Tc. Bond et al., Calibration and intercomparison of filter-based measurements of visible light absorption by aerosols, AEROS SCI T, 30(6), 1999, pp. 582-600
Data on light absorption by atmospheric particles are scarce relative to th
e need for global characterization. Most of the existing data come from met
hods that measure the change in light transmission through a filter on whic
h particles are collected. We present a calibration of a recently developed
filter-based instrument for continuous measurement of light absorption (mo
del PSAP, Radiance Research, Seattle, WA) that has been incorporated in sev
eral measurement programs. This calibration uses a reference absorption det
ermined as the difference between light extinction and light scattering by
unaltered (suspended) particles. In addition, we perform the same calibrati
on for two other common filter-based methods: an Integrating Plate and the
Hybrid Integrating Plate System, For each method, we assess the responses t
o both particulate light scattering and particulate light absorption. We fi
nd that each of the instruments exhibits a significant response to nonabsor
bing aerosols and overestimates absorption at 550 nm by suspended particles
by about 20-30 %. We also present correction factors for the use of the PS
AP.