摘要
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 di？erence of the East Asian monsoon index, indi- cates 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.
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 di？erence of the East Asian monsoon index, indi- cates 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.
基金
support provided by the National Basic Research Program of China (973 Program) (Grant No 2010CB428603)
the National Natural Science Foundation of China(Grant No 40805017)
Part of this paper was produced when the first author was visiting the City University of Hong Kong,supported by the City U Strategic Research Grant 7002505
