Fractal properties and denoising of lidar signals from cirrus clouds
Fractal properties and denoising of lidar signals from cirrus clouds
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DOI：
10.1029/1999jd900972
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发表时间：
2000-02
影响因子：
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通讯作者：
J. V. D. Heuvel;M. L. Driesenaar;R. Lerou
中科院分区：
文献类型：
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作者：
J. V. D. Heuvel;M. L. Driesenaar;R. Lerou
对卷云的机载激光雷达信号进行分析，以确定云的结构。气候模拟和数值天气预报受益于卷云的精确模拟。对欧洲激光雷达空间技术实验（ELITE）活动中的机载激光雷达测量数据进行了分析，通过组合镜头获得了恒定高度下的后向散射。对高空信号进行了卷云水平结构分析。功率谱和结构函数在双对数图上显示为直线。这种行为是布朗分形的特征。使用Haar小波的小波分析证实了分形方面。结果表明，卷云的水平结构可以描述的分形维数为1.8的长度尺度上，变化4个数量级。我们使用分形特性在一个新的去噪方法。未来从太空进行低信噪比的激光雷达测量需要进行降噪。我们的小波去噪是基于Haar小波，并使用卷云的统计分形特性的最大后验概率（MAP）的基础上的方法。这种基于小波的去噪方法在ELITE机载激光雷达信号上进行了测试，使用了附加的高斯噪声。获得了关于平均的上级结果。美国地球物理联合会版权所有2000年。
Airborne lidar signals of cirrus clouds are analyzed to determine the cloud structure. Climate modeling and numerical weather prediction benefit from accurate modeling of cirrus clouds. Airborne lidar measurements of the European Lidar in Space Technology Experiment (ELITE) campaign were analyzed by combining shots to obtain the backscatter at constant altitude. The signal at high altitude was analyzed for horizontal structure of cirrus clouds. The power spectrum and the structure function show straight lines on a double logarithmic plot. This behavior is characteristic for a Brownian fractal. Wavelet analysis using the Haar wavelet confirms the fractal aspects. It is shown that the horizontal structure of cirrus can be described by a fractal with a dimension of 1.8 over length scales that vary 4 orders of magnitude. We use the fractal properties in a new denoising method. Denoising is required for future lidar measurements from space that have a low signal to noise ratio. Our wavelet denoising is based on the Haar wavelet and uses the statistical fractal properties of cirrus clouds in a method based on the maximum a posteriori (MAP) probability. This denoising based on wavelets is tested on airborne lidar signals from ELITE using added Gaussian noise. Superior results with respect to averaging are obtained. Copyright 2000 by the American Geophysical Union.