东北冷涡的结构及其演变特征的个例综合分析

A comprehensive analysis of the structure of a northeast China-old-ortex and its characteristics of evolution

中文关键词:  东北冷涡， 三维结构， 干侵入， 等熵气流

英文关键词:Northeast China-cold-vortex, Thermodynamic structure, Dry intrusion, Isentropic currents

中文摘要:

      利用NCEP再分析资料、FY-2C、CloudSat云探测卫星和实况观测等资料对2009年6月27—30日出现的东北冷涡的热力动力结构、三维流场和云系演变特征进行了分析，并初步探讨了冷涡的发生、发展机理。结果表明：该冷涡冷心结构最初始于高层，随后逐渐向下伸展。成熟阶段的冷涡，对流层整层为冷心结构，冷中心位于对流层中高层，其上即平流层低层为暖心结构，中心东西两侧上升气流随高度向外倾斜，经向风趋于对称。发展初期温度槽落后于高度槽，且轴线向西倾斜，斜压性特征明显；至成熟阶段，温度中心与高度中心趋于重合，轴线近于竖直，显示出正压的特征；到减弱阶段，由于低层偏北风减弱明显，轴线又略向西倾斜。冷涡云带的产生与低层辐合带密切相关。CloudSat云探测卫星资料分析结果表明，冷涡环流内多中小尺度对流云团发展，且分布极不均匀。此次个例的研究结果揭示出冷涡的形成和发展跟对流层中上层切断低压的生成发展与对应的地面低压逐步耦合的动力学过程紧密相关，其中，冷暖气流呈旋转式下沉和上升，在冷涡中心形成偶极；对流层高层的干冷空气总是沿着等熵面从高层穿越等压面向下侵入到冷涡中心附近，干侵入使冷涡加强发展并维持其冷心结构。干侵入机制实际就是高位涡的侵入和下传，对预报冷涡的发展演变具有重要指示意义。

英文摘要:

      The thermodynamic and dynamic structure of a northeast China-cold-vortex and its changes in the associated three-dimensional currents and cloud-series characteristics are analyzed using the NCAR/NCEP reanalysis data, the data from FY2C and CloudSat as well as the conventional observations, and a preliminary investigation into the possible mechanism responsible for the genesis and development of the vortex is addressed in this paper. The results show that the cold core structure of the cold vortex is initiated at the higher levels and then extended downwards. The cold vortex at its mature stage shows a cold-core structure throughout the troposphere with the cold centre located in the mid-higher troposphere above which (i.e. in the lower stratosphere) there exists a warm core structure. On both the eastern and western sides of the centre the updrafts tilt to the outside with height with the longitudinal winds tending to symmetrize. At the initial stage the temperature trough lags behind the height trough with its axis tilting toward the west, showing a strong baroclinity. During its maturity the temperature centre tends to coincide with the height centre with the axis tending to be vertical. The axis line tilts toward the west again at the stage of decay owing to a distinct reduction of the northerly in the lower levels. The generation of the cloud bands associated with the cold vortex is substantially caused by the low level convergence zone. The analytic results based on the data from the satellite CloudSat show that there are a lot of the convective cloud clusters of heterogeneous pattern developed within the cold vortex circulation. The genesis and development of the cold vortex are closely related with the dynamics of the formation and the intensification of the cut-off low in the mid-upper troposphere and of the gradual coupling with the corresponding depression at the surface. It is found that a dipole forms arou