The Low-frequency Variation Characteristics And The Synoptic-scale Eddy Role During The Wintertime In Northern Pacific Ocean

By using the NCEP/NCAR daily atmospheric reanalysis data from 1948 to 2016 and various meteorological diagnosis methods,this paper analyzes the low-frequency variation of the atmosphere over the North Pacific in boreal winter and the role of synoptic-scale eddies,and discusses the change of the quasi-stationary wave of the geopotential height in the lower troposphere which is the main influence factor on the travel of the low frequency disturbance.The main conclusions are as follows:The atmospheric low-frequency variation in North Pacific winter are the traveling waves with a period of about 24 days.The low-frequency disturbances originate in the subtropical Middle East Pacific Ocean,and then spread rapidly to the northeast and developed.After reaching the maximum intensity over the Gulf of Alaska,they move westward and finally die out in the northeast of the Eurasian continent.The propagation of this low-frequency oscillation can affect the Aleutian low,NPO,PNA and WP teleconnection pattern in the middle and high latitudes.As the typical mode of the synoptic-scale eddy over the north Pacific in wintertime,the intensity change of the western developing synoptic-scale eddy has significant low frequency characteristics.Along with its intensity variation,the energy of the highfrequency Rossby wave in the south of the vortex central axis disperses to the southeast and gathers over the ocean surface of the subtropical Middle East Pacific,which is in favour of the atmospheric low-frequency disturbance formation.Appears as the quasi-stationary wave of Aleutian low,the quasi-stationary wave of the geopotential height in the lower troposphere of the north Pacific is the main influencing factor of the low frequency disturbance,and the change of its intensity is closely related to the temperature of the warm zone of Alaska bay and the release of heat flux on the surface of the Kuroshio and its extension,there is a positive feedback mechanism between the quasi-stationary wave of Aleutian low and the temperature of the warm zone of Alaska bay.At the same time,the intensity of the quasi-stationary wave of Aleutian low can affect the atmospheric baroclinicity in the middle latitude and the baroclinic energy conversion between the base flow and the transient disturbance,which will affect the latitudinal position of the Pacific storm track.