Simulation of the Westerly Jet Axis in Boreal Winter
by the Climate System Model FGOALS-g2

XIAO Chuliang and ZHANG Yaocun

doi:10.1007/s00376-012-2167-8

Impact Factor: 5.8

Volume 30 Issue 3

May 2013

Article Contents

Article > ADVANCES IN ATMOSPHERIC SCIENCES > 2013 > 30(3): 754-765

Simulation of the Westerly Jet Axis in Boreal Winter by the Climate System Model FGOALS-g2

1.
School of Atmospheric Sciences, Nanjing University, Nanjing 210093

doi: 10.1007/s00376-012-2167-8

Abstract
References
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Abstract:
The major features of the westerly jets in boreal winter, consisting of the Middle East jet stream (MEJS), East Asian jet stream (EAJS) and North Atlantic jet stream (NAJS), simulated by a newly developed climate system model, were evaluated with an emphasis on the meridional location of the westerly jet axis (WJA). The model was found to exhibit fairly good performance in simulating the EAJS and NAJS, whereas the MEJS was much weaker and indistinguishable in the model. Compared with the intensity bias, the southward shift of the WJA seems to be a more remarkable deficiency. From the perspective of Ertel potential vorticity, the profiles along different westerly jet cores in the model were similar with those in the reanalysis but all shifted southward, indicating an equatorward displacement of the dynamic tropopause and associated climatology. Diagnosis of the thermodynamic equation revealed that the model produced an overall stronger heating source and the streamfunction quantifying the convection and overturning Hadley circulation shifted southward significantly in the middle and upper troposphere. The two maximum centers of eddy kinetic energy, corresponding to the EAJS and NAJS, were reproduced, whereas they all shifted southwards with a much reduced intensity. A lack of transient eddy activity will reduce the efficiency of poleward heat transport, which may partially contribute to the meridionally non-uniform cooling in the middle and upper troposphere. As the WJA is closely related to the location of the Hadley cell, tropopause and transient eddy activity, the accurate simulation of westerly jets will greatly improve the atmospheric general circulation and associated climatology in the model.
- westerly jet axis, FGOALS, model assessment
References

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[2]	Sun Shuqing, 1985: GRAVITY WAVES ON THE AXIS OF LOW LEVEL JET AND THEIR INSTABILITY, ADVANCES IN ATMOSPHERIC SCIENCES, 2, 112-123. doi: 10.1007/BF03179743
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[7]	ZHANG Lixia* and ZHOU Tianjun, , 2014: An Assessment of Improvements in Global Monsoon Precipitation Simulation in FGOALS-s2, ADVANCES IN ATMOSPHERIC SCIENCES, 31, 165-178. doi: 10.1007/s00376-013-2164-6
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[9]	Xiaowei HONG, Riyu LU, Shuanglin LI, 2018: Asymmetric Relationship between the Meridional Displacement of the Asian Westerly Jet and the Silk Road Pattern, ADVANCES IN ATMOSPHERIC SCIENCES, 35, 389-397. doi: 10.1007/s00376-017-6320-2
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Manuscript History

Manuscript received: 26 July 2012

Manuscript revised: 27 November 2012

通讯作者: 陈斌, bchen63@163.com

1.
沈阳化工大学材料科学与工程学院沈阳 110142

Simulation of the Westerly Jet Axis in Boreal Winter by the Climate System Model FGOALS-g2

1. School of Atmospheric Sciences, Nanjing University, Nanjing 210093

Manuscript received: 2012-07-26
Manuscript revised: 2012-11-27

Abstract: The major features of the westerly jets in boreal winter, consisting of the Middle East jet stream (MEJS), East Asian jet stream (EAJS) and North Atlantic jet stream (NAJS), simulated by a newly developed climate system model, were evaluated with an emphasis on the meridional location of the westerly jet axis (WJA). The model was found to exhibit fairly good performance in simulating the EAJS and NAJS, whereas the MEJS was much weaker and indistinguishable in the model. Compared with the intensity bias, the southward shift of the WJA seems to be a more remarkable deficiency. From the perspective of Ertel potential vorticity, the profiles along different westerly jet cores in the model were similar with those in the reanalysis but all shifted southward, indicating an equatorward displacement of the dynamic tropopause and associated climatology. Diagnosis of the thermodynamic equation revealed that the model produced an overall stronger heating source and the streamfunction quantifying the convection and overturning Hadley circulation shifted southward significantly in the middle and upper troposphere. The two maximum centers of eddy kinetic energy, corresponding to the EAJS and NAJS, were reproduced, whereas they all shifted southwards with a much reduced intensity. A lack of transient eddy activity will reduce the efficiency of poleward heat transport, which may partially contribute to the meridionally non-uniform cooling in the middle and upper troposphere. As the WJA is closely related to the location of the Hadley cell, tropopause and transient eddy activity, the accurate simulation of westerly jets will greatly improve the atmospheric general circulation and associated climatology in the model.

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