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Atmospheric Measurement Techniques An interactive open-access journal of the European Geosciences Union
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Volume 11, issue 4 | Copyright
Atmos. Meas. Tech., 11, 2313-2324, 2018
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.

Research article 24 Apr 2018

Research article | 24 Apr 2018

On the accuracy of aerosol photoacoustic spectrometer calibrations using absorption by ozone

Nicholas W. Davies1,2, Michael I. Cotterell1,2, Cathryn Fox2, Kate Szpek2, Jim M. Haywood1,3, and Justin M. Langridge2 Nicholas W. Davies et al.
  • 1College of Engineering, Mathematics and Physical Sciences, University of Exeter, Exeter, EX4 4QF, UK
  • 2Observation Based Research, Met Office, Exeter, EX1 3PB, UK
  • 3Earth System and Mitigation Science, Met Office Hadley Centre, Exeter, EX1 3PB, UK

Abstract. In recent years, photoacoustic spectroscopy has emerged as an invaluable tool for the accurate measurement of light absorption by atmospheric aerosol. Photoacoustic instruments require calibration, which can be achieved by measuring the photoacoustic signal generated by known quantities of gaseous ozone. Recent work has questioned the validity of this approach at short visible wavelengths (404nm), indicating systematic calibration errors of the order of a factor of 2. We revisit this result and test the validity of the ozone calibration method using a suite of multipass photoacoustic cells operating at wavelengths 405, 514 and 658nm. Using aerosolised nigrosin with mobility-selected diameters in the range 250–425nm, we demonstrate excellent agreement between measured and modelled ensemble absorption cross sections at all wavelengths, thus demonstrating the validity of the ozone-based calibration method for aerosol photoacoustic spectroscopy at visible wavelengths.

Publications Copernicus
Short summary
The poorly characterised optical properties of atmospheric aerosols are one of the major uncertainties when modelling future climate change. Photoacoustic spectroscopy is an accurate and sensitive method for measurement of aerosol light absorption. Photoacoustic spectrometers require calibration; hence this study validates the use of ozone as a calibrant and simultaneously verifies the accuracy of the photoacoustic spectrometers in question.
The poorly characterised optical properties of atmospheric aerosols are one of the major...