Diagnostic Analysis of a Heavy Rain Process in the Central of Hexi Corridor

For the process of the rainstorm occurred in central Hexi Corridor from 13: 00 29 to 03: 00 30 July 2012,based on the conventional aerological sounding and surface data,intensive regional rainfall data,FY- 2 satellite cloud imagery and NCEP reanalysis data at 1° × 1° spatial and 6 hours temporal resolution,the weather circulation pattern,the influence system,physical parameters characteristics,satellite cloud imagery and mesoscale system of the rainstorm before and later were analyzed by the synoptic diagnostic method. The results showed that the rainstorm occurred in the context of favorable large scale weather conditions. The flow field presented the pattern ofhigh in the east and low in the westin high and low layer of the sky,and the Balkhash Lake cold trough brought out the occurrence of the rainstorm. When the rainstorm happened,an intensive pumping action formed due to the upper layer divergence and lower layer convergence,at the point the strong ascending motion appeared in the troposphere,so the flow field pattern was favorable for the transport and gather of moisture. The 500 hPa vertical distribution of helicity was corresponding with the weather system and strong precipitation. The 700 hPa Qaidam warm vortex and the mesoscale weather system on ground provided dynamic conditions for unstable energy storage and the rainstorm,and the development of strong warm advection from Lanzhou to Hexi Corridor offered thermal conditions. Furthermore,the mesoscale and microscale weather systems were obvious during the period of the torrential rain.