Based on conventional observations, data from regional automatic weather stations, Doppler weather radar data, satellite cloud images, ground based GPS/PWV data, monitoring data from lightning location instrument and NCEP/NCAR reanalysis with 1°×1° resolution, we have conducted an analysis of circulation environment and mesoscale convective feature of an excessive heavy rain event in northern Henan on 9 July 2016. The results show that it occurred under the circulation environment of the No.1601 typhoon moving northwards, the 500 hPa low vortex slowly moving eastwards and the 200 hPa jet stream stabilizing and continuing. Convergence in the low-level and divergence in the upper level, and positive and negative temperature advections in boundary layer are symmetrical distributions, which are corresponding to secondary circulations and make ascending motion strengthened. Severe convective unstable atmospheric stratification supplies a beneficial thermodynamic condition for the occurrence of severe precipitation. High value centers of water vapor flux and vapor convergence are coincident to the center of heavy rain in northern Henan. The GPS precipitable water vapor (GPS/PWV) increases rapidly before severe precipitation begins, and the severe precipitation weakens or stops when the PWV decreases rapidly. The severe precipitation is mainly
caused by mesoscale convective cloud clusters, which are continuously generated and developed among the low vortex cloud systems, corresponding to the area of big values of Temperature of Brightness Blackbody (TBB) gradient and being closed to the center of low values of TBB. At the same time, the peak value of cloud-to-ground lightening frequency appears 1-3 h ahead of the peak value of severe precipitation. The warm and wet areas in ground level and the intrusion of the θse cold tongue play an important role in the formation of mesoscale convection. The surface convergence line that triggered mesoscale convection systems and maintained for a long time causes the development of heavy rain in northern Henan. Blend echoes are characterized by the typical train effect. Strong echo extends less than 3 km high whose centroid height is low, being different from the echo structure of hailstorm but similar to the tropical marine precipitation echo. It can be found in the radar velocity charts that counter-wind zones and convergent zones emerge frequently. The special terrain in northern Henan forms a channel for the cold air moving southwards. The southeast airflow keeps in the low-level, whose wind direction is perpendicular to the orientation of mountains. Topographic forcing effect and convergence effect from friction result in an increase in rainstorm.