In this study by using four high-resolution models in the Paleoclimate Mo...

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Bibliographic Details
Published in:Atmosphere
Main Authors: Xu, Chuchu, Yan, Mi, Ning, Liang, Liu, Jian
Format: Report
Language:English
Published: MDPI 2020
Subjects:
mid-latitude westerly jet stream
mid-Holocene
multi-model simulation
mechanisms
LAST GLACIAL MAXIMUM
INTERANNUAL VARIABILITY
POLEWARD SHIFT
CLIMATE-CHANGE
STORM TRACKS
WINTER
ASSOCIATIONS
CIRCULATION
SENSITIVITY
SIMULATION
Meteorology & Atmospheric Sciences
Arctic
Pacific
Climate change
North Atlantic
Online Access:http://ir.ieecas.cn/handle/361006/15607
https://doi.org/10.3390/atmos11111193
Description
Summary:The upper-level jet stream, a narrow band of maximum wind speed in the mid-latitude westerlies, exerts a considerable influence on the global climate by modulating the transport and distribution of momentum, heat and moisture. In this study by using four high-resolution models in the Paleoclimate Modelling Intercomparison Project phase 3, the changes of position and intensity of the northern hemisphere westerly jet at 200 hPa in summer during the mid-Holocene (MH), as well as the related mechanisms, are investigated. The four models show similar performance on the westerly jet. At the hemispheric scale, the simulated westerly jet has a poleward shift during the MH compared to the preindustrial period. The warming in arctic and cooling in the tropics during the MH are caused by the orbital changes of the earth and the precipitation changes, and it could lead to the weakened meridional temperature gradient and pressure gradient, which might account for the poleward shift of the westerly jet from the thermodynamic perspective. From the dynamic perspective, two maximum centers of eddy kinetic energy are simulated over the North Pacific and North Atlantic with the north deviation, which could cause the northward movement of the westerly jet. The weakening of the jet stream is associated with the change of the Hadley cell and the meridional temperature gradient. The largest weakening is over the Pacific Ocean where both the dynamic and the thermodynamic processes have weakening effects. The smallest weakening is over the Atlantic Ocean, and it is induced by the offset effects of dynamic processes and thermodynamic processes. The weakening over the Eurasia is mainly caused by the dynamic processes.

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