关键词: 关键词：东北冷涡, MCC, MCS, 辐合线, 对流不稳定

Abstract: Based on the meteorological conventional observation data, observational precipitation from automatic  weather stations and NCEP reanalysis data, the causes and mesoscale characteristics of the heavy rain occurring on July 16, 2019 in Heilongjiang Province under the background of northeast cold vortex were analyzed. The results show that there were two rainstorm areas in the western and eastern Heilongjiang Province affected by MCS and MCC activities, respectively. Both MCS and MCC clouds generated in Inner Mongolia and moved to Heilongjiang Province. Due to the enhanced convective instability and frontal generation, the MCC and MCS clouds developed, strengthened and moved from west to east along the convergence line. In the upper troposphere over the bottom of the cold vortex during the precipitation, there existed a dry intruding airflow with high momentum from the high latitude area. During the process of heavy rain caused by MCC, it presented strong convection instability in the lower atmosphere and moisture symmetry instability in the middle layer. The uplift of ground convergence line and frontal formation promoted the release of unstable energy. MCC was shown as a wide range of mixed cloud precipitation echo on the radar reflectivity products images. One of them was a supercell with hook echo structure, deep cyclone convergence and mesocyclone in middle and lower layers. Compared with MCS, the environmental field of MCC developing had greater vorticity in the middle and lower layers and stronger divergence in the upper layers. The upper levels had stronger pumping action, leading to a stronger upward movement. During the development of MCC, the environmental wind in the middle and lower levels increased significantly. There was greater vertical shear of horizontal wind resulting in stronger organization of mesoscale convective clouds.

Key words: Key words: northeast cold vortex, mesoscale convective complexes, mesoscale convective system, convergence line, convective instability