基于激光雷达资料的小波变换法反演边界层高度的方法

摘要

When applying wavelet transformation method in the retrieval of the boundary layer height by using lidar backscatter signals, the different selection of wavelet generating function may get different results. Therefore,the idealized lidar signal profiles during the daytime and nighttime have been built to explore which wavelet generating function will get the best performance. In this study,Haar wavelet covariance transformation has been used for the profiles of lidar backscatter signal,and Morlet and Mexican Hat wavelet trans-formation have been utilized for the gradient profiles of lidar backscatter signal,respectively. The results showed that the Haar function and the Mexican Hat function should be used as wavelet generating functions:the Haar function is more accurate and the Mexican Hat function is more stable. Furthermore,the changed wavelet dilation of the wavelet generating function also has been researched in order to test the sensitivity of the three different wavelet transformation methods to the wavelet dilation. The result show that whatever the ide-alized profile or the profile in which disturbance was added,the larger wavelet dilation can get a more stable and accurate diurnal boundary layer height and nocturnal mixing layer height.%利用小波变换法反演边界层高度时，不同小波母函数的选取可能得到不同的边界层高度。因此，对构造的白天及夜间激光雷达后向散射信号理想廓线进行Haar小波协方差变换，并对后向散射信号梯度廓线进行Morlet与Mexican Hat小波变换反演边界层高度。结果表明，宜采用Haar函数与Mexican Hat函数作为小波母函数，其中Haar函数准确性优于Mexican Hat函数，而Mexican Hat函数更易稳定。同时为了进一步检验3种小波变换法的反演结果对小波振幅的敏感性，通过改变小波母函数的小波振幅，发现无论是理想廓线还是叠加扰动的廓线，较大的小波振幅易得到比较稳定准确的白天边界层高度与夜间混合层高度。