利用KAZR云雷达对SACOL站云宏观特性的研究  

Cloud macrophysical properties from KAZR at the SACOL

作　　者：朱泽恩 郑创 葛觐铭[1] 黄建平[1] 付强[1] ZHU ZeEn ZHENG Chuang GE JinMing HUANG JianPing FU Qiang(Key Laboratory of Semi-Arid Climate Changes with the Ministry of Education, School of Atmospheric Sciences, Lanzhou University, Lanzhou 730000, Chin)

机构地区：[1]兰州大学半干旱气候变化教育部重点实验室,兰州730000

出　　处：《科学通报》2017年第8期824-835,共12页Chinese Science Bulletin

基　　金：国家自然科学基金(41430425;41575016;41521004;41375021);兰州大学中央高校基本科研业务费专项(LZUJBKY-2016-k01)资助

摘　　要：云是气候系统中最为重要的因子之一,对地气系统的辐射收支有显著影响.然而由于云在气候模式中的表征和反馈作用不能很好地被描述,因而也是造成气候预测存在较大不确定性的重要因子.兰州大学半干旱气候与环境监测站(SACOL)于2013年7月引进了Ka-Band Zenith Radar(KAZR),在西北干旱区进行云的长期连续观测.本文利用云雷达观测数据,首先实现了目前ARM用于云检测的业务算法.在此基础上对2014年SACOL站上空云宏观特性进行统计,初步分析了云底、云顶和云厚的分布变化,结果表明:云底在1.5和5.5 km处出现频率最高,云顶发生频率在2.5和8.5 km处达到峰值;67%的云层厚度分布在2 km以内;月平均总云量的发生频率为44%~76%,低云、中云和高云的发生频率分别为13%,30%和34%;单层云、双层云和三层云占到云总数的98%,其中夏秋季节多层云发生频率较高;各个季节不同类型的云都具有一定的日变化特征;通过KAZR与Cloud Sat和CALIPSO卫星的观测比对,结果表明Cloud Sat对厚云的穿透性好,但无法探测到反射率因子低于?30 d BZ的弱云,CALIPSO对弱云最敏感,但信号受云滴粒子衰减较快,对于厚度较大的云探测的云底高度偏高.Clouds are one of the most important components in the climate system through their profound effects on the radiative energy budget. However, due to the lack of accurate representation of clouds in global climate models, they are the major source of uncertainties for the future climate projections. Millimeter wavelength Cloud Radars （MMCRs） are powerful instruments that can resolve vertical structure as well as microphysical properties of clouds. The wavelength of MMCRs, which is shorter than those of weather radars, allows an excellent sensitivity to cloud droplets and ice crystals while being much longer than lidar wavelengths enables MMCRs to penetrate multiple cloud layers. Ka-Band Zenith Radar （KAZR）, which has been deployed at the Semi-Arid Climate and Environment Observatory of Lanzhou University （SACOL） since July 2013, has been continuously operated for three years. By applying a cloud mask algorithm that is operationally employed in the Atmospheric Radiation Measurement Program to distinguish radar echoes from noise, we analyze the macrophysical properties of clouds above the SACOL site by using the KAZR observations through 2014. It is shown that the occurrence of cloud base peaks at both 1.5 and 5.5 km while the cloud top peaks at 2.5 and 8.5 km. About 67% of the cloud thickness is within 2 km. The heights of cloud base and top in spring and summer are higher than autumn and winter. The diurnal cycles of cloud top and base are significant in summer and autumn but not in spring and winter. In summer, both the cloud base and top heights increase after sunrise and then decrease from mid-afternoon to midnight, while the cloud base and cloud top heights increase from noon to midnight in autumn. These seasonal features of diurnal changes may be closely related to the cloud formation mechanism and seasonal variations of solar radiation. Clouds over the SACOL can be classified as low, middle and high clouds based on the cloud height and thickness. The monthly mean occurrence of all clouds varies b

关 键 词：云雷达(KAZR) 信号识别 云宏观特性 CLOUD SAT 云-气溶胶激光雷达和红外探测者卫星观测(CALIPSO) 

分 类 号：P412.25[天文地球—大气科学及气象学]