北欧海大气低空辐合辐散的东西振荡模态及其相应的大气遥相关异常环流

The East-West Oscillation Mode of Nordic Seas Convergence Field and Its Associated Atmospheric Teleconnection Anomalous Circulation

北欧海作为连接北冰洋和北大西洋的重要海域,其由热效应产生的辐合场值得关注。本文利用NECP/NCAR的速度势函数(Velocity Potential,VP)数据表征北欧海辐合辐散场,发现在秋冬季北欧海上空大气低层存在一个独立的辐合区域。经验正交函数分解结果表明,北欧海上空的VP显示出除了表征北极涛动的全区一致型模态外,还表现出一个东西向辐合辐散反位相的东西振荡型模态。该模态与一支连接北大西洋涛动(NAO)和欧亚遥相关(EU)的复合型大气遥相关波列有关,北欧海表层潜热和感热异常加热通过影响低空大气的异常辐合辐散,与北大西洋偶极子型海温异常加热共同作用,加强了NAO异常环流;同时高空急流波导作用加强了从北欧海到东亚的EU波列,使得位于NAO和EU之间的北欧海成为连接NAO和EU大气遥相关波列的“中继站”,进而通过这种复合型大气遥相关波列将北大西洋与东亚大气环流联系起来,形成对东亚地区天气气候的远程影响。

As an important water connecting Arctic Ocean and North Atlantic,the Nordic Seas is of special concern for its heating effect and convergence/divergence filed.This paper uses the velocity potential(VP)data from NCEP/NCAR to represent the convergence filed over Nordic Seas.In October to December(OND)the climate state of VP shows an isolated convergence area over Nordic Seas.Except an area consist mode which represent the Arctic oscillation(AO)variation,an east-west oscillation mode is also found in the empirical orthogonal function result for Nordic Seas OND VP field.The east-west oscillation mode is related to a complex atmospheric teleconnection wave train connecting the North Atlantic Oscillation(NAO)and Eurasian teleconnection(EU).By effecting the low-level atmosphere convergence field,surface latent and sensible heating over Nordic Seas can consist with the heating by North Atlantic SST dipole anomaly,together strengthen the NAO anomaly circulation.At the same time,the high-altitude jet stream waveguide effect strengthen the wave train from Nordic Seas to East Asia,making Nordic Seas becomes the"relay station"which connecting the NAO and EU atmospheric teleconnection wave train,and then connects the north Atlantic with the east Asian atmospheric circulation through this composite atmospheric teleconnection wave train,forming the remote influence on the weather and climate in East Asia.