A deep and cold vortex circulation often occurs over northeast China. Known as the northeast China cold vortex (NCCV), the phenomenon is most active from May to mid-June and can lead to extremely cold local temperatures. This study used rotated principle component analysis to categorize NCCV events into four types, which were characterized by ridges (or blocks) over the following regions: Lake Baikal (BKL), the Yenisei River valley (YNS), the Ural Mountains (UR), and the Yakutsk–Okhotsk region (YO). On the intraseasonal time scale, it was found that BKL- and YNS-type NCCVs formed when the wave train height anomalies originating from the North Atlantic and Europe propagated to East Asia. In contrast, YO- and UR-type NCCVs formed in conjunction with the development of a meridional dipole pattern over northeast Asia. The existence of a blocking-type circulation over the Yakutsk–Okhotsk region favored maintenance of the NCCV circulation for the long-lived (more than 5 days) NCCV events of the four types. The typical circulation over northeast Asia for the long-lived NCCV event was closely associated with wave breaking, whereas the short-lived (3–5 days) event showed only wave propagation. The YNS-type NCCV caused cold surface air temperatures (SAT) not only over northeast China, but also over central and south China, whereas the other three types led only to regional cold SAT anomalies over northeast China. All four types of NCCVs caused a precipitation increase over northeast China, and this effect was broader for the UR- and YO-type NCCVs than that for BKL- and YNS-type NCCVs.

A pre‐existing anticyclonic anomaly over Scandinavia/western Russia played a crucial role in the persistent low temperature event over southern China in January 2008. This anticyclonic anomaly extended eastward along the arctic coast of the Eurasian continent, and then induced the persistent low temperature over southern China. Considering that anticyclonic anomalies over Scandinavia/western Russia rarely extended eastward to central Siberia, the simultaneous presence of this feature along with the vigorous Rossby wave propagation along the African‐Asian jet stream is found to be a fundamental factor in the occurrence of the persistent event. Copyright © 2011 Royal Meteorological Society

Northeast China cold vortex (NCCV) circulation associated with a blocking-type circulation over the Yakutsk/Okhotsk (YO) region brings persistent cool weather over Northeast China from May to mid-June and often causes a considerable reduction of local crop production. This study investigated the dynamic features of the YO-NCCV event on intraseasonal time scale and its relation with climate background circulation through analyzing two typical cases of YO-NCCV events. The first event (E1, from 25 May to 4 June, 2008) selected in this study was a long-lived (12 days) case, while the second event (E2, 16–18 May, 1972) was a short-lived one (only 3 days). Though two typical YO-NCCV events both developed from the southeastward movement of the polar high potential vorticity (PV) air, they showed different life cycle features. In the E1, the formation of the NCCV circulation was associated with the poleward intrusion of two low-PV tongues over the Kamchatka Peninsula and the Ural Mountains. The low-frequency Rossby waves propagating from the Scandinavia Peninsula along the westerly to Northeast China mainly contributed to the maintenance of the NCCV circulation. In contrast, for the E2, the low-PV tongue over the Ural Mountains was absent and the PV field over Eurasian continent exhibited a synoptic wave feature. The transient eddy feedback forcing (TEFF) anomalies contributed greatly to the formation and development of the YO-NCCV circulation. From the climatic view, the circulation anomalies associated with the E1 may be regarded as an intensive development of the climatological mean eddy field on the intraseasonal time scale. Results also show that the YO-NCCV event, among the four main types of NCCV event, was most closely related to the negative phase of western Pacific (WP) pattern.

A pair of northeast-southwest-tilted midtropospheric ridges and troughs on the continental scale was observed to be the key circulation feature common among wintertime extensive and persistent low temperature events (EPLTE) in China. During the persistence of such anomalous circulations, the split flow over the inner Asian continent and the influent flow over the southeastern coast of China correspond well to the expanded and amplified Siberian high with tightened sea level pressure gradients and hence, a strong, cold advection over southeastern China. The western Pacific subtropical high tends to expand northward during the early stages of most EPLTEs.