Dry Intrusion's Feature and Its Relationship with Rainfall Regions on Cold Vortex Heavy Rain Process in Northeast China

Based on the NCEP/NCAR 1°×1° reanalysis data, FY-2C satellite data and conventional meteorological observations, the characteristics of the dry intrusion and its impacts on the formation and development of the cold vortex heavy rain during 20- 24 July, 2006 are analyzed. The results show that the dry intrusion is a dark and obvious zone on the water vapor image. The dark zone has a better correspondence with the dynamic field corresponding with the distribution of the high potential vorticity at 350 hPa. Dry intrusion area is the overlap of both high potential vorticity and low humidity. Forefront of the dry intrusion is the rainfall regions, which indicates that the dry intrusion has a close relationship with strong rainfall regions. The downward cold air characterized by high potential vorticity and low humidity in the upper troposphere enhances the development of cold vortex heavy rain. The cold vortex heavy rain increases with an increasing intensity of dry intrusion. Meanwhile, the cold advection plays a very important role in variation of DII.