Review of aerosol light absorption measurement

The measurement of aerosol light absorption with commonly-used filter-based techniques needs to be better quantified with "first-principle" in situ methods in both laboratory and field studies. The first principle measurement of aerosol light absorption is most closely approximated by photoacoustic and extinction-minus-scattering techniques. Photoacoustic techniques need to be better characterized for the measurement of aerosol light absorption for particles with semi-volatile components and multi-wavelength photoacoustic instruments need to be more commonly used. While high-sensitivity extinction-minus-scattering techniques utilizing CRD with multi-kilometer absorption paths are becoming available, their accuracy still needs to be quantified with a variety of ambient source and laboratory aerosols. Our understanding of the advantages and shortcomings of aerosol light absorption measurement techniques also needs to be improved through additional experimental closure studies (extinction = scattering + absorption), which recently have become feasible for low concentration ambient aerosols by using CRD techniques for extinction measurements. Further discussion has been given by Moosmüller et al.