The variation of wintertime Kuroshio Extension SST front and its influence on the Pacific storm track

This paper analyzes the variation of wintertime Kuroshio Extension SST front and its influence on the Pacific storm track using NOAA daily Optimum Interpolation Sea Surface Temperature (SST) data and NCEP/NCAR daily atmospheric reanalysis data. Results show that the strength of wintertime Kuroshio Extension SST front has significant interannual to interdecadal variations,and mostly shows interdecadal variation. The interannual and interdecadal variations are independent of each other. The interdecadal variation of the strength of wintertime Kuroshio Extension SST front has significant influences on the Pacific storm track, but the interanual variation doesn't. When the SST front is strong, the baroclinicity significantly decreases over the region from the downstream to the eastern Pacific, and increases over the Okhotsk Sea and the region near Alaska; the baroclinic energy transfer from the mean available potential energy to the eddy available potential energy (BCEC1) increases over the Pacific south of 45°N, and decreases over the Pacific between 35°-45°N; the baroclinic energy transfer from the eddy available potential energy to eddy kinetic energy (BCEC2) significantly increases over the western Pacific north of 35°N and eastern Pacific north of 45°N, and only decreases over the southern adjacent band region, resulting the strengthening of Pacific storm track over the Pacific north of 40°N and the weakening of Pacific storm track over the Pacific south of 40°N,and vice versa. When the position of SST front shifts northward, the baroclinicity over the Pacific south of 45°N weakens, while both BCEC1 and BCEC2 reduce over the central and eastern Pacific south of 45°N, resulting in weakening of the Pacific storm track over the Pacific south of 45°N. Meanwhile, the baroclinicity over the Pacific north of 45°N increases, especially over the region near the Gulf of Alaska. BCEC1 and BCEC2 both significantly increase over the Kuroshio extension and the central and eastern Pacific north of 45°N where the Pacific storm track finally strengthens, and vice versa. Both the strength and position variations of wintertime Kuroshio Extension SST front have significant influences on the Pacific storm track, and the physical mechanisms behind need to be further studied.