Cold surges were unusually active in subtropical East Asia during January-February 2005. These cold surges were preceded by upstream wave trains,which originated in the Mediterranean-Sahara region and propagated eastward along the subtropical jet stream over the Eurasian continent. The northerly of upper-level cyclonic anomaly in East Asia coupled with the low-level northerly upon the arrival of wave activity, followed by the quick southward penetration of cold air mass and surface anticyclone. Diagnostic and numerical results suggest that the anomalously active wave activity affecting the East Asian cold surges may be attributed to the anomalously enhanced jet stream over Middle East and the anomalously westward extended East Asian Jet Stream. The configuration of these two subtropical jet streams established a strong waveguide through which the wave activity forced in the Mediterranean-Sahara region efficiently propagated to East Asia and resulted in more-than-averaged cold surge events in the subtropical East Asia. Wave-like perturbation tended to amplify at the entrance of the East Asian jet through barotropic energy conversion from the mean flow.
如有問題歡迎與系統管理員聯繫 
