A case study on conditions forming stratiform mixed-phase clouds in northeast cold vortex

Based on reanalysis data from NCEP/NCAR center on July 7-8, 2003 and the sounding data from ground and deep space, the conditions forming stratiform mixed-phase clouds in northeast cold vortex were analyzed. The results indicate that cold vortex weather consists of two low pressure systems in the north and south of northeast China. Both are deep and are accompanied with obvious low temperature zones. Precipitation in northeast China is mainly influenced by the south low pressure system. This system has cyclone circulation, and there exists humidity areas (relative humidity is more than 80%) in the center of cyclone, in the convergence area of airflow and in the southwest airflow of the southeast side of cyclone. Stratiform mixed-phase clouds could be formed in humidity area that relative humidity is more than 90%. Precipitation area is coincident with system’ instable area and energy convergence area. It suggests that stratiform mixed-phase clouds in northeast cold vortex are formed in the southwest airflow of the southeast cold vortex, in where transport conditions of water vapor are good, and it has high and humid instable areas. The above mentioned has the indicative significance to formation and development of mixed-phase clouds.