Study On The Variability Of NAO And Polar Vortex

Using the NCEP/NCAR reanalysis data, the correlative inter-annual and inter-decadal variability of NAO index,PVA index,PVI index of four seasons are studied. The main research achievements are as follows:Changes in winter PVA Index are in anti-phase with that of winter NAO index, and winter PVA index has obvious ascending tendency. All the three indexs have multi-periods. They have accordant inter-annual period of 4-5a and inter-decadal period of 9a. In annual scale, the relationship between NAO and Polar Vortex is that the Polar Vortex is arranged to two poles, and it leans to the Atlantic Ocean while the Pacific Ocean part is weaker. This is typical North Atlantic local NAO distribution; Aroud the year 1988,wintertime NAO index has an abrupt change, and wintertime PVI index has an abrupt change around 1976 which is a little earlier than the abrupt change of NAO Index, and wintertime PVA index dosen't have obvious abrupt change; After the abrupt change of NAO index, the anomaly center north of 60°N moves eastward and becomes stronger. In decadal scale, the Polar Vortex is arranged to three poles, and its obvious centers of variation which surround the global around 40°N are mainly on the anomaly centers of high value. In addition, there is no advantage eccentric structure of the Polar Vortex.Spring NAO index,PVA index and PVI index have ascending tendency, and the ascending tendency of PVA index and PVI index is obvious. Spring NAO index,PVA index and PVI index mainly have inter-decadal period. In annual scale, the relationship between NAO and Polar Vortex is that the Polar Vortex is arranged to multipole distribution. It shows not only as NAO, but also as NPO. In addition, It also behaves in Asia and East part of North America. Spring NAO index has an abrupt change aroud the year 1986. Spring PVA index has an abrupt change around 1978 which is a little earlier than the abrupt change of NAO Index. Spring PVA index has an abrupt change around 1978 which is the same as PVA index. Spring Polar Vortex doesn't has obvious change around the abrupt change of NAO index.Summer NAO index,PVA index and PVI index have ascending tendency, and the ascending tendency of PVA index is obvious. Summer NAO index has multi-periods, while summer PVA index and PVI index mainly have inter-decadal period. In annual scale, the relationship between NAO and Polar Vortex is that the Polar Vortex has eccentric pattern, and it leans to the Atlantic Ocean while the Pacific Ocean part is weaker. Summer NAO index has an abrupt change aroud the year 1991. Summer PVA index has an abrupt change around 1971, while PVI index has an abrupt change around 1982. The time of their abrupt change is not accordant. In decadal scale, the relation between of summer NAO and Polor Vortex is that Polor Vortex dosen't have obvious change.Autumn NAO index,PVA index and PVI index have ascending tendency, and the ascending tendency of NAO index and PVA index is obvious, while PVI index is not obvious. All the three indexs have multi-periods. In annual scale, the relationship between NAO and Polar Vortex is that the Polar Vortex is arranged to two poles, and it leans to the Atlantic Ocean while the Pacific Ocean part is weaker. Autumn PVA index has an abrupt change around 1988. PVA index has an abrupt change around 1986 which is accordant with NAO index. The abrupt change of PVI index is around 1996, which is later. In decadal scale, the relation between of autumn NAO and Polor Vortex is that Polor Vortex dosen't have obvious change.In winter, on inter-decadal scale, not only do the anomaly center at high laticude move eastward, but the NAO as a whole moves eastward slightly. The eastward shift of the NAO anomaly center at high laticude is related to the conversion of the NAO positive phase and negative phase. The eastward shift of jet and storm track may be the cause of the eastward shift of the NAO.