夏季东北亚阻塞形势维持时的天气尺度波

利用NCEP/NCAR逐日资料，分析了一次夏季东北亚阻塞形势维持期间(1991年6月27日至7月16日)高频波活动强弱的分布和传播的特征，发现在阻塞高压上 游的巴伦支海上空有明显异常的高频波活跃区，从该活跃区和位于东北大西洋的常年活跃区，高频波不断东传，传到东北亚时，变弱消亡。据此，作者推测高频波的能量传给了阻塞形势，使阻塞形势得以维持。利用Eu矢量分析的高频波能量传播也表明了这一点。此外，利用Eu和Ev矢量讨论了高频波对纬向平均流和经向平均流的反馈强迫作用。结果表明，高频波的强迫作用使得时间平均纬向流在急流分支处呈减弱的趋势。高频波对时间平均的经向流反馈强迫作用更加明显，这种强迫使得急流在阻塞高压的上游产生分支，而在下游产生南北分支气流的汇合。最后，分析了高频波和低频波对热量的南北输送，表明在阻塞期间高频波在东亚地区对流层顶附近产生非常清楚的向北热量输送(冷空气向南输送或暖空气向北输送)，而低频波(可用来表示阻塞流型)的向北热量输送作用表现在对流层中下层，相对来讲不明显。

Eddies during the Blocking Maintenance over the Northeastern Asia in Summer

Using the NCEP/ NCAR daily data, the intensity and propagation of band-pass eddies (2.5 to 6 days) during a blocking episode over the northeastern Asia in summer (from June 27 to July 16, 1999) are examined. The analyzed results show that the intensity of band-pass eddies are stronger considerably than climatology over the upstream of the blocking high (or over the Barents Sea). The band-pass eddies continually propagate eastward from the Barents Sea and a climatological storm track region of the Northeast Atlantic, and decayed sharply over the northeastern Asia. It is inferred that eddies transfer their energy to the blocking high over the northeastern Asia during the blocking maintenance. The analysis by use of vector Eu also confirms such an energy propagation of the band-pass eddies. The forcing role of the band-pass eddies on the time-mean zonal and meridional flows is also examined by use of vectors Eu and Ev. It is shown that the forcing of band-pass eddies is acting to decelerate the time-mean westorlies around the splitting point. The forcing of band-pass eddies, in addition, clearly results in the splitting and confluence of the mean flows at the up- and down-stream regions of the blocking high, respectively. Finally, the meridional heat transport by highand low-frequency components is analyzed. The analyzed result clearly shows that the heat is fluxed northward (i.e., southward transport of colder air or northward transport of warmer air) by high- frequency component around the tropopause over East Asia. The transport by low-frequency component (that can be referred as the role of blocking flow pattern), however, appears in the middle and lower troposphere, and is relatively obscure.