北太平洋上一个爆发性气旋族的结构分析

Analyses of a Family of Explosive Eyclones over the Northern Pacific

利用NCEP(National Centers for Environmental Prediction)再分析格点资料和HYSPLIT(Hybrid Single Particle Lagrangian Integrated Trajectory Model)模式对2012年1月1—10日发生在北太平洋的一个爆发性气旋族进行了研究,并对气旋族的两个主要成员Parent Low(气旋A)和Child Low(气旋B)的演变过程和时空结构进行了详细分析,发现在气旋A和气旋B的爆发性发展阶段,200hPa高空的辐散区向气旋输送正涡度平流,气旋处于500hPa大槽前部,系统轴线西倾,低层有强冷平流向气旋中心输送并与锋面结合,温度梯度较大。气旋西侧较强北风携带的冷空气与冷锋前来的暖湿空气相遇,为气旋的发展提供有利条件。从形势场上看,气旋B爆发性发展主要是依靠气旋A所提供的环流背景场。气旋A在高空为气旋B提供正涡度平流,在低空通过环流将冷平流输送到气旋B内部,使气旋B低层斜压性增加。在气旋A和气旋B的向东移动和"互旋"过程中,两者之间水汽输送通道逐步建立。东移过程中,气旋A不断向气旋B进行水汽输运,使得气旋B系统内部水汽含量增加,为气旋的发展提供能量。利用后向追踪法对气旋B中心附近的空气进行追踪发现,在1 000m以下,来自气旋A的空气占到总数的一半以上,可以认为气旋A是气旋B低层水汽来源的主要途径之一。

By using grid data provided by NCEP（National Centers for Environmental Prediction）and the HYSPLIT（Hybrid Single Particle Lagrangian Integrated Trajectory Model）model,we investigated a family of explosive cyclones occurred over the Northern Pacific from 1to 10 January,2012.Also detailed analyses are performed on the evolutionary process and the spatial-temporal structure of two major members（cyclones A and B）of this family of explosive cyclones.During the rapid developing stages of cyclones A and B,they were located beneath the 200 hPa divergence area receiving positive vorticity advection.They are in front of the 500 hPa trough.As the trough axis tilted westward,and with the lowlevel cold advection moving towards the central area of the cyclones combing with the fronts,the cyclones may be promoted to rapid development.In the western side of the cyclone,northerly wind conveyed the cold air from the continent meets with the warm air coming from the southerly wind in front of the cold front,providing the favorable condition for cyclogenesis.The circulation field provided by cyclone A played a significant role for the development of cyclone B.Affected by cyclone A,there is a strong positive vorticity advection in the 200 hPa divergence area where cyclone B located.Also due to the impact of circulation of cyclone A on lower atmosphere,dry-cold air was conveyed continuously into cyclone B,increasing the low-level atmospheric baroclinicity around cyclone B.During their eastward moving processes of cyclones A and B with twisting moving paths,we found that a moisture transport channel between them had been gradually established.During that process,the continuous moisture transport from cyclone A to cyclone B caused the moisture increasing for cyclone B.With the help of backward trajectory simulation,it is found that below 1 000 m,more than half of the total air around the center of cyclone B came from cyclone A.Thus,it supplied some reasons to believe that cyclone A was the main approach for the lower-level moisture transport of cyclone B.