1998年夏季东北亚阻塞高压异常的大尺度环流特征及成因初探

分析了1998年夏季东北阻塞高压异常及大尺度环流特征，研究了1979－1998年夏季东北阻塞高压年际变化，环流背景特征以及东北亚阻塞高压异常的太平洋海温异常的关系，认为夏季东北亚500hPa平均高度偏高（低），东亚地区“＋－＋”（“－＋－”）的距平波列，是典型的东北亚阻塞高压强盛（稀少）的环流型，太平洋海温的异常，激发东焉地区的遥相关波列，致使东北亚500hPa高度场异常，可能是东北亚阻塞主压异常的原因之一，在亚少中高续高度场平均偏高的环流背景下，乌拉尔册地区的阻塞高压对东北亚阻塞高压的发展和建立起到了促进作用，1998年乌拉尔山阻塞高频繁也是东北亚阻塞高压异常频繁的可能原因之一。

LARGE SCALE CIRCULATION FEATURES AND REASONS CAUSING BLOCKING HIGH ANOMALY OVER NE ASIA IN SUMMER OF 1998

The anomaly of the blocking high over the North-east Asia and the lager scale circulation feature in summer of 1998 are analyzed.The interannual changes of blocking high over the NE Asia, the circulation background and the relationship between the anomaly of blocking high over the NE Asia and SSTA over the Pacific Ocean in summer of 1979～1998 are studied. The results indicate that the “+-+” pattern of 500　hPa geopotential height anomaly from high to low latitude is the typical when blocking days are more than normal over the NE Asia,and v.v.The SSTA over the Pacific Ocean causes the teleconnection wave train and the 500　hPa geopotential height anomaly over mid-high latitude over the East Asia.It might be one of reasons leading to the blocking high anomaly over the NE Asia.Under the circulation background of the higher geopotential height over the mid-high latitude, the blocking high over the area of Ural promotes the establishment and development of the blocking high over the NE Asia.The blocking high over the area of Ural happening more frequently than the normal may be one reason of the more blocking high over the NE Asia in summer of 1998.