Seasonal variation of the North Pacific storm-track relationship with the Subarctic frontal zone intensity

The relationship between the North Pacific storm track and the intensity of the subarctic frontal zone (SAFZ) in each season is investigated in this study. Associated with the strengthened SAFZ, the storm track in winter characterize a distinct downstream intensification, and a comparable enhancement appears in spring in the northwestern part of the storm track; while the storm-track anomalies are much weaker in summer and autumn. It is found that the seasonal variation of the storm-track anomalous patterns may be attributed to the near-surface baroclinicity and the baroclinic energy conversion (BCEC) anomalies. When the SAFZ intensifies in winter (spring), accompanied by the increased near-surface baroclinicity in the central and eastern (northwestern) part of the storm track, more energy is converted form the mean available potential energy to the eddy available potential energy and then transferred to the eddy kinetic energy, which favors the robust downstream (northwestward) enhancement of the storm track in winter (spring). While the weaker storm-track anomalous patterns occur in summer and autumn, due to small near-surface baroclinicity and BCEC anomalies.