Ground-Based Remote Sensing of Stratocumulus Properties during CLARA, 1996
Ground-Based Remote Sensing of Stratocumulus Properties during CLARA, 1996
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1996 年 CLARA 期间层积云特性的地面遥感
DOI：
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发表时间：
2000
期刊：
影响因子：
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通讯作者：
Schm Suzanne Jongen
中科院分区：
文献类型：
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作者：
R. Boers;H. Russchenberg;J. Erkelens;V. Venema;V. Lammeren;A. Apituley;Schm Suzanne Jongen
提出了一种利用地面遥感资料反演水云水滴浓度的方法。它依赖于云的厚度，液态水路径和云底附近的光学消光的观测。该方法进行了测试的两个案例研究（1996年4月19日和1996年9月4日）期间的云和辐射实验（CNOAA）。该实验的目的是在荷兰西部的德尔夫特市附近使用各种遥感仪器观测云层。云厚的测量依赖于激光雷达对云底和云顶的探测。结果表明，在COSTA期间，使用当前的激光雷达技术，可以检测到云底的不确定性小于30米。雾滴浓度的现场观测与遥感观测之间的一致性较好。误差分析表明，该方法对液态水路径的不确定性和多次散射对激光雷达信号回波的未知影响最为敏感。当液态水路径非常小时，液态水路径的相对误差增加到不可接受的水平，使得液滴浓度的检索变得非常困难。多重散射强度的估计不确定性可以解释一天的液滴浓度观测和反演之间的差异，但不能解释另一天。
A method is presented to obtain droplet concentration for water clouds from ground-based remote sensing observations. It relies on observations of cloud thickness, liquid water path, and optical extinction near the cloud base. The method was tested for two case studies (19 April 1996 and 4 September 1996) during the Clouds And Radiation experiment (CLARA). The CLARA experiment was designed to observe clouds using a variety of remote sensing instruments near the city of Delft in the western part of the Netherlands. The measurement of cloud thickness is dependent on the detection of cloud base by lidar and cloud top by radar. It is shown that during CLARA it was possible to detect cloud base with an uncertainty of less than 30 m using current lidar techniques. The agreement between in situ and remote sensing observations of droplet concentration was reasonable. An error analysis indicates that this method is most sensitive to uncertainties in liquid water path and the unknown effects of multiple scattering on lidar signal returns. When the liquid water path is very small the relative error of the liquid water path increases to unacceptable levels, so that the retrieval of droplet concentration becomes very difficult. The estimated uncertainty in the strength of multiple scattering can explain differences between observations and retrievals of droplet concentration on one day, but not the other.