Transmittance ratio constrained retrieval technique for lidar cirrus measurements

Center for Atmospheric Sciences, Department of Atmospheric and Planetary Sciences, Hampton University, Hampton, Virginia 23668, USA.
Optics Letters (Impact Factor: 3.29). 05/2012; 37(9):1595-7. DOI: 10.1364/OL.37.001595
Source: PubMed


This letter describes a lidar retrieval technique that uses the transmittance ratio as a constraint to determine an average lidar ratio as well as extinction and backscatter coefficients of transparent cirrus clouds. The cloud transmittance ratio is directly obtained from two adjacent elastic lidar backscatter signals. The technique can be applied to cirrus measurements where neither the molecular scattering dominant signals above and below the cloud layer are found nor cloudfree reference profiles are available. The technique has been tested with simulated lidar signals and applied to backscatter lidar measurements at Hampton University, Hampton, Virginia.

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    • "With the simple setup and suitability to operate on a routine basis, elastic backscatter lidars have been proven to be a very useful remote sensing tool. Systems have been developed to make measurements of aerosols and clouds from the ground, on a boat, air plane and even onboard a satellite (Gerrit and Gerard, 1992; McCormick, 1995; Strawbridgea and Snyderb, 2004; Winker et al., 2007; Müller et al., 2007; Vaughan et al., 2010; Su et al., 2012). Because the elastic lidar equation includes two unknown variables (backscatter and extinction), an assumption on a constant extinction-to-backscatter ratio (or lidar ratio) has to be made to solve the lidar equation in the data processing of single wavelength backscatter measurements (Fernald et al., 1972; Kovalev et al., 2007). "
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    ABSTRACT: We advance a novel retrieval technique that combines a Raman and multi-wavelength elastic backscattered signals to retrieve multi-wavelength lidar ratio profiles of aerosol. With profile of backscatter coefficients at 355 nm retrieved from elastic backscatter signal at 355 nm and Raman scattering signal at 387 nm, lidar ratio profiles can be calculated at 532 nm and 1064 nm from the elastic backscatter signals at these wavelengths, taking advantage that the 532 nm/355 nm and 1064 nm/355 nm backscatter ratios are generally approximately equal for two neighboring range bins. This technique has been tested using numerical simulations and applied to lidar measurements at the Hampton University, Hampton, Virginia.
    Full-text · Article · Nov 2013 · Atmospheric Environment
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    ABSTRACT: An improved method that has the potential to improve the retrieval of aerosol optics properties (backscatter/ extinction coefficients) from elastic–Raman lidar data is presented. Aerosol backscatter coefficients can be retrieved by choosing the reference height at near-range rather than conventional far-range when the signal-to-noise ratios are low at the far-range or aloft aerosol layers and clouds appear there. Significant retrieval errors in aerosol backscatter coefficients caused by large uncertainties of the aerosol reference value at far-range can be reduced. To avoid the ill-posed retrievals of aerosol extinction from the conventional Raman method, the new method derives the aerosol extinction and lidar ratio with the constrained Fernald inversions by independent aerosol backscatter coefficients from above proposed method. 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.
    Full-text · Article · Jul 2013 · Applied Physics B