Impacts of mesoscale sea surface temperature anomalies on the meridional shift of North Pacific storm track

Abstract

In this study, an index for the variability of mesoscale sea surface temperature (SST) anomalies over the Kuroshio and Oyashio confluence region (KOCR) is proposed based on the high-resolution SST data set. The positive phase of the new index indicates that the mesoscale SST anomalies are strong and feature double peaks of variance within the KOCR, and the negative phase of the index denotes weak mesoscale SST anomalies and a broader single peak of variance. Composite analysis is conducted on the relation between the variability of mesoscale SST and the North Pacific storm track. The mechanism behind the relation is then investigated. We find that the storm track is shifted southwards (northwards) during the positive (negative) phase of the index. The variability of mesoscale SST impacts first the turbulent heat fluxes out of the ocean, changing the near-surface baroclinicity with the large-scale zonal wind. The baroclinic energy conversion resembles the baroclinicity anomaly, modulating the anomaly of the storm track along the southern side of its climatological peak.