Analyses of the Northern Hemisphere Circulation Characters during Northeast Cold Vortex Persistence
东北冷涡持续活动时期的北半球500 hPa环流特征分析

Abstract The composition, frequency cumulation and correlation analysis of 500 hPa anomaly field arc respectively studied over the Northern Hemisphere in more and fewer years of the cold vortex activities on the northeastern of East Asia (NCVAEA) in May and summer (JJA). The results indicate that persistent activities are not only closely related lo anomalous general circulation over the Northern Hemisphere in the preceding, current and later periods, hut also are an important part of the anomalous area. The fields in the same period with action of NCVAEA have marked different. The departure field at the same lime (JJA) has an opposite phase in comparison with the main abnormal areas in the last winter (DJF); in other words, there is a tcleconncction on half-year scale between (hem. The 500 hPa departure field is similar to North Pacific Oscillation (NPO). If the field has a positivc-of-phase compared with the last winter (DJF), the weak persistence would be predicted. Conversely, the strong JJA cold vortex would be predicted. The key regions tested are located from middle-high latitudes over East Asia lo the Aleutian Islands and corresponding subtropical areas, the Qinghai-Xizang Plateau close to Pakistan, the Chad Basin of North Africa and the Sahara etc. It follows from this that the NCVAHA persistent activities over middle-high latitudes of East Asia are important characteristics of'lhe Northern Hemisphere general circulation in May and summer (JJA).