Numerical Simulation And Diagnostic Analysis Of The Rainstorm Process In North China Occurred On August 16 2005

By employing the observational data froms MICAPS system, NCEP reanalysis dataand the lh rainfall of the automatic meteorological observing station, a heavyrainstorm happened in North China during the period from 0000 UTC 16 August to 0000UTC 17 August 2005 is diagnozed. The analyses show that the upper trough subtropicalhigh are the macro-scale impact system. The shear line, the conflict of warm and coldmass and low is the influence system. At the same time, the plentiful water vapor andunstable are favor for the form and maintenance of rainfall.The composite reflectivity and base velocity of radar show that the MCS bringabout the heavy rain, and the development of strong echo and anti-wind area reflectthe change of the rainfall area and rainfall density.The mesoscale numerical model MM5 is used to simulate the rainstormprocess, and the output is reasonable. We use the output of the model to analyzethe mechanism of this rainfall, and we find that dry intrusion had importantimpaction on the rainstorm. The dry air in the upper troposphere intruded into thelower layer make the surface temperature and surface pressure change, and theconvergence enhanced. Moreover dry intrusion was propitious to the development andenhancement of the cyclone.