Regional Difference of Low Temperature Record-breaking Events in China between 1990s and 2000s and its Possible Mechanisms

Wednesday, 17 December 2014
Xueyuan Kuang, Nanjing University, Nanjing, China
Extreme cold events frequently occur in recent several years and arouse widespread concern. In this study, 17 record-breaking event processes (RBEPs) of low temperature during 1981-2012 are identified by using daily minimum temperature at 1897 meteorological stations in China. The RBEPs of low temperature are mostly located in southern China in 1990s but concentrated in northern China in 2000s, which is largely attributed to different AO pattern between the two decades. Furthermore, four typical RBEPs of low temperature are selected to examine the related synoptic-scale atmospheric circulation changes and eddy kinetic energy transports. In the two RBEPs of low temperature occurring in southern China in 1990s, the continent high pressure over Mongolia area was extremely intensified and the East Asian polar front jet stream was enhanced accompanied with strong synoptic-scale eddy kinetic energy transports. Correspondingly, the cold air masses broke out and unobstructed intruded southward to low latitudes, causing severe cooling effect in southern China. In the other two cases occurring at northern China in 2000s, however, the extremely intensified high pressure located over northern Siberian area, combining with northward enhanced subtropical jet stream, then cold air masses were accumulated and blocked at mid-latitudes, resulting in RBEPs of low temperature in this area.