Vertical Structure Distribution And Evolution Of Different Cloud Systems Based On Micro Rain Radar

It had important meaning for more-refined forecast of precipitation and weather modification to study the structure of precipitation and the characteristics of precipitation microphysical process.Taking the Micro Rain Radar(MRR)analysis as the core,this research studied the vertical distribution and evolution properties of two precipitation processes by using Ka band MRR in Xingtai,Hebei,This research also combined a mixed cloud and a stratiform precipitation process which is observed by ground disdrometer,rain gauge,laser ceilometer and weather radar.The comparability of observed result has been studied combining the MRR with weather radar,disdrometer and rain gauge.The reliability of MRR data has been examined.The feature of the mean vertical distribution in the characteristic quantity and the raindrop-size distribution about two precipitation process and different precipitation phase has been studied,which combined MRR with disdrometer and laser ceilometer.Meanwhile,the evolution feature of the characteristic quantity and the raindrop-size distribution which changed by the time and altitude has been analyzed.The main results are as follows:(1)To compare with the rain gauge,the accumulative rainfall which gets from the MRR detection is smaller.But the trend of observed result from two instruments is consistent.The result of MRR 200m is very close to the disdrometer rain rate.The mean variation of the rain rate is 0.05 mm · h-1?0.09 mm · h-1,respectively.The correlation coefficient is both 0.93.According to the MRR observation,the small drop concentration is overrated;the large drop concentration is underestimated;the medium concentration is more consistent compared with the disdrometer.(2)From the vertical distribution of the characteristic quantity,as the height goes down,the mean reflectance has increased in lower layers in two precipitation process.The vertical variation of raindrop spectrum between two processes is different in the 1 ower layer,and there are also differences in the characteristics of raindrop spectrum within an d outside the cloud.Above the mean cloud-base height,the change of the small drop concentration is less;the medium and the large drop concentration are increased in two process.It shows that there is the collision-coalescence process between rain drops and cloud droplet.But under the mean cloud-base,the small drop concentration decreases with a reduction in height because of obvious evaporation process.In the mixed cloud precipitation process,the small drop concentration and the large drop concentration is obviously reduced and increased with the height decrease,respectively,in lower layer.This indicates that the collision-coalescence process between the raindrops is stronger.However,the raindrop-size distribution of the stratiform precipitation has the small change in lower layer.(3)The vertical distribution of precipitation exists discrepancy during different precipitation periods.In the early mixed cloud precipitation process,the mean reflectance and the rain rate both has obviously reduce under the cloud base.Compared to the intracloud,the liquid water content and the total raindrop concentration below the cloud base is significantly reduced in the early precipitation;while the evaporation has the strong impact.At the stage of stable light precipitation,the change of the characteristic quantity and the raindrop-size distribution along with the height is small.At the stage of heavy precipitation,as the height goes down,the mean reflectance has the significantly increased;the spectral width of raindrop-size distribution is broadened;the small drop concentration has significantly reduced and the large drop concentration has significantly increased.Based on the above,the coalescence growth between the raindrops is strong at the stage of heavy precipitation.