Eddies during the Blocking Maintenance over the Northeastern Asia in Summer
夏季东北亚阻塞形势维持时的天气尺度波

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.