一次初春东北冷涡的结构特征及其降水成因

利用ERA-Interim逐日再分析资料及中国753站逐日降水资料，对2008年3月23—28日的东北冷涡天气过程进行诊断分析，并探讨了冷涡降水的主要影响因子。结果表明：1）与夏季冷涡过程不同，此次初春冷涡过程高层环流场由经向环流向纬向环流转变；冷涡发展初期，经向环流的建立使得冷涡向南移动，而成熟阶段冷涡后部的低槽引导冷空气向冷涡输送，导致了冷涡环流的维持。2）亚欧大陆上空强阻塞形势的发展是初春东北冷涡形成的关键因子；乌拉尔山和鄂霍次克海阻塞高压分别受到前期北大西洋和热带太平洋海温异常的调控，为冷涡向南发展维持提供了有利的环流背景，并影响了高低空急流的配置，有利于冷涡降水的形成。3）涡度场和温度场的高低空配置使得东北冷涡发展成深厚的环流系统，干侵入对冷涡的形成和维持同样有重要作用。冷涡环流的发展为东北地区降水提供了有利的水汽和垂直运动条件，冷暖平流交汇引起的锋面过程则促进大范围降水的形成。

Analysis on the structural characteristics of an early spring cold vortex event in northeastern China and the formation mechanism of vortex precipitation

In this study, based on the daily ERA-Interim reanalysis data and daily precipitation data from 753 stations throughout China, the synoptic process of the northeast cold vortex during the period of March 23-28, 2008 was analyzed.In addition, the main factors influencing the cold vortex precipitation were also discussed.The results showed that, unlike the summer cold vortex, the upper-level circulation of the early spring cold vortex event underwent a transition from meridional circulation to zonal circulation.The establishment of the meridional circulation during the early stage guided the cold vortex to move southward, while the low trough to the rear (west) of the cold vortex supplied cold air for the development and maintenance of the cold vortex circulation.The blocking systems over the Eurasian continent were key factors influencing the early spring cold vortex.The Okhotsk Sea blocking high and Ural blocking high were respectively regulated by the tropical Pacific and preceding North Atlantic Sea surface temperature anomalies, which provided a beneficial background for the southward development and maintenance of the cold vortex.The jets at the lower and upper levels were also modulated by the Okhotsk blocking high, which was conducive to the formation of cold vortex precipitation.The configurations of the vorticity field and temperature field caused the cold vortex to develop into a deep circulation system, while the dry-air invasion also played an important role.The development of cold vortex circulation provided favorable vertical motion and water vapor conditions for precipitation in northeastern China.Finally, the frontal process induced by the cold and warm advection promoted the formation of large-scale precipitation.