Mesoscale features and dynamic mechanisms of torrential rain in Heilongjiang province

Mesoscale features and dynamic mechanisms of the heavy rainfall happened on July 20-21,2014 are analyzed with the micaps conventional observations,automatic ground station data. The results show that: the heavy rainfall was caused by the vortex, subtropical high, and Meng-Gu cyclone, warm front triggered the storm;the southwest low-level jet brought abundant vapor and instability energy for the rainstorm, at the same time, the hollow jet with dry tongue convey cold air, the combination strengthened the instability of the atmosphere, frontogenesis triggered the convectional weather;merging and strengthening of the mesoscale convective cloud cluster in the rainstorm is the main reason of the rainstorm process. Rain intensity was significantly enhanced with the development of cloud. Bohai bay is the main water vapor source of rainstorms, in the low level, intense water-vapor transfer and convergence made the humidity level increased rapidly which provide the rainstorm water vapor to develop.The whole positive vorticity area is conductive to generate cyclonic convergence upward motion and it provide ample power storm conditions. K index, convection effective potentials and fake a considerable potential temperature all indicate the possibility of strong convective weather.