Ms. Liqiao Lei Profile

Liqiao Lei

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Proceedings Article | 20 May 2013 Paper

A new method to retrieve aerosol extinction coefficients from elastic-Raman lidar data

Jia Su, M. Patrick McCormick, Liqiao Lei

Proceedings Volume 8731, 87310J (2013) https://doi.org/10.1117/12.2014927

KEYWORDS: Aerosols, LIDAR, Signal attenuation, Backscatter, Raman spectroscopy, Mass attenuation coefficient, Atmospheric particles, Scattering, Optical properties, Raman scattering

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Atmospheric aerosols have a significant impact on climate change through the scattering and absorption of incoming solar and outgoing thermal radiation. The aerosol optical properties can be directly measured using an elastic-Raman lidar. However, extraction of the extinction coefficient from the optical depth profile requires the use of numerical differentiation with these lidars, which suffers the random and systematic noises limitation and thereby reducing the detection sensitivity and accuracy. A new method to improve the quality of Raman lidar data processing is presented. Compared to the conventional method, the proposed method has the advantage, which can directly retrieve the aerosol extinction coefficients without numerical differentiation. Trial values of lidar ratio (from 10 to 90 sr with an increment of 1 sr) are applied to Fernald solution of the elastic lidar signals at 354.7 nm and all aerosol backscatter coefficients are obtained. The exact aerosol backscatter coefficients retrieved by combing elastic and Raman signals are used as constrain of these results of Fernald method to determine aerosol true lidar ratios as well as extinction coefficients. The numerical simulations demonstrated that the proposed method provides good accuracy and resolution of aerosol profile retrievals. And the method is also applied to elastic-Raman lidar measurements at the Hampton University, Hampton, Virginia.

Proceedings Article | 20 May 2013 Paper

Planetary boundary layer detection with fractal dimension of three-wavelength lidar signals

Liqiao Lei, M. Patrick McCormick, Jia Su

Proceedings Volume 8731, 873112 (2013) https://doi.org/10.1117/12.2014772

KEYWORDS: LIDAR, Fractal analysis, Signal detection, Backscatter, Aerosols, Atmospheric particles, Signal processing, Clouds, Atmospheric sensing, Molecular lasers

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Lidar backscatter signal resulting from laser light scattering from the aerosol and molecular in the atmosphere contains various information about the geometrical and physical properties of aerosol and molecular. The lidar backscatter signal can provide information about the planetary boundary layer (PBL) stratification by using aerosol as a tracer for convective and mixing processes. A PBL height and structure detecting technique based on the fractal dimension of three-wavelength backscatter signals is advanced. In this PBL height detecting technique, the three-wavelength backscatter signals are obtained by the Hampton University (HU, 37.02° N, 76.33° W) lidar. The fractal dimension was calculated using the three-wavelength lidar signals. The PBL heights obtained from fractal dimension of threewavelength lidar signals is compared with PBL heights obtained from the potential temperature profiles which are provided by NASA Langely Research Center (10 miles from HU). And results of the two methods agree well. Moreover, fractal dimension method can reduce the influence of the geometrical form factor on the PBL detecting to expand the detecting range of PBL and remove the effect of plume. Also, the fractal dimension method can show the PBL dynamics and the PBL evolution clearly.

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