Characterizing the winter concurrent variation patterns of the subtropical and polar-front jets over East Asia

Abstract Seasonal variations of the synoptic-scale transient eddy activity (STEA) and the jet streams over East Asia are examined through analysis of the 40-yr European Centre for Medium-Range Weather Forecasts (ECMWF) Re-Analysis (ERA-40) data. Extracted from the 6-hourly upper-level wind fields, the distribution of the jet core numbers exhibits a distinct geographical border for the East Asian subtropical jet (EASJ) and the East Asian polar front jet (EAPJ) at the latitudes of the northern Tibetan Plateau (TP). In the cool seasons, two branches of the STEA and low-level baroclinicity exist over the East Asian landmass, accompanied by the two-jet state of the EASJ and EAPJ. In the warm seasons, a single jet pattern of the EASJ along the north flank of the TP is accompanied by the weakened STEA over the mid- to high latitudes of East Asia. Further analysis shows two distinct features of the seasonal variations of the STEA over East Asia, compared with that over the North Pacific. First, during the transitional period of April–June, the main STEA band over East Asia migrates northward dramatically, in conjunction with the EAPJ shifting in the same direction. Second, both the upper-level STEA and the lower-level baroclinicity poleward of the TP are prosperous in spring. The relationship between the STEA, baroclinicity, vertical wind shear, and static stability in the EAPJ region in different seasons is further investigated. It is found that in addition to the time-mean wind fields, the rapid increase in the sensible heat flux poleward side of the TP region in spring and the associated boundary layer processes are partially responsible for the spring prosperity of the local baroclinicity and the STEA.

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Dynamics of Interannual Variability in Summer Precipitation over East Asia*

Journal of Climate ◽

10.1175/2011jcli4099.1 ◽

2011 ◽

Vol 24 (20) ◽

pp. 5435-5453 ◽

Cited By ~ 80

Author(s):

Yu Kosaka ◽

Shang-Ping Xie ◽

Hisashi Nakamura

Keyword(s):

East Asia ◽

Interannual Variability ◽

Southern Oscillation ◽

Wave Train ◽

Polar Front ◽

Boreal Summer ◽

Boreal Winter ◽

Temperature Advection ◽

Svd Analysis ◽

Precipitation Anomalies

Abstract The summertime mei-yu–baiu rainband over East Asia displays considerable interannual variability. A singular value decomposition (SVD) analysis for interannual variability reveals that precipitation anomalies over the mei-yu–baiu region are accompanied by in situ anomalies of midtropospheric horizontal temperature advection. Anomalous warm (cool) advection causes increased (decreased) mei-yu–baiu precipitation locally by inducing adiabatic ascent (descent). The anomalous precipitation acts to reinforce the vertical motion, forming a feedback system. By this mechanism, the remotely forced anomalous atmospheric circulation can induce changes in mei-yu–baiu precipitation. The quasi-stationary precipitation anomalies induced by this mechanism are partially offset by transient eddies. The SVD analysis also reveals the association of mei-yu–baiu precipitation anomalies with several teleconnection patterns, suggesting remote induction mechanisms. The Pacific–Japan (PJ) teleconnection pattern, which is associated with anomalous convection over the tropical western North Pacific, contributes to mei-yu–baiu precipitation variability throughout the boreal summer. The PJ pattern mediates influences of the El Niño–Southern Oscillation in preceding boreal winter on mei-yu–baiu precipitation. In early summer, the leading covariability pattern between precipitation and temperature advection also features the Silk Road pattern—a wave train along the summertime Asian jet—and another wave train pattern to the north along the polar-front jet that often leads to the development of the surface Okhotsk high.

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Concurrent variation between the East Asian subtropical jet and polar front jet during persistent snowstorm period in 2008 winter over southern China

Journal of Geophysical Research Atmospheres ◽

10.1002/jgrd.50558 ◽

2013 ◽

Vol 118 (12) ◽

pp. 6360-6373 ◽

Cited By ~ 21

Author(s):

Zhijie Liao ◽

Yaocun Zhang

Keyword(s):

Southern China ◽

East Asian ◽

Polar Front ◽

Subtropical Jet ◽

Polar Front Jet ◽

Concurrent Variation

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Contributions of Different Combinations of the IPO and AMO to the Concurrent Variations of Summer East Asian Jets

Journal of Climate ◽

10.1175/jcli-d-19-0366.1 ◽

2020 ◽

Vol 33 (18) ◽

pp. 7967-7982

Author(s):

Xiucheng Xiao ◽

Danqing Huang ◽

Ben Yang ◽

Jian Zhu ◽

Peiwen Yan ◽

...

Keyword(s):

East Asia ◽

East Asian ◽

Active Regions ◽

Atlantic Multidecadal Oscillation ◽

Atmospheric Model ◽

Polar Front ◽

Reanalysis Data ◽

Boreal Winter ◽

Multilinear Regression ◽

The North

ABSTRACTHuang et al. recently reported that opposite phases of the interdecadal Pacific oscillation (IPO) and the Atlantic multidecadal oscillation (AMO) can affect the shift of the East Asian polar front jet (EAPJ) and the East Asian subtropical jet (EASJ) in the boreal winter. To give a full image of the relationship among the IPO, AMO, and concurrent variation of jets throughout the whole year, this study investigates the changes in summer jets response to the combinations of the IPO and AMO, and mostly focuses on the quantitative analysis in the role of the IPO and AMO. Both of the diagnostic analysis and atmospheric model simulations confirm that combinations of the negative phase of the IPO (“−IPO”) and the positive phase of the AMO (“+AMO”) can significantly enhance the EAPJ and reduce the EASJ in the summer, via the meridional temperature gradient and the Eady growth rate, and vice versa in the “+IPO −AMO” combination. The reanalysis data show that this relationship is particularly evident between the periods of 1999–2014 and 1979–98. Based on the simulations, the multilinear regression has indicated that −IPO plays a more important role than +AMO, particularly for the reduced EASJ. We have further revealed two pathways of the stationary Rossby wave activity anomaly, eastward from the North Atlantic to East Asia along 60°N and westward from the North Pacific to East Asia along 40°N. The two activities are associated with anomalous anticyclone along the active regions between EAPJ and EASJ, and therefore affect the jet variations.

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