Abstract
An index of a large-scale Kuroshio Extension (KE) sea surface height dipole (KED) mode is constructed using satellite altimeter sea level anomaly observations from January 1993 to December 2015 based on previous work of the second author. It is found that the KED mode that undergoes a decadal variation from a negative phase (a positive-over-negative dipole, KED−) to a positive phase (a negative-over-positive dipole, KED+) can affect the variability of the oceanic SST front and the North Pacific storm track. The results show that the oceanic SST fronts in the north of the KE region and in the KE region — referred to as the NSST and KSST fronts, respectively — are closely correlated with the KED mode. In the NSST front region, the SST front is stronger for KED− than for KED+, and the opposite is the case in the KSST region. It is further revealed that the decadal phase transition of the KED mode can change the location and strength of the North Pacific storm track, with the North Pacific storm track being slightly weaker and moving more northwards as a whole during the KED− mode than during the KED+ mode. The westerly wind associated with the storm track on the downstream side of the KE region intensifies and shifts northwards under KED− compared to KED+. Furthermore, the transition of the KED mode gives rise to changes in the North Pacific storm track by changing the NSST and KSST fronts and meridional heat flux.
Highlights
IntroductionThe Kuroshio Extension (KE) is the eastward jet extension region where the western boundary current loses the support from the Japan coast (Mizuno and White 1983). Qiu and Chen (2005) noted by using sea surface height (SSH)
The Kuroshio Extension (KE) is the eastward jet extension region where the western boundary current loses the support from the Japan coast (Mizuno and White 1983). Qiu and Chen (2005) noted by using sea surface height (SSH)data that the KE system shows a clear decadal variability.It is recognized that the first and second modes of the empirical orthogonal function (EOF) — EOF1 and EOF2, respectively — reflect the annual and decadal variations of the KE system; EOF2 describes the variations of the southern recirculation gyre with a periodicity of 8–10 years
A negative center at 36°N (Figure 2(f)). This reflects that the oceanic SST front is stronger and located more north when the KED mode is in a negative phase
Summary
The Kuroshio Extension (KE) is the eastward jet extension region where the western boundary current loses the support from the Japan coast (Mizuno and White 1983). Qiu and Chen (2005) noted by using sea surface height (SSH). The SST front in the midlatitude zone can influence the location and strength of the Pacific storm track, especially its latitude (Chen, Plumb, and Lu 2010; Ma and Xu 2012; Ogawa et al 2012). It is meaningful to examine how the variation of the KED mode affects the SST front and subsequently the Pacific storm track, which is the purpose of the present paper
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