Numerical Simulation And Diagnostic Analysis Of Doppler Weather Radar Features On A Heavy Convective Storm

The heavy convective storms such as heavy rain,hail, squall line, tornado and thunder etc. are disastrous weather, which endanger not only agriculture but also the building and highway. Because the heavy convective storms have small spatial and time scale, it hard to predict them exactly. In this thesis we first analyze the weather climate background and the characteristic of the strong convection ( hail) in the province of Gansu . And then select a heavy convective storm occurred on middle part of Gansu province. By using the diagnostic analysis of the non-hydrostastic model numerical simulation result the cause of heavy convective storm. The result shows that this is the typical Mongolia vortex situation. Along the vortex bottom cold air moves eastward. The south wind at low levels is established to prepare the abundant vapour condition for the severe convective storm formation. The instability energy area has existed on the morning of 28 and developped very quickly after noon because of the role of terrain and local heat convection. The ground cold front that through Gansu middle part causes the low levels flow convergent suddenly and revolving, rising intensely .This triggeres the unstable energy release and provides the dynamic condition for the the strong convection weather. Analysis of the storm relative helicity and the energy-helicity index (EHI) shows the strong convection weather usually appear at the right of high area of the storm relative helicity and late l-2hours of high area of the energy-helicity index. The EHI value of hail weather is bigger than the value of rainstorm .In the paper, a detailed analysis is made , by using the Gaolan mountain in Lanzhou CINRAD/CC Doppler weather radar data on a severe convective storm which occured in the middle of Gansu province on 30 may 2005 from 15:00 to 19:00. It is found that the squall was the main mesoscale convective system that caused the severe convective storm. The storm first appeared at 15: 00, then moved to the southeast direction , from 16: 15 to 17: 03, the multi-cell storm became more strongly and evolved into the supercell storm with the characteristics of the vortex zonal echoes and band echo. There were two obvious outflow boundary observed in south of the supercell, lying to the southwest and southeast of the hook echo of thestorm , respectively. The shape of the low elevation reflectivity in the left front flank of the supercell was an inverted "V", the maximum echo intensity appeared in the weak echo zone with the value over 70 dBz., The corresponding radar velocity maps showed a strong mesocyclone.In this period the maximum vertical integrated liquid water (VIL) reached above 70kg/m2 and the echo top(ET) is 17-18km. Hence, this storm possessed the typical features of supercell storms.