A Diagnostic Analysis Of The Inferences Of Dry Intrusion On The Heavy Rain Process Of June 18-26, 1998

Based on NCEP and other observational datasets, a severe heavy rainfall process occurred in the south of china during June 18-19,1998 was investigated. The first diagnostic analyses show that the strong rainfall are produced by vortex, shear line and upper and lower jets, stationary front. The condition of high energy, saturation, potential instability is propitious to the form and maintenance of this rainfall. The result of numerical simulation by MM5 model shows that convection takes place on shear line, vortex and θe front .Owe to the coupling of upper and lower tropospheric jet streams , sinking motion to the left side of upper jet streams score and ascent between the right side of upper jet streams score and the left side of the lower jet stream score produce the secondary circulation. The dry intrusion air gliding along steep θe front causes the development of vortex.. Diagnostic of moist potential vorticity (MPV) apparent heating source (Q1) and apparent moisture sink (Q2) and helicity indicate that it is moist symmetry instabSe and convective at the troposphere, and that it is moist symmetric instable and unconvective on the θ e front. and that the severe heavy rainfall is related with them closely.