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Abstract
In this paper, major features of the upper-tropospheric jet streams simulated by a coupled Climate System
Model BCC_CSM1.1 are evaluated through comparison with the NCEP/NCAR reanalysis. The jet streams
consist of the East Asian subtropical jet (EASJ) and the East Asian polar-front jet (EAPJ). Associated
stationary wave and synoptic-scale transient eddy activities (STEA) are also examined. The results show
that the climatological positions of the westerly jet streams are well captured by BCC?CSM1.1, but with
slight intensity biases. Statistics from the 6-h model outputs reveal that the jet core number (JCN) of ESPJ
is significantly underestimated. Examination of the simulated seasonal evolution of the westerly jet stream
indicates that the model has produced a westward movement of the EASJ core in May, one month earlier
than that in the reanalysis. Analysis of stationary wave activities shows that the overestimated meridional
wind component may have caused considerable enhancement of meridional momentum and heat transport.
The stationary Rossby wave represented by the wave activity flux at the southern flank of the Tibetan
Plateau is favorable to the growth of asymmetric zonal wind and the multiple-center pattern of JCN. Unlike
the stationary wave heat flux transport, the model tends to systematically generate weaker transient heat
flux over East Asia. Further analysis of STEA exhibits a general consistent pattern between the simulation
and the reanalysis, while the intensity of the northern STEA branch associated with the EAPJ is greatly
reduced. The deficiencies of eddy momentum and heat flux transport and accompanied eddy forcing may
contribute to the biases of the simulated upper-tropospheric jet streams, suggesting the potential importance
of midlatitude internal atmospheric dynamics in shaping the tropospheric general circulation, which is not
yet fully and accurately resolved in the current BCC_CSM1.1.
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Citation
XIAO Chuliang, ZHANG Yaocun. 2012: The East Asian Upper-Tropospheric Jet Streams and Associated Transient Eddy Activities Simulated by a Climate System Model BCC_CSM1.1. Journal of Meteorological Research, 26(6): 700-716.
XIAO Chuliang, ZHANG Yaocun. 2012: The East Asian Upper-Tropospheric Jet Streams and Associated Transient Eddy Activities Simulated by a Climate System Model BCC_CSM1.1. Journal of Meteorological Research, 26(6): 700-716.
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XIAO Chuliang, ZHANG Yaocun. 2012: The East Asian Upper-Tropospheric Jet Streams and Associated Transient Eddy Activities Simulated by a Climate System Model BCC_CSM1.1. Journal of Meteorological Research, 26(6): 700-716.
XIAO Chuliang, ZHANG Yaocun. 2012: The East Asian Upper-Tropospheric Jet Streams and Associated Transient Eddy Activities Simulated by a Climate System Model BCC_CSM1.1. Journal of Meteorological Research, 26(6): 700-716.
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