Seasonal variations of the relationship between the North Pacific storm track and the meridional shifts of the subarctic frontal zone

Abstract

This study investigates the seasonally meridional shifts of the subarctic frontal zone (SAFZ) and its relationship with North Pacific storm track (NPST). It is found that the SAFZ is at its southernmost in winter but northernmost in summer, and the maximum standard deviations of the SAFZ meridional position is between 153° E and 163° E, with the maximum amplitude of about 2.5 latitudes. When the SAFZ shifts northward (southward), the NPST moves poleward (equatorward) with the distinct seasonally anomalous patterns, i.e., the NPST meridional displacement is larger in winter and autumn, followed by that in spring, and it is smallest in summer. It is also revealed that the near-surface baroclinicity and baroclinic energy conversion (BCEC) may be responsible for the seasonal variations of the relationship between the NPST and the SAFZ shifts. Accompanied by the northward (southward) shift of the SAFZ, the near-surface baroclinicity zone moves northward (southward) significantly, and more mean available potential energy converts to eddy available potential energy and further transferred to eddy kinetic energy in the northern (southern) part of the NPST, resulting in more pronounced northward (southward) movement of the NPST in winter and autumn. However, the NPST anomalous patterns are relatively weak when the near-surface baroclinicity and BCEC anomalies are small in spring and summer.