云底高度的地基毫米波云雷达观测及其对比

Observation and Comparison of Cloud-base Heights by Ground-based Millimeter-wave Cloud Radar

对2014年11月20日-12月31日中国气象局大气探测综合试验基地Ka波段毫米波云雷达、Vaisala CL51激光云高仪、L波段高空探测系统观测的云底高度进行对比分析。结果表明:在低能见度条件下,毫米波云雷达对云的探测能力明显优于激光云高仪,随着能见度的增加,两设备云探测能力差距在减小;毫米波云雷达与激光云高仪同时观测到有云时,二者观测的云底高度相关系数为0.92;毫米波云雷达与探空观测云底、云顶高度的相关系数分别为0.93和0.78;云雷达观测的云底高度均略低于激光云高仪和探空,云雷达观测的云顶高度略高于探空。

As cloud automatic observation achieved breakthrough progress,a long-term comparison test on different devices is needed to select the suitable cloud observation equipment for regular operation of China.A Ka-band millimeter-wave(35 GHz) cloud radar(KaCR) and a vaisala laser ceilometer(VCEIL) are installed in Meteorological Observation Center of CMA,and data are compared with L-band rawinsonde observations(LRAOBS) in Beijing Weather Observatory from 20 Nov to 31 Dec in 2014.Among these instruments,the KaCR observes the echo power value and its temporal resolution is from 1 s to 60 s,the VCEIL measures the back scattering intense data with the same temporal resolution of KaCR,and the LRAOBS works twice every day.Data acquisition ratio measured by KaCR and VCEIL under different visibility conditions are compared.A comparison test of cloud base heights and cloud top heights measured by KaCR and VCEIL is also carried out.A comparison test of cloud base height and cloud top height measured by KaCR and LRAOBS and a real example is analyzed.And the cloud base heights and cloud top heights measured by KaCR,VCEIL and LRAOBS during a precipitation process are compared too.The result indicates that the detection ability of KaCR is better than VCEIL under low visibility condition,and their difference of detection ability reduces with the visibility increasing.The cloud base heights measured by KaCR and VCEIL are well consistent,with the correlation coefficient reaching 0.92.The correlation coefficient of cloud base height between KaCR and LRAOBS is about 0.93,and that between KaCR and LRAOBS is about 0.78.Cloud base height measured by KaCR is slightly lower than that measured by VCEIL and LRAOBS,and cloud top height measured by KaCR is slightly lower than that measured by LRAOBS.KaCR can clearly show the process of cloud formation and dissipation and the structure changes of cloud compared with VCEIL and LRAOBS,but cannot accurately identify the cloud base position when it rains.