阻塞流场与瞬变涡动相互作用的动力学研究  

A Dynamic Study of the Interaction between Transient Eddies and Blocking

作　　者：刁一娜[1] 李建平[2] 罗德海[1] 

机构地区：[1]中国海洋大学海洋环境学院,青岛266003 [2]中国科学院大气物理研究所大气科学与地球流体力学数值模拟国家重点实验室,北京100029

出　　处：《大气科学》2004年第6期901-924,共24页Chinese Journal of Atmospheric Sciences

基　　金：国家自然科学基金资助项目 40 1 70 1 93; 40 2 75 0 2 5和 40 3 2 5 0 1 6共同资助

摘　　要：借助于一个 β通道正压模型 ,模拟了瞬变天气尺度扰动与大尺度阻塞流场相互作用 ,以及所形成的“Ω”型阻塞对风暴轴地带瞬变扰动涡列移动路径的影响 ,并用描述局地能量变化率的方程分析了能量收支情况的细致结构。结果表明 ,瞬变扰动在其与背景流场的相互作用过程中 ,在阻塞发展阶段 ,阻塞受到瞬变扰动涡的涡度和能量强迫 ,背景流场增强发展成为阻塞系统。对两种不同的阻塞流场背景下瞬变扰动能量变化的分析表明 :在阻塞区扰动瞬变涡失去能量 ,在南北边缘瞬变扰动的能量变化趋势表现为沿着阻塞外围向下游传播的特征并从背景流场得到能量 ,从而瞬变涡动由源区的一列分裂为绕行于阻塞外围的两列。在两种不同背景阻塞流场结构下瞬变涡动的移动路径表现出不同的分布特征 :当偶极子型阻塞作为背景流场时 ,瞬变涡动的移动路径呈南北对称分布于阻塞区的外缘 ;当瞬变涡的背景流场为“Ω”型阻塞时 ,瞬变扰动带受到“Ω”型阻塞流场结构的影响 ,表现出北支强南支弱的特征。这些结果与实际观测一致。Using a β channel barotropic model, the paper discusses the interaction between the transient synoptic-scale eddies and the blocking, and investigates the role played by the “Ω”type blocking in offecting the moving trace of the storm track. An equation describing the changing rate of the local energy is applied to analysing the details of the energy budget of the transient eddies when they interact with the blocking flow. The results show that the initial weak planetary scale ridge can develop into a strong and steady blocking flow under the energy and the vorticity forcing of the synoptic eddies coming from upstream. The energy budget analysis of the synoptic eddies shows that in the blocking area the synoptic eddies lose energy while in the northern and southern vicinity of the blocking area eddies gain energy and move downstream along the northern and southern edges of the blocking area. Thus the upstream eddies are transformed from one train into two trains under the feedback of the blocking flow. Interacting with two different types of the blocking flow is considered in this paper, the transient synoptic eddies show the different traveling traces: when the background planetary scale the blocking flow is a dipole type, the trace of the eddies distribute symmetrically along the southern and northern edges of the blocking area; when the blocking flow is the “Ω” type, the traveling eddies show an asymmetric trace, viz the northern train is strong and the southern one is very weak. The results are consistent with the phenomenon showed by the observational data that the winter storm track is always deflecting northward.

关 键 词：移动路径 天气尺度 正压模 涡度 源区 扰动 风暴 涡动 流场 相互作用 

分 类 号：P458[天文地球—大气科学及气象学] O347.6[理学—固体力学]