Assessment Of The Lidar Ratio And Enhancement Of The Results From The Ground-Based Raymetrics 355-NM Lidar
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Date
2017-08
Authors
Khor, Wei Ying
Journal Title
Journal ISSN
Volume Title
Publisher
Universiti Sains Malaysia
Abstract
Lidar signal processing to obtain lidar results such as the aerosol optical depth (AOD) requires two important parameters which are the lidar ratio (LR) value and the range corrected signals (RCS). LR values estimated is less accurate and requires a complicated method while the RCS is contaminated with noise. Therefore, the lidar results obtained after inversion of the lidar signals is less accurate. The objectives of this study are to develop an equation with optimized parameters to estimate LR values, to increase signal-to-noise ratio (SNR) to a value of more than 50, and to validate and enhance the lidar results. An equation to estimate the LR values is obtained through multiple regression and the LR values for year 2014 are estimated. The RCS is de-noised using the wavelet de-noising method. Both methods are combined to enhance the lidar results. The estimated LR values lie in the range from 45 to 80 sr which are similar to LR values obtained from other literature. The de-noising method has increased the SNR to an average of 71.81 with a root mean squared error (RMSE) of 4.48. Noise is removed from the signals but some of the details in the signals are also removed which affects the interpretation of the features of the atmosphere. De-noising the signals has not increased the range of detection. Comparison with the AERONET AOD values show that there is improvement in the lidar results after applying the enhancement method with a coefficient of determination of 0.8560. The correlation between AERONET and lidar increased to 92.5%. As a conclusion, the LR values are assessed and the lidar results are enhanced.
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Keywords
Lidar signal processing , to obtain lidar results.