Characteristics Of Synoptic Scale And Low-frequency Scale Transient Eddy Activities Over North Pacific In Winter And Their Connections To Atmospheric Circulation And SSTA

Based on atmospheric reanalysis data provided by NCEP,sea surface temperature data provided by NOAA from 1950 to 2015,this paper uses EOF decomposition,regression analysis,sliding t test and wavelet analysis to analyze the temporal and spatial characteristics of synoptic scale and low-frequency scale transient eddy activities in interannual and decadal time scales over the mid latitude North Pacific and their ralated air-sea anomaliess.This paper studies the anomalistic characteristics of dynamic forcing and thermal forcing of synoptic scale and low-frequency scale transient eddy activities associated with the Pacific Decadal Oscillation(PDO)and the North Pacific Gyre oscillation(NPGO)and discusses the variation characteristic of water vapor transport and their relationship with PDO and ENSO in time-mean,low frequency and synoptic scales over the North Pacific in winter time.The effects of different phase combination of PDO and ENSO on Atmospheric River(AR)are studied as well.The main conclusions are as follows:The main change mode of synoptic scale storm track and related air-sea anomalies in the North Pacific winter weather is:when the consistent location of storm track is enhanced(weakened),WP teleconnection and Kuroshio SSTA are closely related.When the eastern storm track is enhanced and southward or weakened and northward,the PNA teleconnection,ENSO and PDO are closely related.What's more,when storm track appears east-west opposite zonal anomaly,it is closely related to WP teleconnection and NPGO.The main mode of 850hPa low frequency atmospheric wind field and its related air sea anomaly type over the North Pacific in winter is:when the low frequency wind field is unipolar anomalous cyclonic/anticyclonic circulation,the teleconnection PNA,ENSO and PDO SST anomalies are closely related.When the low frequency wind field is the North-South dipole type,the teleconnection WP and NPGO SSTA are closely related.When the low frequency wind field shows zonal dipole distribution,it has close relationship between the Kuroshio SSTA and the ENSO signal.In the different phases of PDO and NPGO,the anomalous characteristics of atmospheric forcing and thermal forcing are greatly different between synoptic scale and low-frequency scale transient eddy activities.The dynamic forcing of synoptic scale transient eddy activities plays a dominant role in the change of zonal wind speed,while the thermal forcing of low-frequency scale transient eddy activities plays a major role in maintaining the atmospheric temperature gradient in the mid latitudes.North Pacific region is not only the synoptic scale and low frequency transient eddy activities' active region,but also the key area of transporting water vapor from low latitude to the high latitude even polar region and from mainland to ocean.The characteristics of water vapor transport anomalies among time-mean,low frequency scales and synoptic scale are closely related to PDO and ENSO.Different phase combinations of PDO and ENSO have different effects on the atmospheric River(AR).