Long-path method for measurement of spectrally resolved particle attenuation

Bo Galle; Johan M. Mellqvist

doi:10.1117/12.140185

12 February 1993 Long-path method for measurement of spectrally resolved particle attenuation

Bo Galle, Johan M. Mellqvist

Proceedings Volume 1715, Optical Methods in Atmospheric Chemistry; (1993) https://doi.org/10.1117/12.140185
Event: Environmental Sensing '92, 1992, Berlin, Germany

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.

Citation Download Citation

Bo Galle and Johan M. Mellqvist "Long-path method for measurement of spectrally resolved particle attenuation", Proc. SPIE 1715, Optical Methods in Atmospheric Chemistry, (12 February 1993); https://doi.org/10.1117/12.140185

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