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Proceedings Paper

Long-path method for measurement of spectrally resolved particle attenuation
Author(s): Bo Galle; Johan M. Mellqvist
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Paper Abstract

A method is described which makes possible the recording of absolute atmospheric absorption spectra. The method is based on optical long path absorption spectroscopy and thus integrates the optical properties over a measurement path, typically one kilometer. Cancellation of instrument factors are achieved by ratioing spectra from two nearly collinear paths of different length recorded close in time. The method is demonstrated for measurement of spectrally resolved particle extinction in the wavelength region 275 - 300 nm, a physical parameter needed for the correction of LIDAR ozone measurements. By the use of differential optical absorption spectroscopy, (DOAS) it is possible to obtain concentrations of O3 and SO2 and by a subtraction technique their contribution to the absorption are eliminated. The method was tested during an ozone LIDAR intercomparison campaign, TROLIX, in the Netherlands, 1991. In this field experiment spectrally resolved particle extinction was measured as well as O3 and SO2 concentrations, and the results were compared with LIDAR and point monitor measurements. The dual path method also has the potential to improve the detection limit in long path absorption measurements of gas concentration. By ratioing spectra from two different pathlengths instrument factors are cancelled and detection limits may be improved. An example demonstrating improvement in ozone long path measurements is given.

Paper Details

Date Published: 12 February 1993
PDF: 9 pages
Proc. SPIE 1715, Optical Methods in Atmospheric Chemistry, (12 February 1993); doi: 10.1117/12.140185
Show Author Affiliations
Bo Galle, Swedish Environmental Research Institute (Sweden)
Johan M. Mellqvist, Swedish Environmental Research Institute (Sweden)

Published in SPIE Proceedings Vol. 1715:
Optical Methods in Atmospheric Chemistry
Harold I. Schiff; Ulrich Platt, Editor(s)

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