Microrain Radar Observation Study On Microphysical Vertical Structure Characteristics Of Several Typical Precipitations In Beijing

In this paper,the observation data of several typical precipitation processes in Beijing using micro rain radar(MRR),and Combined with the observation of two-dimensional video raindrop spectrometer(2DVD),the characteristics of the microphysical vertical structure of these typical precipitation clouds are analyzed and studied.In the first place,quality control with rainfall observation data observed by MRR radar,correct the attenuation of radar electromagnetic waves caused by raindrops,removing the effect of vertical airflow on the end velocity of raindrops.On this basis,deduced the reflectance factor Z,raindrop effective diameter ED,and total raindrop concentration N₀ vertical distribution of these rainfall parameters.Afterward,analyzed the vertical structure and variation characteristics of rainfall in several typical precipitation clouds in Beijing in summer.Finally,analyzed the vertical structural characteristics of the equivalent reflectance factor Ze and the snowfall rate S in Zhangjiakou during a winter snowfall by Doppler spectral integration.The main conclusions:(1)Correction of the Radar Electromagnetic Wave Attenuation Caused by the Rain Drop-by-Library Correction Algorithm,reflectivity factor before and after contrast correction,attenuation compensation is mainly concentrated between 30-38d BZ.(2)Using the low-end algorithm of the velocity spectrum and the algorithm of average terminal velocity to eliminate the impact of vertical airflow on the end velocity of raindrops during summer stratified cloud rainfall and convective cloud rainfall.Compare the rainfall intensity before and after the correction at 300m of the MRR radar with the 2DVD,before the removal,the change trend of the rainfall intensity of the two is basically the same,but the value is quite different,after excluding,whether it is the change trend or the value,the degree of agreement is higher.Before and after removing the effect of vertical airflow,the relative error of stratified cloud rainfall decrease by about 33%,the relative error of convective cloud rainfall decrease by about 42%,improved error from actual value.(3)Summer rains from different cloud systems(stratified clouds,convective clouds,mixed clouds)in the vertical direction,Z,R,LEC,N₀,ED the same trend with height.Stratified cloud rainfall lasts for a long time but the rainfall intensity is low,Z_maxis 40d BZ,near-ground instantaneous R_max is about 10mm/h,the maximum LWC is1g/m³,the maximum ED is 1.4mm.Convective cloud rainfall duration is short but rainfall intensity is high,Z close to 50d BZ,the instantaneous R_max near the ground is120mm/h,the maximum LWC is 45g/m³.Long-lasting rain of mixed clouds,sudden increase in rainfall intensity,Z exceeds 40d BZ but less than 50d BZ.At the beginning of the rain,stratified and convective rain rainfall parameters decrease with height,rainfall parameters of mixed cloud rainfall increase with decreasing height.(4)Due to the influence of different microphysics,make the average raindrop spectrum of different cloud systems in summer have different characteristics in the vertical direction.The raindrop spectrum pattern of stratified cloud rainfall is relatively stabilize,the maximum number of raindrops is 10⁸mm^-1m^-3,most particles with raindrop diameter less than 1mm.Instability of raindrop spectral pattern of rainfall in convective and cumulus clouds,dramatic change,the maximum number of convective rains is 10¹⁰ mm^-1m^-3,the diameter of raindrop particles is too large.The density of raindrops in mixed cloud rainfall is between that of stratified and convective clouds,most droplets and medium droplets with diameter less than 1.7mm,the broadest average raindrop spectrum.(5)Calculate the equivalent reflectance factor Z_e and the snowfall rate S by an algorithm that directly integrates the Doppler spectrum,reduce errors from actual snowfall parameters,Z_e and S both increase with decreasing height.