TRANSIENT EDDY TRANSFER AND FORMATION OF BLOCKING HICH──ON THE PERSISTENTLY ABNORMAL WEATHER IN THE SUMMER OF 1980

In the summer of 1980, serious persistently abnormal weather occurred over vast areas in China. The long-lasting of such disasterous weather is mainly due to the stable development and maintenance of blocking anticyclone over the northeastern Asia. This study aims at the understanding of the roles of transient eddy transfer in the formation of the blocking.It was shown that during this period. there appeared continuous generation of synopticscale perturbations along the strong baroclinic zone over Europe and western Asia. While such perturbations propagated eastward, energy conversion occurred. At equivalent barotropic layer with weak dissipation, such energy conversion subjects to the so-called bidirectional principle: while the energy of the synoptic-scale system is cascaded to smaller scale system, a much larger portion is transferred to the blocking system with larger scale. Potential vorticity diagnoses also reveal that transient weather systems play the roles of maintaining the mean anticyclonic vorticity to the south. and mean cyclonic vorticity to the north, of the westerly jet, and exciting strong anticyclonic vorticity growth and corresponding altitude increase in the high latitude area located downstream of the westerly diffluence region. The research also shows that, the intensity of the forcing of blocking formation via wave-mean flow interaction in this Asian case is much stronger than that in western Europe occurred in the summer of 1976. It was therefore concluded that when persistently abnormal weather in the northern China is studied. in addition to the subtropical weather systems, attention should also be drawn to the development of baroclinic zone over Europe and western Asia,and the propagation and transfer properties of synoptic systems embedded in the baroclinic zone.