前秋墨西哥湾流延伸区海温与东亚冬季风关系的年代际变化

Decadal variation of relationship between sea surface temperature of autumn gulf stream extension and the East Asian winter monsoon

利用NCEP/NCAR再分析资料、哈德莱环流中心海表温度资料,研究了墨西哥湾流延伸区海温与东亚冬季风关系的年代际变化及可能原因。结果表明,秋季纽芬兰东南侧的墨西哥湾流延伸区海温与东亚冬季风联系在1970s中后期发生明显年代际突变,由1948—1976(P1)显著正相关变为1980—2012(P2)时段的不显著负相关。同时,与湾延区海温相联系的环流系统在P1和P2时段改变明显:P1时段湾延区海温偏高,冬季500 hPa位势高度场乌拉尔以东地区为大范围显著正异常,日本上空东亚大槽加深,东亚沿岸产生显著偏北风;而P2时段湾延区海温偏高,贝加尔湖上空为不显著负异常位势高度,东亚大槽区为弱的正异常,东亚沿岸有不显著偏南风异常。造成该突变的可能原因是P1时段湾延区海温偏高容易激发出北大西洋到东亚"正、负、正、负"的异常波列,且该异常中心与正位相欧亚遥相关(EU)波列的异常中心位置基本一致,位相叠加加强了正EU,进而造成东亚冬季风的异常强劲。而P2阶段从西欧到东亚沿岸呈现不显著的类似负位相EU波列,且异常中心与EU波列的异常中心位置有偏差,导致其与东亚冬季风关系相对于P1阶段发生了由显著正相关到不显著负相关的转变。

By using NCEP/NCAR reanalysis dataset and Hadley SST dataset,the decadal variation and possible reasons of the relationship between the Sea Surface Temperature( SST) of Mexico Gulf Stream extension area and East Asian Winter Monsoon( EAWM) were analyzed.Results indicate that the relationship between the Mexico Gulf Stream extension area located in the Southeast Newfoundland and EAWM variability had obvious decadal variation in the 1970 s,and the correlation statistically changed from significantly positive one during 1948-1976( P1) to weakly negative one during 1980-2012( P2).Meanwhile,the circulation system related to SST in Gulf Stream extension area changed obviously during p1 and P2.During P1,when the Sea Surface Temperature Anomaly( SSTA) is significant positive in autumn,the anomalies of winter geopotential height at 500 hPa is significant positive over East Urals,the East Asian trough over Japan deepens and significant north wind occurrs over coastal East Asian.But for the P2,the anomaly geopotential height over Baikal is weakly negative while the anomaly of East Asian trough region is weakly positive.Therefore,East Asian prevails insignificant south wind anomalies.Further study suggests that during P1,the positive SST anomaly of Gulf Stream extension area easily triggered ‘+,-,+,-'anomalous wave-train structure from Northeast Atlantic to East Asian,and the in-phase superimposition of the anomalous wave-train was consistent with Eurasian( EU) teleconnection pattern,resulting in a strong EAWM.However,during P2,the weakly negative EU-like pattern aroused and the centers of action related with SST anomaly of Gulf Stream extension have location deviations compared with traditional EU pattern.Therefore,opposite to P1,the connection between the SST anomaly of Gulf Stream extension and EAWM is quite weak during P2.