Changes in the East Asian Cold Season since 2000 |
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Authors: | WEI Ke CHEN Wen and ZHOU Wen |
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Institution: | Center for Monsoon System Research, Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing 100080, Guy Carpenter Asia-Pacific Climate Impact Centre, School of Energy and Environment, City University of Hong Kong, Hong Kong,Center for Monsoon System Research, Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing 100080,Guy Carpenter Asia-Pacific Climate Impact Centre, School of Energy and Environment, City University of Hong Kong, Hong Kong |
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Abstract: | Using NCEP--NCAR reanalysis data and observational data from meteorological
stations in China, the evolution of the East Asian cold season (EACS) and
its long-term changes after 2000 were studied. A monsoon tendency index
(MTI), defined as the temporal difference of the East Asian monsoon index,
indicates that the winter monsoon setup has been postponed in autumn, while
the setup has quickened in early winter. In mid winter, the EACS breakdown
process has accelerated, while it has lingered in late winter. The authors
suggest that the postponement of monsoon setup in autumn may be caused by
strong global warming at the lower levels, which further limits the setup
time period and leads to the quickening of the setup process in early
winter. Meanwhile, a north--south seesaw of temperature tendency change in
China can be observed in December and February, which may be related to
large-scale circulation changes in the stratosphere, characterized by a
polar warming in mid winter and polar cooling in early spring. This linkage
is possibly caused by the dynamical coupling between stratosphere and
troposphere, via the variation of planetary wave activities. In spring, the
speed of the EACS breakdown has decreased, which favors the revival of the
EACS in East Asia. |
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Keywords: | seasonal evolution East Asian winter monsoon stratosphere-troposphere interaction |
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