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Abstract
Diagnostic comparison of the East Asian subtropical jet (EASJ) and polar-front jet (EAPJ) in winter
season is carried out by using the ERA-40 dataset. The large-scale circulation characteristics and synoptic-
scale transient eddy activities (STEAs) associated with the EASJ and EAPJ are examined. The results show
that the EASJ and EAPJ in the upper-level monthly mean data have no clear geographical border, while
the distribution of the numbers of jet cores from the daily data exhibits a distinct boundary at the latitudes
of the northern Tibetan Plateau. The two areas with large numbers of jet cores correspond to the EASJ
and EAPJ regions. The analysis of STEAs over the East Asian region shows a spatial match of STEAs with
the EASJ and EAPJ in winter: the strong EASJ is located within the weak southern branch of the STEA
while the relatively weak EAPJ appears within the active northern branch of the STEA, indicating that
the EAPJ is the jet coexisting with the STEA. Further analysis shows two anomalous modes of the winter
EAPJ: the anomalous anticyclonic/cyclonic circulation and the weakened/strengthened local westerly wind.
The large-scale circulation anomalies in the Northern Hemisphere related to the first mode are concentrated
in the Eurasian mid to high latitudes, and are also influenced by the anomalous circulation in the upstream
area. When the local westerly wind over the EAPJ region is weakened/strengthened, the westerly jet in the
eastern part of the EASJ and that in the western Pacific region show opposite variations. The corresponding
anomalous atmospheric circulation demonstrates the Eurasian (EU) pattern. The EAPJ anomalies are also
closely linked with the STEA anomalies over East Asia. The anomalies in the northern branch of the STEA
propagate as a wave train along its axis into the East Asian coastal waters, and then migrate eastward to
the oceanic region. However, the ones near the southern branch are trapped over the eastern part of East
Asia and its coastal waters at 200 hPa.
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Citation
REN Xuejuan, YANG Xiuqun, ZHOU Tianjun, FANG Jiabei. 2011: Diagnostic Comparison of Wintertime East Asian Subtropical Jet and Polar-Front Jet: Large-Scale Characteristics and Transient Eddy Activities. Journal of Meteorological Research, 25(1): 21-33.
REN Xuejuan, YANG Xiuqun, ZHOU Tianjun, FANG Jiabei. 2011: Diagnostic Comparison of Wintertime East Asian Subtropical Jet and Polar-Front Jet: Large-Scale Characteristics and Transient Eddy Activities. Journal of Meteorological Research, 25(1): 21-33.
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REN Xuejuan, YANG Xiuqun, ZHOU Tianjun, FANG Jiabei. 2011: Diagnostic Comparison of Wintertime East Asian Subtropical Jet and Polar-Front Jet: Large-Scale Characteristics and Transient Eddy Activities. Journal of Meteorological Research, 25(1): 21-33.
REN Xuejuan, YANG Xiuqun, ZHOU Tianjun, FANG Jiabei. 2011: Diagnostic Comparison of Wintertime East Asian Subtropical Jet and Polar-Front Jet: Large-Scale Characteristics and Transient Eddy Activities. Journal of Meteorological Research, 25(1): 21-33.
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