Analysis on Cold Front Cloud Structure from 95 GHz Cloud Radar Data

The cloud structure of a cold front on November 5-7,2008 is analyzed using the comprehensive observed data from ARM project in Shouxian,Anhui Province,including cloud radar,ground microwave radiometer,sounding and ground observation data.The results show that the particle′s morphology and size can be preliminarily determined through the Doppler radar speed of cloud and whether or not it presence snow crystals or rain.Near 0 ℃ level there is a dark band,which is caused by the 3 mm wavelength radar to strong attenuation of the snow crystals and the Rayleigh scattering;cloud radar observation can identify clearly melt layer.It is found that the cloud structure is very uneven,there is a hydrometeor content big value area between 5~7 km.In this area,grown snow and ice crystal fall continuously to lead to the cloud base gradually stretched downward and produce an intermittent precipitation.Below 2 km above the warm area there is dry and cold northeast airflow,which limit the raindrop growth through the warm rain process,the precipitation intensity of front surface is caused to be small.The posterior between 4~7 km heights,because the snow and ice crystal settlement,the relative humidity is small,the clouds are split into two-layer-clouds.There is severe precipitation after the cold front,which is caused mainly by the warm rain process.