stanBC
Published June 2, 2026 | Version v1
Project deliverable Open

Report on the determination of wavelength-dependent MAC values and wavelength dependent filter-based light absorption photometer calibration factors including multiple scattering factors, with their associated measurement uncertainties (target uncertainties < 15 % for 95 % confidence level) based on the calibration in D5

Authors/Creators

  • 1. EDMO icon Leibniz-Institute for Tropospheric Research
  • 2. ROR icon Finnish Meteorological Institute
  • 3. ROR icon National Physical Laboratory
  • 4. National Research Council Canada
  • 5. Aerosol d.o.o.
  • 6. ROR icon National Centre of Scientific Research "Demokritos"
  • 7. ROR icon FHNW University of Applied Sciences and Arts Northwestern Switzerland
  • 8. Haze Instruments d.o.o.
  • 9. ROR icon University of Nova Gorica
  • 10. ROR icon Jožef Stefan Institute
  • 11. ROR icon Swiss Federal Institute of Metrology
  • 12. ROR icon Physikalisch-Technische Bundesanstalt

Description

This study presents wavelength-dependent mass absorption cross sections (MAC) and calibration factors for filter-based photometers derived from controlled laboratory experiments with well-characterized aerosols. Using soot particles with varying coating thickness, MAC is evaluated as a function of single scattering albedo (SSA). Compared to common core-shell model predictions, MAC can grow less or even decrease with increasing coating, suggesting that morphological changes, such as restructuring and non-ideal mixing states, can suppress the expected lensing effect. Comparisons with optical models indicate
better agreement with fractal and porous particle representations than with idealized core–shell structures. These findings emphasize the importance of particle morphology and growth pathways for interpreting aerosol absorption and improving photometer calibration.


The wavelength dependence of the MAC agrees better with expectations, since the higher imaginary part  of the refractive index in the UV, compared to the red or near-infrared wavelengths of organic matter, leads to stronger UV absorption, independent of morphological effects.

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22NRM02 stanBC - Deliverable D6.pdf

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