The Concurrent Variation Characteristics Of Storm Tracks In The Northern Hemisphere And Its Possible Mechanism

Based on the daily analysis data of National Center for Environmental Prediction/National Center for Atmospheric Research(NCEP/NCAR),the monthly sea surface temperature data,atmospheric and oceanic index data of National Climate Prediction Center(NCPC)during 1971 to 2016,this paper recognizes the three major storm tracks in the mid-latitudes of the northern hemisphere as a whole,and analyzes the climatological characteristics?the concurrent variation characteristics and its possible mechanism of storm tracks on interannual and interdecadal scales by using the index of storm track?regression analysis?Empirical Orthogonal Function(EOF)?the multiscale energy and vorticity analysis(MS-EVA)methods.The results are summarized as follows:(1)The mean state of the climate shows that the kinetic energy source of storm tracks manifests as available potential energy transmission from large-scale to synoptic-scale on the middle and upper reaches of storm tracks,and the subsequent energy conversion from potential to kinetic energy on synoptic-scale in the main areas of storm tracks,But the difference,there is directly energy transmission from large-scale to synoptic-scale in the western part of storm tracks.The kinetic energy dissipation of storm tracks manifests as energy transmission from synoptic-scale to large-scale on the middle and lower reaches of storm tracks,because of the dispersion by ageostrophic potential flux and the downstream effects,that keeps the storm track stay in a constant area.(2)The concurrent variation characteristics of the three major storm track in the northern hemisphere by using the index from a single storm track shows that the longitude index of Siberian storm track(northern Atlantic storm track)has significant positive correlation with intensity(latitude)index on interannual and interdecadal scale,while the latitude(longitude)index of the northern Pacific storm track has a significant positive(negative)correlation with the intensity index on interannual(interdecadal)scale;There also have the concurrent variation characteristics between the three storm tracks,the longitude index of northern Pacific storm track has significant negative correlation with longitude index and intensity index of Siberian storm track,while the intensity index of northern Pacific storm track has significant negative correlation with latitude index of northern Atlantic storm track on interannual scale.And the northern Pacific storm track has significant negative(positive)correlation with the Siberian storm track and northern Atlantic storm track in the longitude(intensity)index,while the northern Pacific storm track has significant negative correlation with the northern Atlantic storm track in the latitude index on interdecadal scale.The concurrent variation characteristics of the three major storm track of the northern hemisphere by using EOF shows that the first mode is mainly a reflection of the intensity change of overall storm tracks,while the Siberian storm track and the northern Pacific storm track weaken(intensify),the northern Atlantic storm track intensify(weaken)on the interannual scale.And the Siberian storm track?the northern Pacific storm track and northern Atlantic storm track weaken(intensify)on the interdecadal scale.But the second mode shows that position variance of overall storm tracks,while the northern Pacific storm track shifts northward(southward),and the Siberian storm track and the northern Atlantic storm track shift southward(northward)on the interannual(interdecadal)scale.(3)Further analysis shows that the abnormality of overall storm tracks in the northern hemisphere has a close association with the large-scale circulation in different modes and different time scales.The fluctuation of large-scale can affect the multiscale energy variation in the area of storm tracks by changing sea temperature and westerly jet,and then affect the anomaly characteristics of overall storm tracks in the northern hemisphere during winter.