夏季东亚高空急流与太平洋-日本遥相关型的关系

利用NCEP/NCAR和NOAA月平均资料,采用奇异值分解方法分析了夏季东亚高空纬向风场和西北太平洋海表温度(SST)的耦合关系,并据此研究了东亚副热带高空急流和太平洋-日本(Pacific-Japan,PJ)遥相关型的可能联系。合成分析结果表明,东亚副热带高空急流正模态年,急流偏南偏强,对流层上层南亚高压增强东进,中层西太平洋副热带高压加强西伸,菲律宾周边海域SST升高,中纬度黑潮延伸体区SST降低,菲律宾海和热带西太平洋地区对流活动偏弱,日本海和黑潮延伸体海区对流活动增强,对应PJ遥相关型的负位相;而东亚副热带高空急流负模态年,急流偏北偏弱,对流层上层南亚高压减弱西退,中层西太平洋副热带高压减弱东撤,菲律宾周边SST降低,中纬度黑潮延伸体区SST升高,菲律宾海和热带西太平洋地区对流活动强盛,日本海和黑潮延伸体海区对流活动减弱,对应PJ遥相关型的正位相。由于夏季东亚副热带高空急流活动与PJ遥相关型存在关联,PJ遥相关型可能是东亚副热带高空急流响应太平洋海温异常的纽带。

The relationship of summertime upper level jet over East Asia and the Pacific-Japan teleconnection

The singular value decomposition (SVD) method is applied in this study to investigate the coupled mode between summertime upper-level zonal winds over East Asia and sea surface temperatures (SSTs) in the WesternNorth Pacific. Monthly means of wind fields, geopotential height, and vetical velocity from NCEP/NCAR reanalysis and SSTs from NOAA observations are used in this study. Possible relations between the upper-level jet stream over subtropical East Asia and the Pacific-Japan (PJ) teleconnection are explored. Results indicate that in the years of positive mode for the East Asian subtropical jet (EASJ), the EASJ intensified and shifted southward; the South Asian High in the upper troposphere intensified and extended eastward; the western Pacific subtropical high (WPSH) strengthened and extended westward in the mid-troposphere; SST warming occurred over the Philippine Sea while SST cooling was found in the Kuroshio Extension region; convective activities weakened over the Philippine Sea and the tropical western Pacific but intensified over the Japanese Sea and the Kuroshio Extension region in the mid-latitude. The positive mode years for the EASJ correspond to negative PJ phase. In the years of negative EASJ mode, the EASJ shifted northward and weakened; the South Asian High in the upper troposphere weakened and retreated westward; the WPSH in the mid-troposphere weakened and withdrew eastward; SST cooling was found over the Philippine Sea while SST warming occurred over the Kuroshio Extension region in the mid-latitude; convective activities intensified over the Philippine Sea and the tropical western Pacific but weakened over the Japanese Sea and the Kuroshio Extension region. The negative EASJ mode years correspond to positive PJ phase. Since the summertime upper-level jet stream activities over subtropical East Asia are closely related to the PJ teleconnection, it is possible that the PJ teleconnection behaves as a linkage between the EASJ activities and SST anomalies in the western North Pacific.