Coordinated Changes In The Northern Hemisphere Storm Axis In Winter And Its Impact On The Northeast Cold Vortex Anomaly

Based on the daily reanalysis data of the U.S.Environmental Forecast Center and the National Center for Atmospheric Research(NCEP/NCAR),Met Office Hadley Centre SST data,160 station temperature and precipitation station data compiled by the National Climate Center and the circulation index data provided by the United States Climate Prediction Center(CPC)from 1967 to 2017,the spatial and temporal variation characteristics of the three major storm tracks in the northern hemisphere as a whole and the northeast vortex on different time scales during winter are studied by calculating the characteristic indexes of the northern hemisphere storm tracks and the northeast cold vortex structure during winter,harmonic analysis,empirical orthogonal function decomposition(EOF)and other methods.The relationship between the two is analyzed,and the influence mechanism of the northern hemisphere storm tracks anomaly on the northeast cold vortex anomaly is discussed by using singular value decomposition(SVD),regression analysis and other methods.The main conclusions are as follows:(1)There are concurrent variations among the storm tracks in the northern hemisphere during winter and the concurrent variations relationship is more obvious on the interdecadal scale.The EOF decomposition results show that the first mode on the interannual scale is mainly manifested by the North Atlantic storm track moves northeast(southeast),the North Pacific storm track moves left(right),and the intensity of the Siberian storm track strength(weaken).The second mode is mainly manifested by the intensity of the North Atlantic storm track strength(weaken),the Siberian storm track moves east(west)and the North Pacific storm track moves south(north).The interdecadal scale is a little different,the first mode is mainly manifested by the intensity of the Siberian storm track strength(weaken),the North Atlantic storm track moves northeast(southwest),and the North Pacific storm track moves south(north).The second mode is mainly manifested by the intensity of the storm tracks of the two oceans strength(weaken)simultaneously and the Siberian storm track moves south(north).(2)In winter,the northeast cold vortex has significant interannual and interdecadal characteristics,and the interannual component of variance contribution rate of each index is larger;the intensity of cold vortex is positively correlated with longitude and latitude and there is a positive correlation between latitude and longitude.EOF decomposition found that the first mode of interannual scale reflects that the northeast cold vortex in winter has a pair of NorthSouth reverse phase characteristics of the climatic mean position with the south as a positive(negative)anomaly and the north as a negative(positive)anomaly.The overall negative(positive)anomaly area of the second mode reflects the intensity of the cold vortex strength(weaken)at the average climate position.The interdecadal scale is mainly reflected in the first mode,namely,the intensity of the cold vortex strength(weaken)in the average position of the climate reflected by the overall negative(positive)anomaly area.(3)Analyzing the correlation coefficients of the northern hemisphere storm tracks indexes and the northeast cold vortex indexes in winter,it is found that there is a clear relationship between the two systems on the interdecadal scale Further SVD decomposition results reflect that the first mode on the interannual scale is mainly manifested in the correlation between the concurrent changes of the North Pacific storm track and the Siberian storm track and the anomalous position of the northeast cold vortex,that is,when the North Pacific storm track moves west(east)and the Siberian storm track moves east(west)but the intensity of the two strength(weaken)simultaneously,the northeast cold vortex moves to the northeast(southwest).The second mode mainly shows the correlation between the concurrent changes of the North Atlantic storm track and the Siberian storm track and the anomalous intensity of the northeast cold vortex,that is,when the North Atlantic storm track moves south(north)and its intensity strength(weaken)and the intensity of the Siberian storm track strength(weaken),the intensity of the northeast cold vortex strength(weaken).The interdecadal scale is mainly reflected in the first mode,which shows the correlation between the concurrent changes of the three storm tracks and the anomalous intensity of the northeast cold vortex,that is,when the North Atlantic storm track moves south(north),the Siberian storm track moves north(south),and the intensity of the storm tracks of the two oceans strength(weaken)simultaneously,the intensity of the northeast cold vortex strength(weaken).The regression analysis reflects that when the northern hemisphere storm tracks change in different ways on different time scales during winter,they will exhibit different spatial coupling characteristics with the same-phase as jet,teleconnection,sea temperature and other systems,and cause the correspondingly anomalous position or intensity of the northeast cold vortex.