Responses of the East Asian Jet Stream to the North Pacific Subtropical Front in Spring
【摘要】：This study concerns atmospheric responses to the North Pacific Subtropical Front(NPSTF) in the boreal spring over the period of 1982-2014. Statistical results show that a strong NPSTF in spring can significantly enhance the East Asian jet stream(EAJS). Both transient eddy activity and atmospheric heat source play important roles in this process. The enhanced atmospheric temperature gradient due to a strong NPSTF increases atmospheric baroclinicity, resulting in an intensification of transient eddy activities and convection activities. On one hand, the enhanced transient eddy activities can excite an anomalous cyclonic circulation with a quasi-baraotropical structure in the troposphere to the north of the NPSTF. Accordingly, the related westerly wind anomalies around 30 oN can intensify the component of EAJS over the Northeast Pacific. On the other hand, an enhanced atmospheric heat source over the NPSTF, which is related to increased rainfall, acts to excite an anomalous cyclonic circulation in the troposphere to the northwest of the NPSTF, which can explain the enhanced component of EAJS over the Northwest Pacific. The two mechanisms may supplement each other to enhance the EAJS.