夏季东亚高空急流与天气尺度波动的气候特征之间的联系

利用NCEP/NCAR逐日资料(1979~2003年),分析了东亚夏季高空急流和天气尺度波动气候特征之间的联系。通过分析急流与天气尺度波动活动量Q(用于描述某一时间段内天气尺度波动活动强弱程度)、热量涡动输送(V′T′)的关系,发现:在气候平均意义下,天气尺度波动活动量在6、8月较大,这意味着在这两个月中,天气尺度波动较为剧烈。这和急流的强度变化是相对应的,即强的天气尺度波动活动量对应着强的急流,弱的天气尺度波动活动量对应着弱的急流。热量涡动输送也表现出与天气尺度波动活动量类似的特征。年际变化上,夏季平均和6、7、8各月平均的热量涡动输送和急流强度都存在显著的正相关。对强、弱急流年份条件下热量涡动输送合成分析的结果表明:热量涡动输送偏南时,对应着强的急流;热量涡动输送偏北时,对应着弱的急流。以上的研究结果说明,在气候平均意义和年际变化上夏季东亚高空急流和天气尺度波动之间有着密切的联系。

The Relationship between the East Asian Up-tropopheric Jet Stream in Summer and Climatic Characteristics of Synoptic-scale Disturbance

Using the NCEP/NCAR daily data(1979-2003),the relationship between the East Asian up-tropospheric jet stream in summer and climatic characteristics of synoptic-scale disturbance is analyzed.We examined the relationship between the jet stream and activity of synoptic-scale disturbance Q,which depicts intensity of synoptic-scale disturbance in a period of time,and the relationship between the jet stream and transient eddy heat flux.The results show that in the climatological sense,activity of synoptic-scale disturbance is much stronger in June and August,which is corresponding with the variation of jet stream.Stronger activity of synoptic-scale disturbance is associated with stronger jet stream,and vice versa.The transient eddy heat flux show similar features of activity of synoptic-scale disturbance.On the interannual time scale,there exists significant positive correlation between the transient heat flux and the strength of jet stream in summer(JJA mean),June,July,August,respectively.Composite analysis shows that corresponding to southward displacement of transient eddy heat flux,the strength of jet stream is stronger and vice versa.All results show that climatologically and on the interannual time scale,the East Asian up-tropopheric jet stream in summer and climatic characteristics of synoptic-scale disturbance are closely connected.