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Proceedings Paper

Characterization of aerosol backscatter-to-extinction ratio from multiwavelength and multi-angular lidar profiles
Author(s): Michael Sicard; Francesc Rocadenbosch; Miguel Angel Lopez; Adolfo Comeron; Alejandro Rodriguez; Constantino Munoz; David Garcia-Vizcaino
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Paper Abstract

The newly developed Nd:YAG portable 3-D-scanning lidar from the Universitat Politecnica de Catalunya (UPC, Technical University of Catalonia, Barcelona, Spain) was used to improve our knowledge of the aerosols properties in the Barcelona area where an important number of pollution and saharan dust events can be observed all year round in the atmosphere. The system simultaneously operated at the 1064-nm and 532-nm elastic wavelengths, and was used in its scanning mode from 15 degrees to 70 degrees from zenith with 5 degree steps. A variational method was used to invert the multi-angular profiles and to retrieve the aerosols optical thickness and backscatter coefficient at each wavelength without making any assumption on the aerosol type. At the same time, the ratio of the backscatter profiles was used to retrieve the profile of the Angstrom coefficient in backscatter. The backscatter-to-extinction ratio could not be calculated directly but various values of this parameter were used in Klett method until backscatter coefficient profiles could match the one retrieved with the variational method (at least in some altitude regions). Very good agreement (differences less than 20%) was observed in the 0.3 - 2.5 km region with a value of 0.030 sr-1, whereas no agreement could be achieved above where supposedly mixed aerosols were initially observed. The lidar profiles closer to the zenith at both wavelengths allowed to calculate a new Angstrom coefficient in backscatter that is compared to the one retrieved by the variational method. The comparison showed good agreement in the lower layers and thus validated the backscatter-to-extinction ratio profiles used in the Klett method. However, the difficulties encountered to invert the lidar signal above an altitude of 1.6 km show that non negligible inhomogeneities of the atmosphere were present in each line of sight, proving the dense and fast-moving aerosol load over the Barcelona basin.

Paper Details

Date Published: 18 April 2003
PDF: 9 pages
Proc. SPIE 4882, Remote Sensing of Clouds and the Atmosphere VII, (18 April 2003); doi: 10.1117/12.477560
Show Author Affiliations
Michael Sicard, Univ. Politecnica de Catalunya (Spain)
Francesc Rocadenbosch, Univ. Politecnica de Catalunya (Spain)
Miguel Angel Lopez, Univ. Politecnica de Catalunya (Spain)
Adolfo Comeron, Univ. Politecnica de Catalunya (Spain)
Alejandro Rodriguez, Univ. Politecnica de Catalunya (Spain)
Constantino Munoz, Univ. Politecnica de Catalunya (Spain)
David Garcia-Vizcaino, Univ. Politecnica de Catalunya (Spain)

Published in SPIE Proceedings Vol. 4882:
Remote Sensing of Clouds and the Atmosphere VII
Klaus P. Schaefer; Olga Lado-Bordowsky; Adolfo Comeron; Richard H. Picard, Editor(s)

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