PERSISTENT ANOMALY IN URAL AREA IN SUMMER AND ITS BACKGROUND CIRCULATION CHARACTERISTICS

A definition method of persistent anomaly (PA in brief) is proposed based on Dole (1983), and it can be used for global analysis of anomaly circulation. The global distribution of PA is calculated by use of Re-analysis dat a of NCEP/NCAR (Jun. 1 to Aug. 31, 1980-1998) and the characteristics and evolution of background circulation of the PA over Ural area, which have long duration and maybe emerge repeatedly, are studied specially. It is concluded: (1) The definition method of PA proposed in this paper is suitable to analyze global PA; (2) Positive/Negative PA backg round circulation and their development have no symmetry, the development process of negative PA is not contrary to positive PA simply. The development of + PA is related to the movement to northeast of pert urbation and to the west ward movement of positive anomaly over mid-Siberia, which have equivalent barotropic struct ure and will merge as to the set up of + PA over Ural, while-PA results mainly from the development of local negative anomaly over Ural; (3) Barot ropic process may be plays an important role in formation of PA, as is evidently different from PA over north Pacific; (4) There exists obvious difference not only in mid-latitudes of Northern Hemisphere, but also in tropics, high-latitudes and polar area of bi-Hemisphere. (5) Upper-Jet in mid-latitudes is benefit to the set up of PA before PA begins.