NDLI: Using Combined 532 NM HSRL and 1064 NM Elastic-Scatter Lidar Observations to Verify and Update CRAM Dual-Wavelength Aerosol Retrieval Models

Content Provider	IEEE Xplore Digital Library
Author	Reagan, J.A. McPherson, C.J. Ferrare, R. Hostetler, C. Hair, J.
Copyright Year	2008
Description	Author affiliation: Univ. of Arizona, Tucson, AZ (Reagan, J.A.; McPherson, C.J.)
Abstract	The widely employed Fernald lidar equation solution relation retrieves aerosol backscatter versus height for an assumed aerosol extinction-to-backscatter ratio, $S_{a},$ and known system calibration factor, C, at a given wavelength, subject to the constraint/assumption that $S_{a}$ is spatially constant over the solution layer (height range). At 532 nm, the calibration factor may be estimated fairly accurately by Rayleigh (molecular) normalization in high-altitude, clean-air regions. For elevated aerosol layers embedded in clean air, the direct transmittance approach may be used to estimate the optical depth of the layer, thereby giving an auxiliary input that permits $S_{a}$ to be determined as a part of the solution. Otherwise, $S_{a}$ must be specified based on models or determined through use of some other constraining information. The retrieval at 1064 nm is more problematic because the molecular scatter contribution is much weaker, typically making it difficult to either calibrate by molecular normalization or to accurately estimate the transmittance of an elevated aerosol layer, particularly for the weak signals from satellite lidar or eye-safe airborne lidar. As such, aerosol retrievals from dual-wavelength satellite lidars such as those onboard ICESat and CALIPSO have largely been limited to 532 nm retrievals using a table look-up approach to select assumed $S_{a}$ values based on climatological/geographically determined models. Dual-wavelength retrievals using a Constrained Ratio Aerosol Model-fit (CRAM) retrieval method, employing AERONET based model ratio parameters, have also been obtained with some success for a few satellite lidar data sets.
File Size	111868
File Format	PDF
ISBN	9781424428076
DOI	10.1109/IGARSS.2008.4779055
Language	English
Publisher	Institute of Electrical and Electronics Engineers, Inc. (IEEE)
Publisher Date	2008-07-07
Publisher Place	USA
Access Restriction	Subscribed
Rights Holder	Institute of Electrical and Electronics Engineers, Inc. (IEEE)
Subject Keyword	Laser radar Aerosols Backscatter Information retrieval Extinction coefficients Calibration Satellites NASA Optical scattering Hair
Content Type	Text
Resource Type	Article

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