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A comparison of lidar inversion methods for cirrus applicationsSeveral methods for inverting the lidar equation are suggested as means to derive the cirrus optical properties (beta backscatter, alpha extinction coefficients, and delta optical depth) at one wavelength. The lidar equation can be inverted in a linear or logarithmic form; either solution assumes a linear relationship: beta = kappa(alpha), where kappa is the lidar ratio. A number of problems prevent us from calculating alpha (or beta) with a good accuracy. Some of these are as follows: (1) the multiple scattering effect (most authors neglect it); (2) an absolute calibration of the lidar system (difficult and sometimes not possible); (3) lack of accuracy on the lidar ratio k (taken as constant, but in fact it varies with range and cloud species); and (4) the determination of boundary condition for logarithmic solution which depends on signal to noise ration (SNR) at cloud top. An inversion in a linear form needs an absolute calibration of the system. In practice one uses molecular backscattering below the cloud to calibrate the system. This method is not permanent because the lower atmosphere turbidity is variable. For a logarithmic solution, a reference extinction coefficient (alpha(sub f)) at cloud top is required. Several methods to determine alpha(sub f) were suggested. We tested these methods at low SNR. This led us to propose two new methods referenced as S1 and S2.
Document ID
19920021830
Acquisition Source
Legacy CDMS
Document Type
Conference Paper
Authors
Elouragini, Salem
(Ecole Polytechnique Palaiseau, France)
Flamant, Pierre H.
(Ecole Polytechnique Palaiseau, France)
Date Acquired
September 6, 2013
Publication Date
July 1, 1992
Publication Information
Publication: NASA. Langley Research Center, 16th International Laser Radar Conference, Part 2
Subject Category
Instrumentation And Photography
Accession Number
92N31074
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.

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