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Atmospheric Measurement Techniques An interactive open-access journal of the European Geosciences Union
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Discussion papers
https://doi.org/10.5194/amt-2018-411
© Author(s) 2019. This work is distributed under
the Creative Commons Attribution 4.0 License.
https://doi.org/10.5194/amt-2018-411
© Author(s) 2019. This work is distributed under
the Creative Commons Attribution 4.0 License.

Research article 14 Jan 2019

Research article | 14 Jan 2019

Review status
This discussion paper is a preprint. A revision of this manuscript was accepted for the journal Atmospheric Measurement Techniques (AMT) and is expected to appear here in due course.

Evaluating biases in filter-based aerosol absorption measurements using photoacoustic spectroscopy

Nicholas W. Davies1,2, Cathryn Fox2, Kate Szpek2, Michael I. Cotterell1,2, Jonathan W. Taylor3, James D. Allan3,4, Paul I. Williams3,4, Jamie Trembath5, Jim M. Haywood1,6, 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
  • 3Centre for Atmospheric Science, School of Earth and Environmental Sciences, University of Manchester, Manchester, M13 9PL, UK
  • 4National Centre for Atmospheric Science, University of Manchester, Manchester, M13 9PL, UK
  • 5Facility for Airborne Atmospheric Measurements, Cranfield, MK43 0AL, UK
  • 6Earth System and Mitigation Science, Met Office Hadley Centre, Exeter, EX1 3PB, UK

Abstract. Biases in absorption coefficients measured using a filter-based absorption photometer (Tricolor Absorption Photometer, or TAP) at wavelengths of 467, 528 and 652 nm are evaluated by comparing to measurements made using photoacoustic spectroscopy (PAS). We report comparisons for ambient sampling covering a range of aerosol types including urban, fresh biomass burning and aged biomass burning. Data are also used to evaluate the performance of three different TAP correction schemes. We found that photoacoustic and filter-based measurements were well correlated, but filter-based measurements generally overestimated absorption by up to 45 %. Biases varied with wavelength and depended on the correction scheme applied. Optimal agreement to PAS data was achieved by processing the filter-based measurements using the recently developed correction scheme of Müller et al. (2014), which consistently reduced biases to 0–17 % at all wavelengths. The biases were found to be a function of the ratio of organic aerosol mass to light-absorbing carbon mass although applying the Müller et al. (2014) correction scheme to filter-based absorption measurements reduced the biases and the strength of this correlation significantly. Filter-based absorption measurement biases led to aerosol single-scattering albedos that were biased low by up to 0.07 and absorption Ångström exponents (AAE) that were in error by ±0.54. The discrepancy between the filter-based and PAS absorption measurements is lower than reported in some earlier studies, and points to a strong dependence of filter-based measurement accuracy on aerosol source type.

Nicholas W. Davies et al.
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Interactive discussion
Status: closed
Status: closed
AC: Author comment | RC: Referee comment | SC: Short comment | EC: Editor comment
Printer-friendly Version - Printer-friendly version Supplement - Supplement
Nicholas W. Davies et al.
Nicholas W. Davies et al.
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Short summary
This research project assesses biases in traditional, filter-based, aerosol absorption measurements by comparison to state of the art, non-filter-based, or in-situ, measurements. We assess biases in traditional absorption measurements for three main aerosol types, including dust, fresh and aged biomass burning aerosols. The main results of this study are that the traditional and state of the art absorption measurements are well correlated and that biases in the former are up to 45 %.
This research project assesses biases in traditional, filter-based, aerosol absorption...
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