Strengthened connection between meridional location of winter polar front jet and surface air temperature since the mid-1990s

Abstract

This study reveals a marked enhancement in the relationship between the variations in location of the winter East Asian Polar Front Jet (EAPJ) and the surface air temperature (SAT) in Eurasia since the mid-1990s. Before the mid-1990s, an evident wave train related to the meridional location of the EAPJ exhibited an anticyclonic anomaly over northern Europe and a cyclonic anomaly in northwestern Asia. With an equatorward shift of the EAPJ after the mid-1990s, the wave train experiences a notable adjustment that is conducive to East Asian cooling, displaying an anticyclonic anomaly around the Kara-Laptev Seas and a cyclonic anomaly near northeastern Asia. Arctic warming anomalies and sea ice loss contributed significantly to these decadal changes. Simulation experiments forced by observed Arctic sea-ice variability further confirm this result. Since the mid-1990s, Arctic sea ice loss (or Arctic warming anomaly) has contributed to a reduction in westerly winds in high latitudes by modulating the meridional temperature gradient. The deaccelerated winds intensify the Arctic cold air propagating to the south, enhancing the atmospheric baroclinicity and the westerly flow in the upper level at the south side of the EAPJ, favoring the southward shift of the EAPJ. With the equatorward shift of the EAPJ, the corresponding SAT anomalies in East Asia are more salient.